THE UNIVERSITY 
 
 OF ILLINOIS 
 
 LIBRARY 
 
 OL 551.22 
 D W67s 
 
\ 
 
 Return this book on or before the 
 Latest Date stamped below. 
 
 Theft, mutilation, and underlining of books 
 are reasons for disciplinary action and may 
 result in dismissal from the University. 
 University of Illinois Library 
 
 n 
 
 I" 
 i u u 
 
 Ob' 
 
 HQV I 2 1966 
 
 JUN 2| 
 
 JUiLDING 
 
 JUN 
 
 12001 
 
 
 21 2001 
 
 L161—0-1096 
 
Digitized by the Internet Archive 
 in 2019 with funding from 
 University of Illinois Urbana-Champaign 
 
 https://archive.org/details/studiesincomparaOOwill 
 
CARNEGIE INSTITUTION OF WASHINGTON 
 
 Publication No. 382 
 
 1929 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Frontispiece 
 
 o 
 
 
 -4—> 
 
 c; 
 
 o 
 
 £3 
 
 o 
 
 O 
 
 
 u 
 
 
 be 
 
 ro 
 
 D 
 
 
 t- 
 
 
 O 
 
 -+—> 
 
 
 d 
 
 
 d 
 
 r-i 
 
 
 • 
 
 o 
 
 r- 
 
 c 
 
 o 
 
 O 
 
 LT) 
 
 c 
 
 t—> 
 
 03 
 
 
 U 
 
 o 
 
 
 
 a 
 
 o 
 
 D 
 
 O 
 
 c 
 
 
 o 
 
 l—i 
 
 of 
 
 
 ►“- 1 
 
 c/3 
 
 
 D 
 
 5 
 
 
 u 
 
 •*-' 
 
 
 D 
 
 be 
 
 D 
 
 u. 
 
 X 
 
 *5d 
 
 ■*“* 
 
 c 
 
 C/3 
 
 03 
 
 l-H 
 
 C/3 
 
 
 
 C/3 
 
 U 
 
 r-* 
 
 f" 
 
 # o 
 
 u 
 
 -4—> 
 
 a; 
 
 03 
 
 . > 
 
 > 
 
 O 
 
 JD 
 
 
 D 
 
 X 
 
 
 
 03 
 
 
 
 d 
 
 
 
 r - 1 
 
 03 
 
 J3 
 
 0/ 
 
 x 
 
 *3 
 
 D 
 
 Uh 
 
 u 
 
 
 a; 
 
 03 
 
 u 
 
 
 03 
 
 
 
 03 
 
 u 
 
 
 D 
 
 03 
 
 > 
 
 V- 
 
 O 
 
 c/3 
 
 c/3 
 
 D 
 
 D 
 
 £ 
 
 
 
 > 
 
 
 
 3 
 
 D 
 
 O 
 
 > 
 
 C/3 
 
 
 be 
 
 D 
 
 r~ 
 
 r-i 
 
 4-* 
 
 3 
 
 £ 
 
 o 
 
 • «—• 
 
 
 
 
 «— 
 
 03 " 
 
 03 
 
 u 
 
 
 D 
 
 C/3 
 
 
 d 
 
 03 
 
 C 
 
 u, 
 
 O 
 
 0 
 
 C/3 
 
 u 
 
 a/ 
 
 
 
 
 X 
 
 > 
 
 
 0 
 
 X 
 
 "2 
 
 03 
 
 03 
 
 C/3 
 
 O 
 
 c r 
 CD 
 
 
 
 03 
 
 03 
 
 i~ 
 
 p£J 
 
 u 
 
 C/3 
 
 <u 
 
 
 U 
 
 o3 
 
 c n 
 
 ■ ^ 
 
 O 
 
 c 
 
 C/3 
 
 O 
 
 03 
 
 Ph 
 
 u 
 
 O 
 
 D 
 
 ' U 
 
 £ 
 
 0/ 
 
 CD 
 
 
 u 
 
 u 
 
 03 
 
 
 C/3 
 
 >> 
 
 X 
 
 
 0 
 
 13 
 
 0 
 
 u 
 
 u 
 
 
 0 
 
 iD 
 
 
 
 h-^ 
 
 
 
 H 
 
 c/3 
 
 
 0 
 
 
 o 
 
 lO 
 
 is Quebrada Asientos. Official photograph, Potrerillos Company. 
 
STUDIES IN COMPARATIVE 
 SEISMOLOGY 
 
 EARTHQUAKE CONDITIONS 
 
 IN CHILE 
 
 o 
 
 BY 
 
 BAILEY WILLIS 
 
 Research Associate in Seismology 
 Carnegie Institution of Washington 
 
 WITH CONTRIBUTIONS BY 
 
 J. B. Macelwane, S.J-, Perry Byerly, Johannes Felsch, and 
 
 H. S. Washington 
 
 Published by Carnegie Institution of Washington 
 
 Washington, 1929 
 
Introduction 
 
 TABLE OF CONTENTS 
 
 PAGE 
 
 I 
 
 SECTION I 
 
 Earthquakes, Their Historical Sequence and Effects in Atacama 
 
 Regional Description of Atacama. 7 
 
 Earthquake History of Atacama. 14 
 
 List of severe earthquakes, 1543-1922, inclusive. 14 
 
 Descriptions of terremotos, 1543-1918, inclusive. 14 
 
 Terremoto of November 1922. 26 
 
 Immediate antecedents . 26 
 
 Experiences in the terremoto. 29 
 
 Dr. Luis Sierra Vera, at Copiapo. 29 
 
 Questionnaires . 29 
 
 Residents of La Serena . 29 
 
 Residents of Coquimbo . 31 
 
 Residents of Vallenar .. 31 
 
 Residents of Freirina. 31 
 
 Residents of Huasco . 34 
 
 Residents of Caldera . 34 
 
 Residents of Chanaral . 35 
 
 Residents of Copiapo . 35 
 
 Residents of Tierra Amarilla. 38 
 
 Residents of Puquios. 38 
 
 Residents of Salado . 39 
 
 Residents of Potrerillos . 39 
 
 Effects on monuments. 39 
 
 Surface evidences of faulting. 41 
 
 Distribution of intensities. 42 
 
 Studies of tapiales. 45 
 
 SECTION II 
 
 Geologic Facts, Their Historical Development and Dynamic History 
 
 Rocks of Atacama. 51 
 
 Dynamic History of Atacama . 52 
 
 Point of view. 52 
 
 Paleozoic activities . 52 
 
 Mesozoic activities. 61 
 
 Tertiary and later activities. 63 
 
 General geographic relations. 66 
 
 Investigation of the Earthquake Mechanism. 68 
 
 Method of attack. 68 
 
 Hypothesis of earthquake action. 7 ° 
 
 Evidences of pressure. 75 
 
 General statement . 75 
 
 Overthrusts at Potrerillos. 75 
 
 Structural conditions at Chuquicamata. 79 
 
 V 
 
 684902 
 
VI 
 
 Table of Contents 
 
 PAGE 
 
 Events of Post-Cretaceous Time. 83 
 
 Physiographic interpretation . 83 
 
 Tertiary matureland . 85 
 
 Epoch of canyon development. 91 
 
 Gravel deposits . 93 
 
 Evidences of glaciation. 98 
 
 Geology of Coquimbo Bay . 101 
 
 General statement . 101 
 
 The terraces. 103 
 
 Report on Fossils from Coquimbo, by Eric Jordan. 117 
 
 Introduction. 117 
 
 Species recognized from each locality . 117 
 
 Species recognized from the Pliocene and Pleistocene of Coquimbo. 118 
 
 Discussion . 118 
 
 Pleistocene . 118 
 
 Pliocene . 118 
 
 Summary . 119 
 
 San Felix and San Ambrosio. 120 
 
 General description and geology, by Bailey Willis. 120 
 
 Petrology of San Felix, by H. S. Washington. 125 
 
 General statement . 125 
 
 Trachyte . 125 
 
 Hyalo-trachyte . 126 
 
 Nephelite basanite. 127 
 
 Tuff . 129 
 
 General conclusions. 131 
 
 Basalt of San Ambrosio. 132 
 
 APPENDICES 
 
 Appendix I—Report on Seismograms, by J. B. Macelwane, S. J., and Perry Byerly. 135 
 
 Appendix II—Distribution of Intensities, by Luis Sierra Vera. 141 
 
 Appendix III—Geology of Atacama, by Johannes Felsch. 149 
 
 Appendix IV—Geologic Notes, by Bailey Willis. 157 
 
 Appendix V—Petrographic Sketch, by Henry S. Washington. iyi 
 
 Index . 177 
 
ILLUSTRATIONS 
 
 PLATES 
 
 PAGE 
 
 Frontispiece. Potrerillos. Locality called Pastos Cerrados above Cortadera, looking southwest over mature- 
 
 land at elevations ranging from 12,000 to 15,000 feet (3,500 to 4,500 meters). The rocks 
 are Neocomian shales and limestones, and in the view the strata are repeated by over¬ 
 thrusts three times. Deep canyon in foreground is Quebrada Asientos. Official photo¬ 
 graph, Potrerillos Company . Ill 
 
 Plate I A. Copiapo. General view of Copiapo basin and city. Area of greatest destruction lies in 
 distant middle ground to right of church in center of picture. This is the area of 
 marshy formations. There was less destruction in left (eastern) half of city, which is 
 on slope of alluvial cone. Hills in right (western) half of panorama are Paleozoic 
 rocks and belong to Coast range. Those on left (east) are of Mesozoic rock and con¬ 
 stitute foothills of the Andes. Paipote at mouth of the Quebrada Paipote, where it 
 
 joins the Copiapo valley, lies in extreme middle distance. 4 
 
 IB. Coast range between Pueblo Hundido and Chanaral. The dark rocks which form 
 heights of distant hill are Paleozoic slates and schists; light-colored masses are intru¬ 
 sive granite. High ridge in middle foreground shows outcrop of a large dike of black 
 diabase, probably also of Paleozoic age. The view illustrates the characteristic struc¬ 
 
 ture of Coast range of Atacama..... 4 
 
 II A. Coquimbo. Looking north across district swept by earthquake wave. 8 
 
 B. Coquimbo. Looking south to low district, swept by earthquake wave. 8 
 
 III A. Coquimbo. Effects of earthquake wave in railroad yard; height of wave 26 feet (8 
 
 meters), above mean tide. 8 
 
 B. Coquimbo. View from hill south of bay, looking northwest across flat swept by earth¬ 
 quake wave . 8 
 
 IV A. Near Coquimbo. Hut, on coast 16 miles (25 km.) south of city, not damaged by earth¬ 
 
 quake, showing weakness of shock at this point. 10 
 
 B. Coquimbo. Jointed Paleozoic granite near northern end of promontory. 10 
 
 V A. Vallenar. Water forced out of river bed by shaking down of alluvium. 12 
 
 B. Vallenar. Two-story frame and adobe house standing among ruins of one-story massive 
 
 adobe houses . 12 
 
 VI A. Copiapo. Typical adobe ruin . 12 
 
 B. Copiapo. Good adobe ruined by heavy mud roof. 12 
 
 VII A. Copiapo. Adobe wall of large building intact, tied with timbers; tapiales thrown down, 
 
 temporary shelter of rushes. 42 
 
 B. Tatara. Estancia west of Vallenar, near fault line; adobe buildings wrecked. 42 
 
 VIII A and B. Vallenar, (12.5 miles (20 km.) southwest of). Examples of effect of the earth¬ 
 quake upon massive structures of dry stone walls; located on gravel plain above fault. 42 
 
 IX A. Vallenar. Church tower intact . 42 
 
 B. Vallenar. Walls of church, showing columns and walls of cana de Guayaquil on frame 
 
 construction . 42 
 
 X. Effects of shock on tall buildings: 
 
 A. Church in Plaza Godoy. A frame structure, interior walls and plaster crushed. 42 
 
 B. Smelter structure at Huasco. Note twisting effect at node of vibration. 42 
 
 XI A. Copiapo. Destruction of tombs of massive masonry. 42 
 
 B. Vallenar. Ruins after the removal of the dead and wounded, victims of ignorance and 
 
 carelessness, who numbered 1,300, nearly one-third of the population. 42 
 
 XII A. First-class construction of frame and “brea” or brush; to be plastered with mud. 42 
 
 B. Average construction of frame, caha de Guayaquil, and adobe; to be plastered with mud. 42 
 
 XIII A. Upper Copiapo valley, San Antonio. Rebuilding a wall of tapiales. 42 
 
 B. Upper Huasco valley, La Pampa. Very old adobe house with mud roof. 42 
 
 XIV A. Vallenar. Wall of tapiales; two high, partly thrown. 42 
 
 B. Vallenar. Typical ruin of adobe house with heavy mud-covered roof; front wall pushed 
 
 out by rafters . 42 
 
 XV A. Upper Copiapo valley, San Antonio. Looking northwest, showing general destruction of 
 
 adobe houses . 42 
 
 B. Upper Copiapo valley, San Antonio. Looking southwest, showing general ruin and a new 
 
 wall of tapiales. 4 2 
 
 VII 
 
VIII 
 
 Illustrations 
 
 PAGE 
 
 XVI A. Upper Copiapo valley, San Antonio. Cemetery walls standing on east, west, and south, 
 
 on gravel cone inside canyon; white rhyolite dike in Jurassic sandstone. 42 
 
 B. Upper Copiapo valley, San Antonio. View up valley, showing broad, marshy fill on 
 
 which village stands . 42 
 
 XVII A. Upper Copiapo valley, Potrero Seco. Walls of tapiales thrown down, gate columns stand¬ 
 ing; typical view of wide canyon. 42 
 
 B. Upper Copiapo valley, at La Sureta. A primitive plough consisting of a tree-trunk and 
 
 roots . 42 
 
 XVIII A. La Pampa on Rio Elqui. Wall thrown and column standing. 42 
 
 B. La Pampa on Rio Elqui. Columns and roof free to sway but not overthrown. 42 
 
 XIX A. Copiapo. Atacama monument, showing statue thrown 16 feet (5 meters) from its 
 
 pedestal . 42 
 
 B. Copiapo. Base of Atacama monument, showing detail of brick layer sheared by rotation 
 
 of upper structure . 42 
 
 XX A. Copiapo. Overthrow of Matti monument by failure of pedestal. 42 
 
 B. Vicuna. Monument in park, not disturbed. 42 
 
 XXI A. Vallenar. Rock fall on track up Huasco valley, near Quebrada Jilguero and fault line.. 42 
 
 B. Vallenar. Railroad up Huasco valley, showing displacement of track. 42 
 
 XXII A. Vallenar. Quebrada Jilguero, 3 miles (5 km.) east; view of cliff at outlet of the que¬ 
 brada into valley of Rio Huasco, showing earthquake cracks opened in last shock.... 42 
 B. Vallenar. Quebrada Jilguero, looking through canyon by which it enters the Huasco. 
 
 On left is cliff which was fractured by earthquake, and in foreground is reinforced 
 concrete bridge that was not injured. 42 
 
 XXIII A. Vallenar. Quebrada Valparaiso, general view of big slide. 42 
 
 B. Vallenar. Quebrada Valparaiso, view of quebrada showing position of big slide with 
 
 reference to terrace level as seen across Huasco valley. 42 
 
 XXIV A. Vallenar (2 miles west of). Slide in Quebrada Valparaiso, in Pleistocene terrace gravels, 
 
 looking north . 42 
 
 B. Vallenar. Slide in Quebrada Valparaiso, looking north from near middle of slide. 42 
 
 XXV A. Vallenar. Quebrada Valparaiso, details of big slide showing old mass shaken down in 
 
 previous earthquakes and view across terraces of Huasco valley. 42 
 
 B. Vallenar. Quebrada Valparaiso, view of old slide, showing breaking down of mass in 
 
 last earthquake . 42 
 
 XXVI A. Vallenar. Slide in Quebrada Valparaiso; near view of striated surface in Pleistocene 
 
 gravels . 42 
 
 B. Vallenar. Looking south across Rio Huasco from Quebrada Valparaiso along fault line. 42 
 
 XXVII A. Copiapo. Detailed view of tapiale wall, which runs NW.-SE. 46 
 
 B. Copiapo. General view of tapiale wall running NW.-SE. and of distant wall at right 
 
 angles to it, showing effect of earthquake. 46 
 
 XXVIII A. Copiapo. Field in valley, southwest of city; wall of tapiales extending southwest. 46 
 
 B. Copiapo. Same field as in upper view; wall of tapiales extending southeast. 46 
 
 XXIX A. Copiapo valley, above Copiapo near Tierra Amarilla. Showing standing and fallen 
 
 tapiales; looking south parallel to longitudinal earthquake waves. 46 
 
 B. Copiapo valley, below Copiapo at Ramadillas. Showing wall of tapiales running N.-S., 
 
 parallel to longitudinal earthquake waves. 46 
 
 XXX A. Vallenar. Wall of tapiales near the city, extending east across the line of longitudinal 
 
 vibrations . 46 
 
 B. Vallenar. Narrows in the valley of the Rio Huasco caused by a fault-ridge of Paleozoic 
 
 rocks; looking west, down stream toward the city. 46 
 
 XXXI A. Copiapo. Fruit dish, showing the two hind legs, indicated by white points, on which it 
 
 danced on sideboard as shown in XXXII B. 46 
 
 B. Copiapo. Matta sideboard and fruit dish which made record of gyrations shown in plate 
 
 XXXIIB . 46 
 
 XXXII A. Copiapo. Matta sideboard; the fruit dish that danced. 46 
 
 B. Copiapo. Matta sideboard; the record it wrote in zig-zagging on the polished surface and 
 
 in sliding straight down and off. 46 
 
 XXXIII A. Copiapo. Adobe house 70 years old, wrecked by collapse of roof; outer walls suffered 
 but little, being held together by beams of ceiling which may be seen projecting 
 through. Foundation material is river gravel, but bed-rock lies not far below surface. 48 
 B. Copiapo. Adobe house of one story with light roof, built around a square patio, show¬ 
 ing shearing of walls on vertical lines. House was rendered uninhabitable by general 
 
 fall of plaster walls and ceiling. 48 
 
 XXXIV A. Near Toledo, 2 miles west of Copiapo. Looking S. 62° E. on line of shearing, showing 
 
 crushing, probably on a fault. 54 
 
 B. Vallenar, 19 miles south of. Paleozoic granite, showing jointing but not crushing, being 
 
 off any fault line. 54 
 
Illustrations 
 
 ix 
 
 PAGE 
 
 XXXV A. The Andes southeast of Santiago. Valley of Rio Vulcano, showing Jurassic lavas up¬ 
 turned to vertical dips. 60 
 
 B. The Andes southeast of Santiago. Valley of Rio Vulcano, showing Jurassic lavas lying 
 
 in horizontal position . 60 
 
 XXXVI A. Upper Copiapo valley. View of minor upthrust or ramp in Mesozoic eruptives. Beds 
 
 dragged up . 62 
 
 B. Chuquicamata. View of footwall of ore deposit showing horizontal striae on footwall 
 
 fault. The ore body in front of footwall moved to right. 62 
 
 XXXVII A. Quebrada de Paipote, near Puquios. Thrust faults in Jurassic limestone and intrusives. 66 
 B. Quebrada de Paipote, La Puerta. Massive flows of labradorite porphyry of Jurassic age 
 
 upturned to steep angle. 66 
 
 XXXVIII A. Quebrada de Paipote, near La Puerta. Conformable sequence of Jurassic sediments and 
 
 lava flows . 74 
 
 B. Quebrada de Paipote, near La Puerta. Faulted Jurassic sediments with ravine developed 
 
 on fault zone . 74 
 
 XXXIX. Potrerillos, Quebrada Asientos. Overthrust in Neocomian limestone and shale series.... 74 
 XL A. Potrerillos, Quebrada Asientos. Normal sequence of Neocomian limestone and shale; 
 
 cross-bedded limestone . 74 
 
 B. Potrerillos, Quebrada Asientos. Neocomian limestone deposited on granite with basal 
 
 layer of arkose sandstone. 74 
 
 XLI A and B. Potrerillos, Quebrada Asientos. Views of Neocomian limestone in the zone of 
 
 thrust faults . 74 
 
 XLII. Geologic traverse and section of thrusts exposed in Quebrada Asientos, Potrerillos.... 74 
 XLIII A. Salar de Infieles. Salt basin on fault zone northeast of Potrerillos; elevation about 13,000 
 
 feet (4,000 meters) ; Cerro de Infieles (16,570 feet), looking north. 84 
 
 B. Salar de Pedernales. Large salt basin occupying wide valley in Andean plateau, north¬ 
 west of Potrerillos; elevations 11,500 to 13,000 feet (3,500 to 4,000 meters) looking 
 
 south . 84 
 
 XLIV A. Potrerillos matureland northeast of. 11,500 to 13,000 feet above sea; Pliocene (?) 
 
 volcano, Dona Ynez, 16,730 feet (5,070 meters), in left center. 84 
 
 B. Potrerillos, Quebrada Asientos. Fringing gravels, cemented; elevation 10,000 feet (3,000 
 
 meters) . 84 
 
 XLV A. Desert and Puna of Atacama (after Bowman). 84 
 
 B. Puna of Atacama (after Bowman). 84 
 
 XLVI. Potrerillos, Elevation 10,400 feet (3,100 meters) ; terrace of fringing gravels which slopes 
 
 down, unbroken, to Pueblo Hundido at the western base of the Andes. 84 
 
 XLVII. Copiapo. Wind-fretted pebbles from highest terrace west of Paipote in the Copiapo basin. 84 
 XL VIII A. River silt in the Copiapo basin, unusually well jointed for unconsolidated Pleistocene 
 
 deposits . 84 
 
 B. The Andes, 20 miles southeast of Santiago. Granite pinnacle in center with Jurassic lava 
 
 flows abutting on right. 84 
 
 XLIXA. Huasco valley, 7 miles west of Vallenar. Looking north up longitudinal valley; Coast 
 
 range of Paleozoic rocks on left; mantling gravels (Pliocene?) in bluffs. 84 
 
 B. Rio Huasco (headwaters of). Cliffs of gravel (Pliocene?) above Laguna Grande; 
 height 1,000 feet (300 meters) estimated; lower slopes are slides, effect of active 
 
 fault . 84 
 
 LA. Copiapo valley, near Monte Amargo. Interbedded sands and peat beds in river valley... 84 
 
 B. Copiapo valley, near Monte Amargo. Peat digging. 84 
 
 LI. Potrerillos. Bed of Potrerillos glacierette, on railroad above mining camp, elevation 
 
 11,000 feet (3,300 meters). Official photograph, Andes Copper Company, Potrerillos.. 84 
 LII. Potrerillos. Bed of Potrerillos glacierette, near view. Official photograph, Andes Copper 
 
 Company, Potrerillos . 84 
 
 LIII A. Vallenar. Close view of gravels exposed in road-cut, showing steeply inclined stratifi¬ 
 cation . 84 
 
 B. Quebrada de Hielo, 50 miles northeast of Copiapo. Limestone erratics lying on plain of 
 Tertiary tuff, elevation about 3,600 feet (1,400 meters) ; rocks show glacial striae and 
 indicate former existence of glaciers on high peaks farther east. They may have been 
 
 transported to their present position by floating ice or by cloudbursts. 84 
 
 LIV A. Coquimbo. Looking east from Coquimbo point past La Herradura to Pliocene terraces 
 
 along Coast range; jointed Paleozoic granite in foreground. 84 
 
 B. Coquimbo. Looking northwest from Coquimbo point, showing broad, wave-cut bench and 
 
 cliff facing Pacific . 84 
 
 LV. Chart of Coquimbo Bay. 106 
 
 LVI. Coquimbo. Arroyo Gulebron. General view looking north toward bluffs of Pliocene 
 
 sediments . 10 8 
 
X 
 
 Illustrations 
 
 PAGE 
 
 LVII A. Coquimbo. Quebrada Gulebron. Marine Pliocene at base of cliffs. 108 
 
 B. Coquimbo. Quebrada Gulebron. Secondary limestone capping upper terrace; described 
 
 by Darwin as “losa”. 108 
 
 LVII I A. Coquimbo. Quebrada Gulebron. Upper terrace near Estancia San Martin, showing upper 
 horizon of erratics in marine strata; the lower horizon is just below the bottom cf 
 
 the view . 108 
 
 B. Coquimbo. Quebrada Gulebron. Cliffs on south side showing large erratic in marine 
 
 strata in center of view. 108 
 
 LIX A. Coquimbo. Pliocene, marine strata with embedded erratic; the tripod is one meter long; 
 
 looking south at cliffs south of the Quebrada Gulebron. 108 
 
 B. Coquimbo. Near view of same large erratic in Pliocene strata south of Quebrada 
 
 Gulebron . 108 
 
 LX A. Coquimbo. Quebrada Gulebron. Rock gorge from which erratics were presumably 
 
 derived . 108 
 
 B. Coquimbo. Quebrada Gulebron. South bank in which erratics occur embedded; very 
 
 large erratic in foreground; about 23 feet long by 12 feet high (7 meters by 4 meters). 108 
 LXI A. Coquimbo. Looking south past the curve of La Herradura cove. Large boulder buried 
 in marine Pliocene on the terrace 100 feet above sea, 1.5 miles west of the Quebrada 
 
 Gulebron . 108 
 
 B. Coquimbo. Marine strata with embedded boulder; locality in the railroad cut east of 
 
 La Herradura cove . 108 
 
 LXI I A. Coquimbo. Marine sediments on granite promontory west of bay, just above town, look¬ 
 ing south . 118 
 
 B. Coquimbo. Marine sediments, just above town; near view, looking into artificial cave.. 118 
 
 LXIII A. Coquimbo. Black point above town; a mass of boulders in place in the decayed surface 
 
 of the diabase dike. 118 
 
 B. Coquimbo. Wave-cut bench marking high level of sea on granite islet, which is now 
 
 western side of bay; boulders of black diabase moved along beach. 118 
 
 LXIV A. San Ambrosio. Near view of southwest cliff, showing bedded lavas and vertical dikes.. 122 
 
 B. San Ambrosio. From the west in silhouette against the morning sun. 122 
 
 LXV A. Isla San Felix. Looking east over anchorage to basalt pinnacles known as the Catedral de 
 
 Peterborough . 122 
 
 B. San Ambrosio. From the southeast. 122 
 
 LXVI A. Isla San Felix. Cerro Amarillo, the hill of yellow tuff, as seen from black lava flow look¬ 
 ing north; height of Cerro 660 feet (200 meters). 122 
 
 B. Isla San Felix. Western base of Cerro Amarillo, sloping into crater showing structure 
 
 of tuff . 122 
 
 LXVII A. Isla San Felix. Cave at junction of younger black lava flow with older tuff of Cerro 
 
 Amarillo . 122 
 
 B. Isla San Felix. Looking south from Cerro Amarillo over recent black lava flow; Isla 
 
 San Ambrosio in distance; Isla Gonzales on right. 122 
 
 LXVIII A. Isla San Felix. View of island, looking south from ship at anchor. On right is Cerro 
 Amarillo, 660 feet high; toward left stretches plateau of recent basalt flows; at con¬ 
 tact of basalt with tuff hill the waves have eroded a large cave. Only feasible landing 
 
 is on wave-cut shelf at right of cave. 122 
 
 B. Isla San Felix. Looking southeast from Cerro Amarillo over lava plateau of recent basalt 
 flows. The crescent, which terminates in island at right, surrounds about two-fifths of 
 
 crater. In distance is seen the Isla San Ambrosio. 122 
 
 LXIX A. Vallenar. View of valley looking up Huasco river toward the foothills of the Andes; 
 
 showing high terrace south of river.Pocket 
 
 B. Vallenar. Looking north; view of Huasco valley and broad plain which lies between 
 Coast Range on left and foothills of Andes on right; showing successive terrace levels 
 by which the slope rises in three steps to height of 660 feet (200 meters) above 
 
 river .Pocket 
 
 LXX A. Upper Copiapo valley. View from southeast to south and west. On left is Cerro La- 
 drillos, composed of Jurassic lavas and forming western foothills of Andes. Upper 
 Copiapo valley extends into distance southward. High hills behind trees consist chiefly 
 of Paleozoic granite and diabase. On right is upper portion of basin of Copiapo and 
 
 locality called Paipote .Pocket 
 
 B. Vicuna. Panoramic view of Rio Elqui, comprising heights of Andes on left and city of 
 Vicuna on right. At this point the Jurassic lavas form an anticline; there are no 
 faults, and the city, although built in the river plain, suffered but little damage.Pocket 
 
Illustrations 
 
 xi 
 
 LXXI A. Copiapo. The Capella de Candelaria, an adobe chapel more than ioo years old, which has 
 survived repeated earthquakes. Its adobe walls are tied together by iron rods which go 
 through from side to side and are fastened with key plates. The tower is a very light 
 construction with wood frame. On right is a new church built in 1923, collapse of roof 
 
 of old chapel having rendered it unfit for service.Pocket 
 
 B. Copiapo. Plaza of Juan Godoy. Houses adjoining the plaza on both sides and the church 
 escaped serious damage to their external walls, but interior plastering was generally 
 destroyed. Foundation material is of gravel and construction of buildings is superior 
 to that of most houses in the city. Block of adobe houses on right was built after 
 earthquake of 1819, at a time when necessity for good workmanship was appre¬ 
 ciated .Pocket 
 
 LXXII A. Salaverre, Peru. A landing on northwest coast of Peru in lee of a small promontory. 
 
 This is a characteristic west coast port of South America, which is poor in harbors. 
 Steep rise of mountain is an effect of recent warping and faulting. Light-colored areas 
 
 are sand dunes which are here blown up to a height of 3,000 feet.Pocket 
 
 B. Copiapo. Panoramic view from bridge, comprising sweep from northeast to southwest 
 and showing marshy character of river bed. Wall along river bounds area that has 
 
 been filled in and on which maximum destruction occurred.Pocket 
 
 LXXIII. Geologic sketch map of Atacama, Chile.Pocket 
 
 LXXIV. Island of San Ambrosio; facsimile of chart prepared by the Covadonga Expedition, 
 
 1874 .Pocket 
 
 LXXV. Island of San Felix; facsimile of chart prepared by the Covadonga Expedition, 1874. .Pocket 
 
 TEXT-FIGURES 
 
 PAGE 
 
 Fig. 1. Diagram showing proportion of total destruction (black), serious damage (crossed), and slight dam¬ 
 age (white) in houses of tapiales (a), adobe bricks ( b ), frame with brush and adobe (c), and 
 
 frame buildings with Guayaquil cane ( d ). 23 
 
 2. Plan of house of Senor Melendez, illustrating effects of earthquake. 36 
 
 3. Atacama monument. Plan and elevation. 40 
 
 4. Diagram of tapiales, illustrating force required to overturn wall two blocks high considered as one 
 
 block . 48 
 
 5. Diagram of tapiales, illustrating force required to overthrow wall two blocks high when the blocks 
 
 moved independently . 48 
 
 6. Section of Plain of Coquimbo (Darwin). 104 
 
 7. Section through terraces at Coquimbo. 105 
 
 8. North-south section across valley of Coquimbo (Darwin). 106 
 
 9 Section of bluff at mouth of Quebrada Gulebron, Coquimbo. 107 
 
 10. Pliocene-Pleistocene(?) section, Quebrada Gulebron, Coquimbo. 109 
 
 11. Field sketch of thrust, Quebrada Paipote. 161 
 
 12. Field sketch of anticline, Quebrada Paipote. 162 
 
 13. Field sketch of thrust, Quebrada Paipote. 163 
 
 14. Field sketch of Cerro Guerin. 163 
 
 15. Field sketch of thrust in Cerro Ladrillos. 164 
 
 16. A and B. Field sketch of Cretaceous limestone and intrusive, section and plan; near Pabellon. 165 
 
 17. Field sketch of thrust near Hornitos. 165 
 
 18. Field sketch of bed and moraine of glacierette on Cerro de la Iglesia. 1 66 
 
 19. Field sketch of La Iglesia thrust. 166 
 
EARTHQUAKE CONDITIONS IN CHILE 
 
 INTRODUCTION 
 
 On November io, 1922, at about eleven forty-five p. m. there occurred an earth¬ 
 quake of very great energy, which literally shook the earth. The tremors which 
 radiated from it were registered in the Americas, Europe, Africa and Asia, wherever 
 there were instruments capable of recording them. In this respect it was not a very 
 unusual shock, there being annually a number of so-called world shakers. But it 
 happened violently to affect a district in central Chile where the conditions in the 
 cities were favorable to disaster and it occasioned, therefore, a catastrophe of notable 
 magnitude. 
 
 News of death, suffering, and need was flashed in the wake of the earthquake 
 waves to all peoples, and there was an immediate response to the call for help. A 
 large fund was raised to relieve destitution and to rehabilitate the communities. 
 At the same time the earthquake aroused scientific interest in the nature of the 
 phenomena and caused those who were engaged in seismological research to seek 
 the means to carry out an investigation on the spot. 
 
 The Seismological Society of America had previously investigated the activity 
 of several shocks that had occurred in California, but could not finance an expedition 
 to Chile. It appealed to the Carnegie Institution of Washington, which secured from 
 the Carnegie Corporation of New York a grant to defray the actual expenses of a 
 journey to and through the region of maximum effects, to investigate the scientific 
 and the practical human problems there presented. 
 
 Having been invited by Dr. John C. Merriam, President of the Carnegie Insti¬ 
 tution of Washington, to carry out these studies, the writer sailed from New York on 
 January 11, 1923, and returned to that port on September 2. Seven months were 
 spent in Chile, five of them in field work in the province of Atacama, where the earth¬ 
 quake had been most severe. 
 
 The conditions of travel were difficult. Atacama is a desert country. Hamlets 
 are few and are separated by long distances where there is neither shelter, food nor 
 water. The earthquake had destroyed some pueblos and had reduced others to great 
 need. The traveler could expect but little, however ready the hospitality of the people, 
 which indeed never failed him. Under these circumstances the results of the research 
 must have been comparatively meager, if the Chilean administration had not provided 
 facilities, which none but it could have furnished. The Government-owned railway 
 runs the length of the northern provinces, from south to north. Free passage was 
 given on it and a special car was placed at the service of the writer, who made it his 
 
 1 
 
2 
 
 Earthquake Conditions in Chile 
 
 base of operations. It was hauled some 4,000 kilometers and was always available 
 at the point to which he might wish to return from a more or less extended expedi¬ 
 tion off the railroad. 
 
 Furthermore, it was understood that a stranger could hardly hope to solve the 
 problems of the structural geology of the region satisfactorily without the assistance 
 of a geologist already familiar with the rocks and their relations. Dr. Johannes 
 Felsch, who had studied the geology of northern Chile during seven years as official 
 geologist assigned to the duty of locating water supplies for the railroad, was dele¬ 
 gated to accompany the writer and much of the result attained in the investigation 
 of the geologic faults was due to his intimate knowledge of the formations. 
 
 Again, when it became desirable to extend the observations to the volcanic islands 
 of San Felix and San Ambrosio, even at the cost of the voyage of 1,250 miles (2,000 
 km.) to and fro, the Minister of the Marine placed the corvette Aguila at the writer’s 
 disposal, under the command of Captain Hector Diaz. 
 
 To the President of Chile, Dr. Arturo Alessandri, the expedition became espe¬ 
 cially indebted for the liberal cooperation which he caused to be extended to its efforts. 
 He fully appreciated the significance of the scientific research as well as the purpose 
 of the more practical studies of those conditions that make earthquakes more or less 
 dangerous, and desired cordially to promote cooperation between Chilean scientists 
 and their American colleagues. Plis initiative in this respect had been anticipated by 
 Dr. Beltram Mathieu, Minister from Chile to Washington, who both officially and 
 personally did everything in his power to establish helpful relations between officers 
 of the Chilean Government and the representative of the Carnegie Institution. 
 
 In official circles in Santiago, Dr. Xavier Gandarillos Matta, Director of the 
 Bureau de Minas i Geologia, and his chief, Minister Francisco Marclones, were espe¬ 
 cially cordial in giving their personal support to the purposes of the expedition. The 
 Director General de Ferrocarriles Nacionales, Dr. Rudolfo Jaramillo, took a practical 
 interest in the investigation and provided the special car for the convenience of the 
 geologist, in return for which courtesy the latter made a report on the local condi¬ 
 tions that affected the earthquake hazard along the railroad. Don Carlos Silva 
 Vildosola, editor of El Mercurio, lent the aid of his great daily to the publication of 
 such current reports of the work of the expedition as were of general interest. 
 
 A great loss to the science of seismology and a grave disappointment in the coop¬ 
 eration anticipated in prosecuting the earthquake studies was occasioned by the 
 death of Dr. Le Comte Ferdinand Montessus de Ballore, head of the Servicio Sis- 
 mologico de Chile. He had known of the action taken by the Carnegie Institution and 
 had looked forward eagerly to the proposed joint scientific studies, but was stricken 
 unconscious on the day the writer left New York and died on the day of his arrival 
 at Valparaiso, January 31. He left no successor, either in Chile or in the world. His 
 lifelong devotion to the investigation of earthquakes, their activities, their geo¬ 
 graphic distribution and their relation to geologic conditions had made him pre¬ 
 eminently the master of the science. His assistant in Santiago, Dr. Carlos Bobilier, 
 did what lay in his power to carry out the wishes of his deceased chief. 
 
Introduction 
 
 3 
 
 In the provinces, Don Luis Romero, Intendente de la Provincia de Atacama, was 
 particularly helpful in securing data regarding the effects of the terremoto, and in 
 Don Luis Sierra Vera, the writer found a most capable associate and colleague. The 
 latter, a professor of natural history at the Lyceo de Copiapo, had long been a student 
 of earthquakes as they occur at Copiapo and furnished precise data regarding the 
 phases of the latest shock, which he had observed with extraordinary coolness while 
 the city was being all but destroyed. 
 
 To many friends and helpful acquaintances whose thoughtful attentions made 
 the journey a pleasure and a satisfaction to recall, the writer would extend his sin¬ 
 cere appreciation of their manifold courtesies and kindnesses. Especially to the 
 American Minister at Santiago, the Honorable Dr. William Miller Collier, and to 
 Sir John and Lady Murray at Vallenar his thanks are due. 
 
 The itinerary of the journeys in Chile comprised a number of distinct excur¬ 
 sions. Santiago, the center of official relations, was visited first and there contact 
 was established with the Chilean government. Copiapo, Coquimbo, La Serena and 
 Vallenar were visited and studied during the latter part of February, March, and 
 part of April. The latter part of April was spent at the Potrerillos mining camp as 
 the guest of the Andes Copper Mining Company, and great assistance was given the 
 writer in his observations in the higher Andes by officials of the company, especially 
 by Mr. James E. Harding, Geologist. Similar courtesies were extended at the 
 Chuquicamata camp of the same company, in May. In the interim, April 27 to May 6, 
 the voyage with Captain Diaz of the Aguila was made to the islands of San Felix and 
 San Ambrosio, sailing from and returning to Chanaral. After further studies at 
 Potrerillos and a visit to Chuquicamata the writer joined the party headed by 
 Dr. Juan Felsch, official geologist, and with him made extensive trips on horseback 
 with pack mules into the Cordillera east and southeast of Copiapo. Geologic sections 
 were examined in the Quebrada de Paipote, in the upper Copiapo valley to the head 
 of the Rio Manfias, on the Rio Huasco from its source to the Pacific, and also on the 
 Rio Elqui from Rivadavia to La Serena. Winter storms prevented more extended 
 trips in the high Andes, but the surveys reached all of the principal sections of the 
 Cordillera, including the Coast Range, the western slopes of the Andes, and the 
 plateaus and volcanoes at altitudes of 13,000 to 16,000 feet (4,000 to 5,000 meters). 
 
 The scientific results of the expedition may be summed up in the statement that 
 the geologic structure of the Cordillera was determined; the occurrence of earth¬ 
 quakes was traced to the active development of the range; and it was found that the 
 Andes constitute a live mountain chain which is being pushed upward and eastward 
 on a deep-seated and probably complex fault zone or system of overthrusts. The 
 practical studies of the destruction caused by the earthquake led to suggestions for 
 safer methods of building with the materials available in the country, and designs 
 of resistant buildings were published in a pamphlet entitled La Casa Segura contra 
 Terremotos, which was distributed by the Carnegie Institution of Washington to the 
 people of Chile in recognition of the cooperation they had extended to the expedition. 
 
 Stanford University, California, BAILEY Willis. 
 
 September 1926, 
 
0 
 
 LlK^ny 
 Of WE 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 A. Copiapo. General view of Copiapo basin and city. Area of greatest destruction lies in distant middle grour 
 (eastern) half of city, which is on slope of alluvial cone. Hills in right (western) half of panorama are Paleozc 
 Andes. Paipote at mouth of the Quebrada Paipote, where it joins the Copiapo valley, lies in extreme middle dista 
 
 B. Coast range between Pueblo Hundido and Chanaral. The dark rocks which form heights of distant hills are Paleozc 
 
 large dike of black diabase, probably also of Paleozoic age. The vie 
 
Plate I 
 
 3 right of church in center of picture. This is the area of marshy formations. There was less destruction in left 
 •ocks and belong to Coast Range. Those on left (east) are of Mesozoic rocks and constitute foothills of the 
 
 
 Mates and schists; light-colored masses are intrusive granite. High ridge in middle foreground show's outcrop of a 
 lustrates the characteristic structure of the Coast Range of Atacama. 
 
 mm 
 
toy 
 
 Oi /Mt‘ 
 
 JJNlVEl?,' , ■ .i • !',ig|g 
 
 
 
 
 
 
 
 
 
 
 
SECTION I 
 
 RELATING TO EARTHQUAKES, THEIR HISTORICAL 
 SEQUENCE AND EFFECTS IN ATACAMA 
 
REGIONAL DESCRIPTION OF ATACAMA 
 
 Chile is extraordinarily long and narrow. Her territory extends from Cape 
 Horn to the Bight of Arica; that is, from latitude 52 0 to latitude 18 0 , a distance of 
 2,400 miles (3,800 km.). Yet, clinging to the western slope of the Andes, her domain 
 is nowhere more than 200 miles (320 km.) across from east to west. 
 
 The country may be divided into three distinct sections. The southern, from 
 Cape Horn to latitude 41 °, resembles the southeastern coast of Alaska in being a 
 region of profoundly deep fiords margined by an archipelago of rocky islands. 
 Glaciers occupy the heights, and the land is inhospitable. The central section, which 
 is the heart of the country, extends from Puerto Montt in latitude 41 0 to Copiapo 
 near latitude 27 0 , nearly a thousand miles (1,600 km.). This zone corresponds very 
 closely with the State of California, being very similar not only in area and topog¬ 
 raphy but also in diversity of climate. Remembering that the two countries are on 
 opposite sides of the equator and that therefore north and south are reversed as re¬ 
 gards climatic conditions, we have in southern central Chile the heavy rainfall and 
 dense forests characteristic of northern California; whereas in northern central Chile 
 there is a semiarid region corresponding to the irrigated valleys about Los Angeles. 
 In the vicinity of Santiago, as in California, there is a longitudinal valley, west of 
 which is a coast range; and in each country there is on the east the great barrier of the 
 high Cordillera, which impedes intercourse with the interior of the continent. The 
 northern third of all Chile comprises the desert of Atacama and corresponds in climate 
 and topography with extreme southern California and the peninsula of Lower Cali¬ 
 fornia. It is a region of interior basins, of salt plains and sterile mountains—one of 
 the most utterly arid districts of the world. 
 
 The parallel with California fails when we try to compare the river systems. 
 For there is in Chile no such great longitudinal system as that of California. In the 
 latter State the rivers of the Sierra Nevada unite in the Sacramento and San Joaquin, 
 and these two, joining their waters, discharge into San Francisco Bay. In Chile, on 
 the contrary, all of the rivers flow separately from the Andes to the sea, and the 
 divides between them are in many places mountain ranges of considerable altitude. 
 This topographic condition has made it difficult to establish and maintain intercourse 
 between the northern and southern sections of the country. From Santiago south to 
 Puerto Montt, a distance of 400 miles (640 km.), the difficulties in the way of con¬ 
 struction of a railroad line were not serious, although it required skilful engineering to 
 locate a route with a reasonably good grade. Communication between Santiago and 
 Valparaiso on the coast is even easier. But from Valparaiso northward for a distance 
 of some 800 miles (1,300 km.) the topographic conditions render almost impossible the 
 successful commercial operation of the longitudinal railway. That railway alternately 
 
 7 
 
Earthquake Conditions in Chile 
 
 ascends and descends on grades which in places are so steep as to require rack and 
 pinion, and the capacity of locomotives is therefore limited to short trains. For miles 
 the road climbs among barren cliffs on the sides of waterless gulches, or winds across 
 gravel plains where the few growing plants in sight, the low clusters of desert shrubs, 
 may easily be counted as the train crawls past. The road would never have been built 
 except as a military necessity to bind the country together. Even though it is in 
 operation, the cities in the irrigated river valleys depend largely on the branch rail¬ 
 roads, which connect them with ports at the river mouths where the coasting steam¬ 
 ers frequently touch. 
 
 The terremoto of November io violently affected only this northern region, the 
 stretch of 400 miles (640 km.) between Coquimbo and Copiapo. In this area it shook 
 the barren mountains and plains, destroying the huts of goatherds, but in general 
 leaving no other trace. Only where the populations of little communities settled along 
 the rivers had built their clusters of adobe houses or had laid canals along the canyon 
 walls could the shock do any material damage to man and his works. It was thus 
 fortunately limited in its power to harm, but the conditions were unfavorable for any 
 detailed study of the extent and distribution of its intensity. 
 
 The first notices of disaster came from La Serena and Coquimbo. These two 
 towns are situated on Coquimbo Bay, in latitude 30°, at the mouth of the Rio Elqui. 
 Coquimbo is located on the rocky peninsula which forms the western side of the bay 
 of that name, while La Serena is built on the gravel terraces of the Rio Elqui. The 
 former is a commercial port consisting of the wharves and warehouses essential to 
 commerce and a single street, along which runs the railway. Above the latter the 
 residences are perched on the granite ledges of the promontory. There was also an 
 extension of the city over the beach and marsh lands at the southern end of the bay, 
 but that section was swept away by the earthquake wave. 
 
 La Serena is a city of gardens and orchards, girt about by high walls in the 
 Spanish style, and is the seat of government for Coquimbo Province. It is an old city 
 with records going back to the days of the conquistadors, and it has a long record 
 of earthquake experiences, as appears in the historical notes. 
 
 The valley of the Rio Elqui, a large stream for this region, is narrow and precip¬ 
 itously walled in. The railroad line, which follows it for about 50 miles (80 km.) above 
 La Serena, winds between the cliffs and the narrow cultivated bottom lands. Only 
 at one point, Vicuna, does the arable land spread out to a mile or more in width. Above 
 it rise the cliffs of dark-red volcanic rock, almost devoid of vegetation. At the end 
 of the railroad, at Rivadavia, the main river is formed by the junction of two streams 
 which come from the south and north. They head in many branches in the heights 
 of the Andes, among peaks which rise to 17,000 or 18,000 feet (5,000 to 5,500 meters), 
 and they have extremely rapid falls. 
 
 The earthquake was by no means impartial in its work in this valley. It did 
 little harm to Coquimbo, except by the wave which followed it. It shook La Serena 
 severely, damaging a great many buildings. It left Vicuna almost scatheless, but 
 practically destroyed Rivadavia, which lies farther east. This peculiar irregularity 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate II 
 
 A. Coquimbo. Looking north across district swept by earthquake wave. 
 
 B. Coquimbo. Looking south to low district, swept by earthquake wave. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate III 
 
 A. Coquimbo. Effects of earthquake wave in railroad yard; height of wave 26 feet (8 meters) 
 
 above mean tide. 
 
 B. Coquimbo. View from hill south of bay, looking northeast across flat swept by earthquake wave 
 

 
 
 LIBRARY 
 
 OF THE 
 
 UNIVERSITY OF ILLINOIS 
 
Regional Description of Atacama 
 
 9 
 
 of effect was chiefly due to the nature of the rock or ground on which the several 
 towns are built, but also to the occurrence of fault lines where the shock was most 
 violent, or where possibly secondary shocks originated. 
 
 In the generally straight coast line of Chile, Coquimbo Bay is one of a number 
 of small indentations which are incidental to a peculiar structure of the Coast range. 
 The range is not continuous, but is made up of many sections which lie at a slight 
 angle, trending north by east where the coast lies north and south. They therefore 
 lie en echelon with reference to one another; and at the southwestern end of each 
 section, where the ridges run into the sea, there is a bay like that of Coquimbo. This 
 peculiarity is due to the faults which define the blocks, as will be described later. 
 
 The idea of a continuous coast range carries with it the suggestion of a con¬ 
 tinuous longitudinal valley. But, as has just been stated, the Coast range is inter¬ 
 rupted and the so-called longitudinal valley is also divided into separate basins by 
 high spurs which project westward from the Andes, even to the coast itself. 
 
 These characteristics of the topography become apparent when we leave 
 Coquimbo and follow the railway north to Vallenar, the next town of importance, 
 about 240 miles (150 km.) distant as the crow flies. Skirting Coquimbo Bay, the 
 line passes through La Serena and thence up the canyon of a small tributary of 
 the Elqui to a divide about a thousand meters above sea-level. It then descends 
 abruptly to the gorge of the Rio Choros, a small foothill stream of the Andes, climbs 
 again up a very steep grade to an altitude of 3,300 feet (1,100 meters), and, after 
 winding for some miles over the plateau which is a spur of the high Andes, descends 
 over a wide gravel plain to Vallenar, in the valley of the Rio Huasco. 
 
 In this stretch of 240miles (150 km.) there is no village of any consequence. The 
 railroad stations consist of a station house and water tank. From them mule trails, 
 not roads, lead off into the mountains, where there are numerous mining camps. Many 
 of the mines are superficially worked out and the miners have left. The region is 
 arid, but it is not salt-covered and utterly waterless, as are the nitrate basins farther 
 north. 
 
 Approaching the valley of the Huasco, one sees only the wide gravel plains 
 which extend beyond the view north and south and from the foothills of the Andes 
 on the east to the ridges of the coast range on the west. The width of the basin is 
 3 to 12 miles (5 to 20 km.) across the gravel plain. The river lies 600 feet (200 
 meters) below, sunk in the channel which it has cut across the longitudinal valley and 
 out through the coast range. It is a delightful surprise on arriving at the edge of the 
 trench to look down upon the orchards and gardens of the city of Vallenar. The river 
 bottom is but a quarter of a mile wide, but is a strip of rich verdure, being grown 
 with rank grasses in its marshy sections or planted and irrigated wherever it can be 
 protected from flood (Plate LXIX (in pocket)). 
 
 From the high gravel plain 600 feet (200 meters) above the river, one steps 
 down over three very distinctly marked terraces to the valley bottom. Each of these 
 terraces carries a large irrigation canal, which brings water from 10 to 30 miles 
 (16 to 48 km.) up the river and supports a rich growth of alfalfa. 
 
10 
 
 Earthquake Conditions in Chile 
 
 Behind the traveler is a parched, stony plain, but before him is a garden. 
 
 Vallenar was an Indian settlement before the Spaniards came, and has always 
 been an important cross-roads at which the east-west traffic down the valley of the 
 Huasco met the north-south lines of communication. Today it is the junction point 
 of the longitudinal railway with the branch line to the port of Huasco on the bay of 
 that name. The town is built on the gravel cone at the foot of a small ravine that 
 enters the river from the northeast, the site being determined by the fact that the 
 gravels heaped up by the little tributary constitute a foundation which has good 
 drainage and is higher than the marsh land of the river bottom. 
 
 The valley of the Huasco is a fertile zone stretched across sterile hills and plains, 
 and it is occupied by settlements and ranches for some 75 miles (120 km.) from its 
 mouth to the principal forks of the stream above La Pampa, where it has an elevation 
 of nearly 5,000 feet (1,500 meters). Throughout this stretch the little villages and the 
 ranch-houses were generally severely shaken by the earthquake. Vallenar suffered 
 most because it was much the largest town, but the intensity of the shock was simi¬ 
 larly effective in all other places whose foundations and geological relations were the 
 same. There were some curious instances of immunity, which again are to be ex¬ 
 plained by local geologic conditions. 
 
 We may here cite some of the principal facts. The town of Huasco, which, like 
 Coquimbo, is built on a granite promontory, shivered in the earthquake, but was not 
 shaken down. Huasco Bajo, a village 4 miles (6 km.) distant, built on alluvium and 
 near the line of a fault, was practically leveled. Freirina, a village 7.5 miles (12 km.) 
 farther up the valley, was very seriously damaged. It also is built on alluvium and 
 on the line of a fault. Vallenar, 23 miles (35 km.) from Freirina, located between 
 two faults, suffered most severely, but the damage done depended largely on the 
 original construction and the actual condition of individual houses and on the nature 
 of the ground on which they were built. In the gorge of the river east of Vallenar the 
 gravel terraces are very narrow or entirely wanting, and the rocks are near or at the 
 surface. The distribution of earthquake damage depends upon these conditions, it 
 being least where the foundation is rock. But the intensity was even more definitely 
 concentrated at those points where the gorge is crossed by thrust faults. Thus, on a 
 fault 2 miles (3 km.) west of Vallenar, in the Quebrada Valparaiso, movement was 
 renewed on an ancient landslide (Plates XXIII to XXVI). At the Quebrada Jil- 
 guero, 3 miles (5 km.) east of Vallenar, the cliff adjacent to the outlet of the stream 
 into the gorge of the Huasco was cracked for a height of 150 feet (50 meters) (Plate 
 XXII). The quebrada is located on a fault. Furthermore, in the little village of 
 El Transito, built on the alluvial cone of a tributary ravine, which in turn is deter¬ 
 mined by a thrust fault, there were few houses that survived the shock and the church 
 was ruined. 
 
 Extending northward from the valley of the Rio Huasco to that of the Rio 
 Copiapo, a distance of 100 miles (150 km.), the gravel plain that begins south of the 
 Huasco is continuous. It widens out and ramifies among the foothills of the Andes 
 and the spurs of the coast range, thus forming one of the major basins characteristic 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate IV 
 
 A. Near Coquiinbo. Hut, on coast 16 miles (25 km.) south of city, not damaged by earthquake, 
 
 showing weakness of shock at this point. 
 
 B. Coquimbo. Jointed Paleozoic granite near northern end of promontory. 
 

Regional Description of Atacama 
 
 11 
 
 of the series of depressions which lies east of the coast range in northern Chile. The 
 Rio Copiapo enters this basin from the southeast through a narrow gap in the granite 
 foothills and pursues its course in a wide flat valley westward to the coast. Just 
 upstream from the gap the valley of the Copiapo spreads out in an intermontane basin 
 some 3 km. wide and io km. long, which is a fertile oasis. (Plate I A.) 
 
 From time immemorial the oasis has been a center of population. It is the last 
 fertile spot on the route of travelers going northward into the utterly desert waste of 
 Atacama, and it is the first settlement at which the traveler from the desert may 
 refresh himself. It is also the center of what was an exceedingly rich mining region. 
 It is now the capital of the province and one of the most important towns in northern 
 Chile. 
 
 The present town of Copiapo is built on the eastern side of the oasis, partly on 
 the marsh land and made ground next the river and partly on the lower slopes of an 
 alluvial cone which descends abruptly from the neighboring heights. Since every 
 one desires flowing water for gardens, trees and drains, the upper limit of building 
 is fixed by the very moderate altitude to which water can be carried. The city, there¬ 
 fore, stretches its length between the river and this upper contour, and is long and 
 narrow. At the northern, lower end it extends into the gap beyond the alluvial plain; 
 southward it spreads over the valley, running out into farms and adjoining the older 
 Indian pueblo of San Fernando. The construction of the houses varies greatly, from 
 huts of wattled twigs and mud to massive walls of adobe or framed structures cov¬ 
 ered with stucco. These resisted the earthquake quite unequally, the adobe being the 
 weakest because of its excessive weight and little strength. There were, however, 
 very few houses which were not seriously damaged in the interior, even though the 
 outer walls appeared not to have suffered much; and in a large proportion of cases 
 the collapse of the heavy roofs rendered the houses uninhabitable. 
 
 As might be expected, the destruction was greatest on the marshy ground near 
 the river; it was less on the slope of the alluvial cone—indeed, relatively insignificant 
 in the upper part of the city—and it was also comparatively slight in the northern 
 end in the gap where the rocky spurs close in upon the valley. Thus the destructive¬ 
 ness of the earthquake at Copiapo was directly related to the character of the subsoil. 
 
 La Serena, Vallenar, and Copiapo are three important towns which lie almost 
 in a straight line that trends north-northeast from the first named, along the inner 
 side of the coast range. It was natural to infer, as I at first did, that they were located 
 along a single great fault line similar to the San Andreas fault of California. This 
 afterwards was found not to be the case. There are many faults instead of one, and 
 no one of them has the distinction of having caused the wreck of more than a single 
 town. Copiapo, indeed, is not situated on any fault line. There is one which passes 
 about 6 miles (io km.) southeast and another about 2^4 miles (4 km.) west of it, but 
 its unfortunate reputation for being a place of special and peculiarly violent earth¬ 
 quake activity rests rather upon the marshy character of its subsoil than upon any 
 other condition. It is somewhat surprising, where all the region round about is utterly 
 sterile, to find vegetation growing so rankly that it will produce thick beds of peat. 
 But peat occurs in the valley of the Copiapo River near Monte Amargo, some 40 km. 
 
12 
 
 Earthquake Conditions in Chile 
 
 below Copiapo (Plate L), and peat probably underlies the sands of the plain upon 
 which San Fernando and the lower parts of the city of Copiapo are built. Water is 
 very abundant in this intermontane basin. The latitude, 27 0 south of the equator, cor¬ 
 responds with that of the Gulf coast of Texas, but the sun is even hotter than in Texas, 
 because the dry atmosphere of the desert allows the rays to pass undiminished in in¬ 
 tensity. Thus, marsh vegetation grows rankly the year around. Its roots and decay¬ 
 ing stems form a spongy mat which thickens year after year until, by some accident of 
 flood, the vegetation is buried under sand and the sparser grasses of the plain replace 
 the marsh. The conditions for this kind of growth are extremely favorable above the 
 obstructed outlet of the intermontane basin, and render it most probable that the 
 unstable condition of the foundations of the city is due to the existence of a bed of 
 peat, which is, however, buried beyond the depth of any of the shallow wells in the 
 plain. The remedy, of course, is to grade the slope of the alluvial cone above the pres¬ 
 ent city, provide water for irrigation at higher levels, and condemn the residences on 
 the low ground. If buildings must be erected on the unstable soil they should be so 
 constructed as to resist its vibrations in any earthquake. 
 
 The longitudinal basin which extends from Vallenar to Copiapo ends immedi¬ 
 ately north of the latter city, where again a high spur of the Andes projects west¬ 
 ward. The railway climbs to the pass of Chimbero, at an altitude of nearly 6,600 feet 
 (2,000 meters), and then descends into the southernmost of the broader and more 
 arid basins of the true desert. Pueblo Hundido is the station situated at the south¬ 
 western end of this basin, in the channel of the Rio Salado, a stream whose waters do 
 not suffice to flow beyond the foothills of the Andes, but whose valley is nevertheless 
 cut through to the coast at the bay of Chanaral.- 
 
 Pueblo Hundido and Chanaral, 63 miles (100 km.) north of Copiapo, are the 
 first settlements of sufficient importance to have given any record of the intensity of 
 the earthquake. But neither of them suffered materially from the shock. Chanaral 
 indeed was struck by the earthquake wave, but was not damaged by the temblor itself. 
 Both places appear to lie to the west of the trend of the fault zone in which the activity 
 was pronounced. But going eastward from Pueblo Hundido up the Rio Salado, we 
 come in 47 miles (75 km.) to the copper-mining camp of Potrerillos, at an altitude of 
 10,400 feet (3,100 meters), and here the buildings were damaged to the extent of 
 some $75,000. They were mostly long, low structures built of a specially good adobe 
 and strengthened by a continuous band of reinforced concrete above the doors and 
 windows. They were, nevertheless, seriously damaged by cracks. Had they been of 
 the usual type of native adobe they would probably have been completely ruined. 
 There is no question, therefore, that the earthquake was almost if not quite as violent 
 at this great altitude among the rocky peaks of the Andes as it was in the lower 
 valleys. 
 
 Potrerillos is located on a group of thrust faults, which may be seen in the neigh¬ 
 boring canyon but which, beneath the mining camp itself, are buried by the gravel 
 wash of an ancient valley. This gravel is thoroughly drained by a canyon 1,500 feet 
 (450 meters) deep and, being full of air-spaces, might have been expected to absorb 
 the earthquake vibrations. It is, however, fairly old (Pliocene or early Quaternary) 
 
UNWffts. 
 
 UF&ARY 
 Of THE 
 
 lTY 0F ILLINOIS 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate V 
 
 A. Vallenar. Water forced out of river bed by shaking down of alluvium. 
 
 B. Vallenar. Two-story frame and adobe bouse standing among ruins of one-story 
 
 massive adobe houses. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate VI 
 
 A. Copiapo. Typical adobe ruin. 
 
 B. Copiapo. Good adobe ruined by heavy mud roof. 
 
LIBRARY 
 OF THE 
 
 UNIVERSITY OF ILLINOIS 
 
Regional Description of Atacama 
 
 13 
 
 and has undoubtedly been consolidated by a great many earthquakes. It evidently 
 transmitted the shock effectively (Plate XLVI). 
 
 We have thus described the district in which the terremoto of November io was 
 of destructive violence. It extends from La Serena on the coast, north by east to 
 Potrerillos at an altitude of more than 10,000 feet (3,000 meters). It is a zone of 
 thrust faults, 14 of which are known to extend nearly parallel to one another at dis¬ 
 tances apart that vary from 2*4 to 12 miles (5 to 20 km.). The total width of the 
 faulted zone in the latitude of Copiapo is about 100 miles (150 km.), but these are not 
 its limits. The ocean prevents us from arriving at anything more than a surmise as 
 to the extension of the zone westward, and the winter season prevented the writer 
 from exploring eastward in the high plateau of the Andes or across to the eastern 
 slope of the Cordillera, where faults of a similar character are reliably reported to 
 exist. 
 
 The length of the zone of maximum activity of the earthquake, from La Serena 
 to Potrerillos, is 300 miles (500 km.). Here again, however, we are obliged to admit 
 that the effect may have been violent beyond these limits; for south of La Serena the 
 fault zone runs into the ocean, and north of Potrerillos are uninhabited salt plains and 
 barren ranges varying in altitude from 12,500 to 17,000 (4,000 to 5,000 meters). If 
 we attempt to draw an inference from the distribution of intensity, we find but little 
 reason to limit the area of great violence by the known facts. The shock was no doubt 
 less at La Serena and more violent at Vallenar and Copiapo. It may have been some¬ 
 what less at Potrerillos, but not enough to indicate that it was rapidly diminishing in 
 intensity toward the northeast. Thus the area of severe vibration was large. The dis¬ 
 turbance was nevertheless not violent, in general. Local conditions, especially the 
 proximity of fault planes and the weakness of alluvial deposits, determined the areas 
 of destructive violence, where the poor structures built by man were thrown down 
 and he was buried in the ruins of his own handiwork. 
 
 History repeats itself where it depends on permanent natural conditions. 
 La Serena, Vallenar and Copiapo have again and again been the centers of maximum 
 damage by earthquakes in southern Atacama. The nature of the alluvial ground 
 which makes earthquakes dangerous is the attraction that draws man to the spot, 
 for there he can irrigate the land, raise fruit and alfalfa, and establish his home in an 
 oasis. These advantages have overcome the fear of the terremoto. Rather than aban¬ 
 don their homes, the dwellers in these cities have returned each time to the ruins and 
 have rebuilt on the old site; sometimes they took warning and built better structures, 
 but as a rule the old ways prevailed and there has been but little change in the archi¬ 
 tectural types during 400 years. In 1922 proposals were made, as they had been made 
 before, to move Vallenar to some neighboring, supposedly safer position. They were 
 argued with earnest, even with heated purpose, but the arguments were based largely 
 on self-interest. In the end, the general economic control prevailed, invested interests 
 refused to be uprooted, and a new Vallenar was erected where the old houses had 
 stood. It was so also in Copiapo and elsewhere. And few considered the saying of 
 the Jesuit father who in 1665 wrote: “ He who inhabits a house of adobe lives in his 
 tomb.” 
 
EARTHQUAKE HISTORY OF ATACAMA 
 
 LIST OF SEVERE EARTHQUAKES, 1543 TO 1922 ^ INCLUSIVE 
 
 1543. Tarapaca. 
 
 1604. December, La Serena, 
 
 Before 1648. Coquimbo. 
 
 I 73°. July 8, La Serena. 
 
 1792. November 30, La Serena. 
 
 1796. March 30, Copiapo, Vallenar, and Huasco. 
 
 1796. August 24, Copiapo. 
 
 1801. January 1, La Serena. 
 
 1819. April 3, 4 and 11, Copiapo. 
 
 1822. November 5, Copiapo and Coquimbo. 
 
 1843. December 17, La Serena. 
 
 1847. January 19, Copiapo. 
 
 1847. October 8, Coquimbo. 
 
 1849. December 17, Coquimbo. 
 
 1857. November 7, Copiapo. 
 
 1859. October 5, Copiapo. 
 
 1864. January 12, Copiapo. 
 
 1877. July 26, Coquimbo, Chimbo, and Tamaya. 
 
 1877. August 29, Vallenar. 
 
 1903. December 3, Vallenar. 
 
 1903. March 19, Vallenar. 
 
 1918. December 4, Copiapo. 
 
 1922. November 10, Copiapo, Vallenar, Huasco, and Coquimbo. 
 
 Thus the records of 400 years list 22 severe earthquakes in Atacama, distributed 
 through a zone from Coquimbo and La Serena in the south to Copiapo in the north. 
 The center of greatest effect is indicated by the name of the place, in each case, but 
 none of these severe shocks was of local occurrence only. Their extent may be indi¬ 
 cated with more or less accuracy, according to the completeness of the available data, 
 in the following descriptions, which also indicate the severity of the shock in the 
 place of greatest intensity. The notes are translated from the work of Count Fer¬ 
 nando de Montessus de Ballore, cited above. 
 
 DESCRIPTIONS OF TERREMOTOS, 1543-1918 INCLUSIVE 
 
 1543. Tarapaca —A severe earthquake, which prevented the Indians from showing the Com¬ 
 missioner, Lucas Martinez Begazo, the founder of Arequipa, the Mine of the Sun, of pure silver, 
 which they had previously worked. (Tarapaca lies some 200 miles north of Atacama, but not beyond 
 the region simultaneously affected by extensive shocks occurring in the latter province.) This earth¬ 
 quake is therefore here noted, as it is the earliest definitely recorded and may have extended to 
 Copiapo and other parts of the territory under discussion. 
 
 1604, December. La Serena —Concha relates: “This earthquake occurred in December 1604. 
 There is no account of the event whatever, except some slight references in certain public documents, 
 from which one may infer that it ruined a large part of the buildings of the city, which indeed were 
 few in number.” Thus: 
 
 “Record of the Cabildo de la Serena of July 17, 1605. The said church (the Metropolitan Church) is being 
 built and it having occurred when the walls were high that the earthquake, which there was in this city six months 
 
 1 Historia Sismica de los Andes Meridionales por Fernando de Montessus de Ballore, Director del Servicio 
 Sismolojico de Chile, Segunda Parte, 1912. 
 
 14 
 
Earthquake History of Atacama 
 
 IS 
 
 past, ruined the walls of said church, and it having been expedient to tear it down and rebuild it on account of the 
 one-third part which, by order of H. M., is provided from his funds, it was agreed to pay to Captain Juan de Bal- 
 dovinos de Leide one hundred pesos from the two-ninths pertaining to H. M., from the tithes of this year, and from 
 those to be received until he shall have been paid the one hundred pesos, and the said Captain Juan de Baldovinos 
 has built the said church, repairing the damage referred to, and has finished it to the height which the walls must 
 have, and he has petitioned that he be paid the amount of the said account.” 
 
 Before .1648. Coquimbo —This earthquake is recorded in the following from Bishop Villa- 
 roel. No other author has mentioned it. (Gobierno eclesiastico . . . . , Part II, Quest. XIII, 
 Art. Ill, 17.) 
 
 “ With reference to the earthquakes, processions have been very important: prodigious effects have been 
 observed. I will refer only to one (446. Oriente), not because it is unknown, but rather because it can not be for¬ 
 gotten; and because as I have been instructed in Lima, where it quakes, and in this my Bishopric an earthquake 
 destroyed completely the city of Coquimbo, I describe the instance in order that those who suffer from earthquakes 
 may know the remedy.” 
 
 In another passage Villaroel (p. 587) says that he had to rewrite his work in August 1648. The 
 earthquake must consequently have occurred before that year. 
 
 1740, July 8 —The great earthquake of July 8, 1730, devastated all central Chile (that is to say, 
 the region of which Santiago is the center and which lies far south of Atacama), but although its 
 area of destruction extended to La Serena, the damages, even though they were notable, were not of 
 such importance as is supposed by some historians or authors, as, for example, by Francisco Solano 
 Asta Buruaga y Cienfuegos in his Geographical Dictionary of Chile. This, therefore, is not the place 
 to describe this great seismic phenomenon. (See Hist, de los Andes mcridionales, Part IV, p. 75.) 
 
 77pp. November go. La Serena —Concha relates : There was another earthquake no less strong 
 (than that of December 1604) which also destroyed some buildings; but its havoc was by far not to 
 be compared with the other. 1 
 
 1796, March go, VI, 3/4. Copiapo and La Serena —A violent earthquake (says Sayago 2 ) 
 which did damage in the city of Copiapo, ruining the metropolitan or parish church, de la Merced. 
 
 the jail, and a great number of houses. Sayago appears to have known and to have abridged 
 
 an account in an administrative report, belonging to the archives of the Ministerio del Interior, pre¬ 
 served in the Biblioteca Nacional (vol. 656, No. 7721). It treats chiefly of estimates of the costs 
 in order that the Government may supply the funds necessary for the reconstruction of the princi¬ 
 pal edifices. It appears from these documents that the tower and facade of the parochial church 
 fell, but without personal injuries, and also it is indicated that Huasco and Coquimbo suffered in a 
 manner similar to Copiapo, but nothing is said of La Serena, which was likewise ruined, as is shown 
 by the statement which follows. 
 
 With reference to the earthquake in La Serena, Montessus quotes from J. T. Medina, Cosas 
 de la Colonia. 3 
 
 “ On the 30th of March, 1796, at 6 3/4 in the morning, this city suffered from a very violent movement of 
 the earth, which lasted at least 4 minutes in the first shock and was continued in others, but not as severe, for 
 more than an hour. The damages have been very considerable, chiefly in the churches. The Church of San Fran¬ 
 cisco was partly thrown down and the tower remained in such a ruined condition that it was necessary to tear it 
 down to avoid further injuries. The Metropolitan church lost its tiles and some adobe blocks (tapias) which had 
 fenced the cemetery. Deaths from the falling of houses were only three in number, and among them was the twelve- 
 year-old daughter of the alcalde, Don Francisco Soza. Many were dangerously wounded.” 
 
 The Church of Paitanaz, now Vallenar, built at the beginning of the eighteenth century, was 
 thrown down and was rebuilt in the same year. 4 
 
 Letter of the Cura, Juan Nicolas Varas y Marin, to the Bishop Maran, dated La Serena: 
 
 “ The earthquake was most severe in the districts of Coquimbo, Huasco, and Copiapo.” 
 
 1796, August 24, between X and XII. Copiapo — 
 
 “ Panic stricken by three consecutive movements of the earth of greater duration, though not of equal force 
 and violence, with that of March, which completed the ruin of the little that might survive such violent disturbances, 
 including what happened the first time, the people endeavored to fly to the hills, telling each other to their greatei 
 
 1 Cronica de la Serena, from its foundation down to our time, 1540-1870. Written according to the data taken 
 from the Archivos de la Municipalidad, Intendencia, and other papers. La Serena, 1870. 
 
 2 Historia de Copiapo, Copiapo, 1874. . . 
 
 3 Apuntes, Cronicas del Siglo XVIII en Chile, Segunda serie. Santiago, 1910, p. H 7 - 
 
 4 Memoria presented by the Cura and Vicario de Vallenar, Don Manuel Garcia, to the Bishop of La Serena, 
 Don Jose Manuel Orrego, on the occasion of the visit which he made him on June I, 1872. \ alparaiso, 1872. 
 
16 
 
 Earthquake Conditions in Chile 
 
 distress and fear a vague tradition to the effect that this city must be transformed into a lake by means of an earth¬ 
 quake, because it is situated in a meadow.” (Letter of the sub-delegate, Jose Ignacio Balbontin, of September 24, 
 1796, forming part of the various administrative papers which constitute the report on the results of the earth¬ 
 quake of March 30, in the district of Copiapo. Documents of the Ministerio del Interior, Biblioteca Nacional, 
 Vol. 656, No. 7721.) 
 
 1S01, January 1. La Serena —Concha. Cronica de La Serena, page 208, says: “A very severe 
 earthquake was experienced, January 1, 1801, which caused some damage.” 
 
 (He quotes a letter from the subdelegate Joaquin del Pino, who writes only of 
 the aid to be extended to the sufferers from the earthquake.) 
 
 18ip, April 3, 4 and 11. Copiapo —Earthquake and earthquake wave. It would seem that this 
 earthquake was the fourth to ruin the city of Copiapo, which was officially founded in 1744. for it 
 is known that various edifices, particularly the church of La Merced, had already been rebuilt three 
 times when the earthquake of 1819 occurred. The most extended account that it has been possible 
 to secure is that compiled by Don Diego Barros Arana in his well-known Historia Jeneral de Chile 
 (XII, 372). He, according to his statement, utilized the scanty data to be obtained from the few 
 periodicals of that time in addition to two reports which were sent to the Government of the United 
 Provinces of the Rio de la Plata by its diplomatic agent, Don Tomas Guidon. 
 
 This seismic phenomenon was characterized by a peculiarity which is sufficiently rare in gen¬ 
 eral, and which, up to that date, had never been observed in Chile, so far as we know: In an interval 
 of eight days, from the 3d to the nth of April, three distinct shocks assumed a destructive charac¬ 
 ter, each one of them causing notable damage. 
 
 Without any previous indication, at 10 o’clock on the 3d, an initial strong shock was felt 
 throughout the entire region, which threw the people into great alarm because of the very numerous, 
 consecutive, and repeated after-shocks that followed it, even though they were not so severe. 
 According to Sayago, many houses and walls of adobe blocks (tapias) were thrown to the ground 
 and the inhabitants, praying for mercy, fled to the parks, streets and patios. 
 
 On the following day, a little before dawn, at 5 o’clock, according to Barros Arana, or at 16 
 according to Sayago, another much stronger earthquake augmented the disaster, increasing the piles 
 of debris and adding to the terror of the inhabitants. Two years later the celebrated English traveler, 
 Captain Basil Hall, visited the region and gathered interesting details, which were still fresh in the 
 memories of the sufferers but do not occur in other documents. According to his account, it was then 
 that the church of La Merced of Copiapo fell, but without causing any deaths because some self- 
 possessed person induced the people to leave the church quickly, under the pretext of carrying the 
 sacred images outside in order to worship them there and implore the aid of heaven. This statement 
 is not without interest, since it gives occasion to think that the hour indicated by Sayago, 4 p. m., is 
 more probably correct than that given by Barros Arana, 5 a. m., it scarcely being probable that there 
 would have been many worshipers in the church at so early an hour. 
 
 According to the version of various witnesses this earthquake lasted about 4 minutes and was 
 accompanied by a terrifying noise. It threw down many houses in the cities, in the suburbs, and in 
 the surrounding country. In Copiapo the most notable was the destruction of the two churches, 
 La Matriz and La Merced, and about one-half of the houses. The jail and the municipal residence 
 were ready to fall down. Of La Merced there remained erect a part of the side-walls and of the 
 facade, but even they were shaken and badly cracked. The great buttress walls were thrown down, 
 with the exception of one, the upper part of which was separated by 3 or 4 feet from the wall which 
 it was built to sustain. 
 
 Two years later Basil Hall was able to observe in the neighboring orchards that cypresses had 
 been thrown down upon the ruins, while many other trees remained more or less in a leaning posi¬ 
 tion. He says that here and there one could still recognize wide cracks opened in the ground, which 
 had not been closed, in spite of the long time that had elapsed since the earthquake. He noted that 
 the precinct of La Chimba had suffered comparatively little. 
 
 Terrified by these occurrences and kept in constant alarm by the after-shocks, which did not 
 diminish in intensity and frequency, the people who had fled without shelter or resources to the 
 slopes of the adjoining hills of Chanchoquin and Rosario had not dared to return to their ruined 
 homes; and this was indeed fortunate, since, on the nth, at n of the morning, according to Sayago, 
 or in the night as stated by Barros Arana, a much more violent earthquake completed the ruin. An 
 hour and a half later there occurred still another shock, which was almost as strong and extremely 
 prolonged, lasting, according to the testimony of those who experienced it, some 5 or 6 minutes. 
 
Earthquake History of Atacama 
 
 17 
 
 Except for the church of La Merced, the accounts do not distinguish any of the principal edi¬ 
 fices, as to whether they were damaged initially by the earthquake of the 4th or by that of the nth. 
 Be that as it may, we are also ignorant of the extent of the area damaged; but it is certain that the 
 church of Matriz de Paitanaz, which was on the present site of Vallenar, was also ruined. 
 
 There occurred an earthquake wave, and in regard to it Diego Barros Arana says: 
 
 “Along the coast, where the earthquake was intense, it was observed that the sea retreated upon itself, but 
 shortly advanced over the land, reaching in some points a distance of more than 600 meters beyond the line of 
 the highest tides. This extraordinary movement of the waters of the ocean was noted at other points along the 
 coast to as much as 200 leagues from those localities.” 
 
 Without giving any more explicit details, the illustrious historian cites the testimony of the 
 commandant of the naval vessel La Fortunata, which, having been anchored off the dock of La Nueva 
 Bilbao, now called Constitucion, was wrecked upon the rocks in consequence of the advance and 
 retreat of the sea, after having broken away from her anchors. The accident occurred on the 12th at 
 2 o’clock in the morning. 
 
 Now, we know from other earthquake waves which have occurred on the coasts of Chile, 
 especially from those of August 13, 1868, and May 9, 1877, that earthquake waves advance from 
 north to south with a velocity of about 300 marine miles per hour. Hence we may directly infer that 
 the third earthquake of Copiapo occurred at 11 p. m. and not in the morning of the nth, in order 
 that it should agree with the hour of the earthquake wave in Constitucion. 
 
 The same phenomenon was noted in Caldera, as was natural, and Peter Schmidtmeyer relates 
 that they later recovered ingots of copper which the advance of the sea had buried beneath great 
 masses of sand. No other observations relating to the earthquake wave are known, and we are 
 equally ignorant regarding the duration of the after-shocks of the earthquake. 
 
 At this period the public edifices of Copiapo were built of very heavy walls of masonry—it 
 might be of stone or of brick—while the private houses were constructed of adobe with frames of 
 wood, the uprights or joists of which were set deep in the earth. They resisted much better, and the 
 inhabitants, taught by the experience of the earthquake of 1819, according to the testimony of the 
 oldest inhabitants of the city, from that time on adopted the system of construction now in use; that 
 is to say, to build with frames of wood, mud, and Guayaquil cane, a method which without doubt 
 has for almost a century saved the city of Copiapo from various disasters which it could not other¬ 
 wise have escaped as a consequence of the numerous violent earthquakes which have since that time 
 shaken its unstable foundations. As a matter of fact, there has been no other real catastrophe since 
 1819. 
 
 This earthquake occasioned great demonstrations of charity in Huasco, and especially in San¬ 
 tiago, where public subscriptions facilitated giving relief to the sufferers of Copiapo in the form of 
 money, clothing and provisions. 
 
 It was proposed to move the city of Copiapo to a safer locality, but this project was not carried 
 out. In regard to it Sayago says: 
 
 “ After several days, during which the oscillations of the earth ceased, the people recovered their poise and 
 little by little began to return to the city to undertake in some measure to restore the ruins; it was then that the 
 Lieutenant-Governor called together the councilmen, the cura and prelates, and the principal men in the neighbor¬ 
 hood, and constituted an open council in the suburb of Hidalgo, situated in front of the now abandoned powder 
 magazine at the foot of the slopes of Chanchoquin. 
 
 “ The assembly was called to consider the selection of a better site for the city and the problem of rebuild¬ 
 ing it. Many voices were raised to petition that it should be moved to some other place, where the ground might 
 be firmer, it being argued that, since the founding of the city in 1774, the church of La Merced and many other 
 public and private buildings had been three times rebuilt. Attention was called, however, to the fact that such a 
 proposal must be decided by the supreme government, and the Lieutenant-Governor was charged with the duty of 
 presenting the matter to Santiago. 
 
 “ General O’Higgins replied that there was no one who could better determine the question than the Council 
 of the city and neighborhood. 
 
 “ To this end, on the 20th of July, there was held a second open Council in the Chapter Hall, which had 
 already been repaired. Ten votes were cast to remove the city to Potrero Seco, 16 to Nantoco, 26 to Bodega, and 
 27 to remain on the same site. Thereupon the inhabitants began to remove the ruins and rebuild their dwellings and 
 fences, and the Council and the Lieutenant-Governor to dictate the necessary measures. Little by little the idea of 
 moving the city was abandoned.” 
 
 1822, November 4. Copiapo —Violent shock. Many houses damaged. 20-5 Copiapo. The city 
 was almost completely destroyed, and Coquimbo also suffered greatly. 1 Without any doubt, what- 
 
 1 Mallet, cita Quart. Journ. Roy. Inst., XVII, 39; Perrey, Nouv. Ann. des Voy. XXV, Fevr. 1825, 155; and 
 Darwin, Trans. Geol. Soc., V, 612, according to Journ. of Sci., XVII. 
 
18 
 
 Earthquake Conditions in Chile 
 
 ever, the phenomenon has been greatly exaggerated in all that relates to its effects, and it is probable 
 that the descriptions relate to the damage done by the earthquake of the 22d of November to old 
 walls and tumble-down houses. 
 
 1843, December 17, XVII, 10 or XVIII, 15. La Serena —An earthquake of notable force. A 
 pile of stone fragments, gathered from the ruins at the church of La Matriz to build the actual cathe¬ 
 dral, which lay in the center of the plaza where at the present time, 1870, the fountain stands, was 
 completely thrown down almost to the level of the earth; and many houses suffered considerable 
 damage. 1 
 
 1843, January 19, X, 50. Copiapo —This earthquake was the strongest that has been felt since 
 1822. Up to XIV o’clock (2 p. m.) at least 14 shocks were counted. Many houses collapsed and 
 many more suffered such damage that it was believed for the moment that the city would be com¬ 
 pletely destroyed. The shocks continued during three consecutive days. 
 
 1843, October 8, about XI. Coquimbo —Very little is known in regard to this occurrence, to 
 which reference is made by Goll, and it is probable that its effects have been exaggerated. It was felt 
 in Melipilla, Santiago, Valparaiso, and Copiapo. In Valparaiso the bells were rung. Damage is said 
 to have been done in Coquimbo and the neighboring towns in the interior. 
 
 T849, December 17. Coquimbo and La Serena —Earthquake and earthquake wave. A short 
 but terrifying subterranean noise, the precursor of an earthquake, in which the earth continued to 
 move without interruption, even though slowly, during the long period of 84 seconds. A barometer 
 hanging from the wall but separated from it by a space of 2 inches, swung from northeast to south¬ 
 west, and it became necessary to hold it, as it struck hard enough to have broken it. This movement 
 did not cause any damage to houses, but it was otherwise in the port of the city in the rise of the sea, 
 which occurred 10 minutes later. The water rose 16 English feet higher than high tide. The first 
 movement of the waves was in the direction from northeast to southwest, as it had been in the move¬ 
 ment of the ground. It caused great damage and destroyed almost completely several reverberating 
 furnaces and a canal. 
 
 1857, November 7, XI, 21. Copiapo —At the hour indicated there began a slow shaking of 
 the earth, which had not been preceded by any sound whatever. In 3 minutes the movement increased 
 and the earth trembled forcibly, so that buildings and trees were violently shaken and people walked 
 unsteadily in consequence of the violent oscillation of the ground. With each second the commotion 
 appeared to increase, and buildings were thrown out of plumb by the force of the shock. The 
 people ran together in the streets and plazas in consternation. Many people, especially the women, 
 kneeled imploring piteously the mercy of heaven. The earthquake continued with all its violence until 
 
 XI, 23, and then gradually the movement lessened until XI, 24, when it ceased.The Inten- 
 
 dente ordered an inspection of the city by the Director of Public Works of the Province, and it 
 appears from his report that adobe blocks (tapias) were thrown down from 38 houses and walls, 
 and that the water-pipes of some 10 places were destroyed. 2 
 
 1859, October 5, VIII and some minutes. Copiapo —The principal known details regarding 
 this occurrence are taken from the earthquake catalog of A. Perrey, of the year 1862. At the hour 
 indicated there occurred in Copiapo various horizontal shocks, from north to south, accompanied 
 by a terrifying noise. They lasted 4 minutes with their maximum force, and afterward decreased in 
 violence. The train from Caldera, which should have arrived at n h 30™ a. m., did not reach Copiapo 
 until 5 h p. m. In that port, where the shock lasted 2\ minutes, it caused many ruins. The damage 
 was considerable in Copiapo, where the Intendencia, the jail, the hospital, and the churches all suf¬ 
 fered greatly; 115 houses were thrown down and 224 remained uninhabitable. The losses were 
 estimated to be 930,000 pesos. 
 
 In Tierra Amarilla the first shock occurred at VII, 57, and lasted more than 2 minutes. The 
 buildings rocked like pendulums, and several were damaged. In the mine of Carmen Alto 8 or 10 
 miners were buried under rock falls. 
 
 The ground was cracked in various places, and particularly in the Plaza de Armas in Copiapo. 
 according to the statement made to the writer by an inhabitant. 
 
 In Caldera there was an earthquake wave, the sea sinking 19 feet below the level of ebb tide, 
 thus emptying a space of 150 varas in the port and occasioning considerable damage to the boats 
 anchored there. The after shocks were numerous. 
 
 This earthquake was felt in La Serena, but the area of its action was probably even much more 
 extensive. 
 
 1 Manuel Concha, Cronica de la Serena. 
 
 2 El Mituero de Copiapo of November 7 and II. 
 
Earthquake History of Atacama 
 
 19 
 
 Letter of the Superintendent to the Directors of the Copiapo Railroad. (2d semester of 1859, p. 6. 
 Signed Luis Lebreu. Extracted from the archives of the Intendencia of Atacama.) 
 
 “There have been no serious accidents which have occasioned either death or injury. Nevertheless, I should 
 mention here the fearful catastrophe of the 5th of last October, in so far as it affected this corporation, for it 
 caused an interruption of four days in the traffic. I refer to the great earthquake which, in less than two minutes, 
 destroyed innumerable houses and properties in this province. On the railroad between Copiapo and Caldera the 
 earth was torn from the rails for leagues. All the embankments were thrown more or less out of level. At other 
 points embankments 20 feet high disappeared, leaving the rails and ties scattered over the flat earth. In Caldera 
 the oven and chimney of the smelter were thrown down, the wharf was thrown badly out of level, and innumer¬ 
 able adobe blocks, both in the stations and in the walls along the road, were thrown down. The buildings of the 
 company suffered less because, being built of wood and cane, they resisted the earthquake much better in conse¬ 
 quence of their elasticity.” 
 
 1864, January 12, II, 9, Copiapo. Semiterremoto —The details which follow are taken from 
 the annual earthquake catalog of A. Perrey for the year 1864. He obtained them from El Con- 
 stituyente and from the Comercio of Lima for the 25th. 
 
 The temblor lasted 1 minute. Although it was longer than that of 1859, it was not as violent, 
 and did not do as much damage. It was accompanied by a very loud subterranean noise which began 
 only after the earth was moving. The shocks were distinctly directed from NNE. toward SSW., 
 but with a vertical movement from above downward (sic). Walls running north and south suffered 
 little, but those which were directed east and west received great damage. At least 12 shocks were 
 counted during the morning, and up to 3 in the afternoon frequent after-shocks and occasional sub¬ 
 terranean noises were observed. In Punta Negra houses were thrown down. Tierra Amarilla, on 
 account of its wretched construction, was almost completely ruined. Damage was done in the mines 
 of Elena and Transito del Cerro Ojancos and extended to Potrero Grande, Chanarcillo, and Tres 
 Puntas. Nothing occurred in Caldera, where not even an earthquake wave was observed. 
 
 The earthquake was felt in Freirina, where various persons were injured and a little girl was 
 crushed in the street of San Fernando. A house in Colipe Street was thrown down. In El Transito 
 (in the valley of the Huasco above Vallenar) 2 Argentine peons were crushed to death. (El Minero 
 of Freirina, January 23.) 
 
 1868. The great earthquake and earthquake wave of August 13 —The terremoto of August 13, 
 1868, devastated the northern part of Chile and the south of Peru. Numerous consecutive shocks 
 succeeded one another and were followed by a terrible earthquake wave, tsunami, which did great 
 havoc in the ports of both countries. The latter extended throughout almost all the immense area of 
 the Pacific, from the Antarctic lands to California and from Australia to New Zealand, as well as in 
 the scattered islands of Oceanica; and for the first time it was possible to gather a sufficient number 
 of observations to study the propagation of an earthquake wave across the ocean. Polo considered 
 this terremoto as the greatest which had occurred in these provinces of South America and even 
 more destructive than that of 1746, although it did not have so many victims. For these several 
 reasons we have to do with a great seismic phenomenon which deserves detailed study, for which 
 there are available a number of scientific articles of importance and interesting original documents. 
 
 It is not appropriate to the historical list of the earthquakes of Atacama to 
 reproduce here the full account of the effects of the earthquake of 1868 in the more 
 northern part of Chile and the south of Peru. It will be found in the Historia Sismica 
 de los Andes Meridionales, Segunda Parte, pp. 77-158. Atacama was several hun¬ 
 dred miles south of the region of great intensity, and the shock was but a moderate 
 one in that region. Montessus gives the following, pp. 94 and 95. 
 
 “ Copiapo —At 5 o’clock and 16 minutes there was felt a temblor of an unusual type of movement. I first 
 felt it in my bead as a giddiness. It seemed very slow and rhythmic, like that of a hammock or of a boat, but 
 without any vibration, so that the house did not even creak. The movement was wholly in a horizontal sense and 
 in a direction which could be clearly observed from north-northeast to south-southwest. The interval from the 
 time when I first noted the temblor to its conclusion was two minutes and thirty seconds, but others whose state¬ 
 ments are worthy of credit assert that it lasted four minutes. I believe this to be quite possible, because it is evi¬ 
 dent that I did not observe it until it had already been in progress for some time.” (Carvajal, Rector del liceo.) 
 
 Montessus also quotes the following: 
 
 “ At XVII a temblor of to 3 minutes duration alarmed the city. The movement began gently, so much 
 so indeed that it was mistaken for that which was produced by carriages. But by degrees it increased in strength 
 until it was difficult to remain erect without staggering. Fortunately the oscillation was slow and nearly all the 
 
 3 
 
20 
 
 Earthquake Conditions in Chile 
 
 buildings were of wood and adobe. The temblor was neither preceded nor accompanied by any sound, a rare 
 circumstance, but one quite like that which was experienced in Copiapo when Mendoza was destroyed by the 
 earthquake of 1861.” (Gutierrez, Melchor. Estadistica del horrible cataclismo de 13 de Agosto de 1868. 
 Valparaiso, 1870.) 
 
 (The great earthquake of May 9, 1877, like that of 1868, was extremely violent 
 in southern Peru and northern Chile, but was felt only as a strong shock in Atacama. 
 Montessus gives a full discussion of the terremoto, Historia Sismica, Segunda Parte, 
 pp. 162 to 223, from which we may take the following notes regarding its effect in 
 Atacama.) 
 
 “Copiapo —Strong temblor. No injuries. The first movement occurred at XX. 20 (Diario Oficial). The 
 duration was estimated at 4 minutes. 
 
 “ Chanarcillo and other places in the valley of Copiapo —A strong shock was experienced. 
 
 “ Puerto del Huasco —The temblor occurred at XX. 20. It was strong and was prolonged during 3 minutes. 
 There were no accidents either on land or sea. (Report of the Subdelegado Maritimo.) 
 
 “ Carrival Alto and Carrical Bajo —The earthquake was felt at XX. 30 and the movement seemed to come 
 from the north. 
 
 “ Freirina —Temblor which lasted 3 or 4 minutes. 
 
 " Vallenar —A strong, undulating temblor without preceding sound. It lasted 2 minutes and the movement 
 seemed to be horizontal. (Diario Oficial.) 
 
 “La Serena —The shocks began at XX. 31 mean time (tiempo medio) according to a clock whose exact¬ 
 ness was frequently checked. The shock moved from north to south, with east-west oscillations. There was no 
 sound preceding the temblor, which lasted 1 minute and 58 seconds. The movement of oscillation was slow but 
 very strong. I did not note the sharp shocks that commonly characterize terrestrial temblors. On the contrary, the 
 extraordinary slowness of the oscillations was comparable with the movement which may be felt when on board 
 a vessel in a tranquil sea. (The report of the German consul.) 
 
 " Coquimbo —The temblor of the 9th occurred at 8 h I5 m p. m., producing a prolonged movement of the 
 earth which lasted at least 4 minutes, according to the most general estimate. It was, however, without premoni¬ 
 tory sound, so that many did not notice it. Most of those who felt it said that they experienced a dizziness which 
 they could not explain until they recognized by the oscillations or movements of the lamps that there was an earth¬ 
 quake.” (Report of the Gobernador Maritimo.) 
 
 The above notes are taken from Eugen Geinitz, Das Erdbeben von Iquique 
 am p mai i8jp, und die dnrch dasselbe verursachte fluth ini Grossen Ocean. (Nova 
 Acta d. Ksl.-Carol.-deutschen Ak. d. Naturfor. Bd. XL, Nr. 9, Halle, 1878.) 
 
 Vallenar —August 29, 1877, semi-terremoto; December 3, 1903, terremoto; March 19, 1904, 
 terremoto. 
 
 [These occurrences of more or less severe shocks are listed by Montessus without details.] 
 
 1918, December 4, Copiapo 1 —This severe shock was too recent to have been 
 included by Montessus de Ballore in the Historia Sismica. Fortunately, there is a 
 complete report by a competent engineer, which we take from the Boldin Minero. 
 
 “ Near the beginning of the current year I received from the Minister of Industries instruc¬ 
 tions to investigate the effects of the terremoto of December 4, 1918, at Copiapo. 
 
 “ For this study I had at my disposal no more than 14 days. Consequently I was obliged to 
 limit my investigations to the city of Copiapo itself and its immediate vicinity, this course being the 
 more urgently imposed by the fact that the city had suffered the greatest damage. Nevertheless. 
 I made an opportunity to visit the port of Caldera for several days, where I was furnished with 
 important data relating to the great movements of the sea during the terremoto, and where I expected 
 to find opportunity to observe any permanent elevation or subsidence of the coast. 
 
 “ I must furthermore observe that this statement of facts is based in part upon reports whose 
 accuracy it was impossible for me to check personally. However, of the many accounts received, 
 I have used only those which came from persons who by their standing and personal qualities inspired 
 confidence in the exactness of their observations. I owe very important and reliable data to Senor 
 Luis Sierra Vera, who also supplied the facts regarding the hour, the duration and other phenomena 
 of the seism which are included in the following account. 
 
 1 Linneman, Clemens, Report of the Servicio de Minas i Jeologia. Copied and translated from the Boletin 
 Minero de la Sociedad Nacional de Mineria, pp. 412-420, 1919. 
 
Earthquake History of Atacama 
 
 21 
 
 “ The principal movement was preceded during the same day by premonitory temblors of little 
 importance. The first took place at o h 30™; the second at y h 43 m . The principal movement began at 
 7 h 44 m - If commenced with weak oscillations which gradually increased to a temblor of higher grade. 
 The most violent shocks lasted 3 minutes. Oscillations of minor grade followed during 2 minutes 
 and 53 seconds, so that the duration of the total movement was 6 minutes. 
 
 “ No subterranean sounds were heard either before or during the temblor. 
 
 “ The movement was composed of horizontal oscillations in which no particular direction pre¬ 
 dominated. Simultaneously with these oscillations, a number of vertical shocks of great violence 
 were experienced. 
 
 “ Among the effects of the terremoto, those which take first place are the damages to houses. 
 Even a superficial inspection of the streets in which the greatest damage was done developed evidence 
 of a vertical force. In support of this assumption we may cite: 
 
 “(1) The collapse of flat roofs, where not accompanied by serious damage to the surrounding 
 walls which supported them. 
 
 “(2) Regular cracks extending from the roof to the ground along the dividing-lines between 
 the houses. 
 
 “(3) Numerous cracks which extended from the corners of the doors and windows toward 
 the roof in one direction and toward the ground in the other. 
 
 “ The failures indicated under 2 and 3 are typical of irregular vertical stresses where houses 
 collapsed, for the points in which they were manifested are the weakest with reference to such forces 
 as those which are considered. In the course of my activity as an expert, appointed by the courts of 
 justice to study the damage caused by mining in the densely populated coal-producing district of 
 Rhenish Westphalia, I had repeated opportunity to observe these relations. We must, therefore, 
 reject the statements of some persons in Copiapo that no other movements than those of oscillations 
 of the ground were to be observed. The violence of the vertical shocks is demonstrated by the fol¬ 
 lowing fact: The safe in the steel vault of the municipal treasury, standing on a wooden box, was 
 thrown violently upward and left definite holes in the paper on the wall, from the height of which 
 one may form an idea of the violence of the movement, even after deducting the difference which 
 would correspond to a probable subsidence of the ground. 
 
 “ Nevertheless, there is no question that the principal cause of destruction was the horizontal 
 component. In regard to the direction of the horizontal movements, there is a great diversity of 
 observations. Some thought they had observed an east-west direction, others a movement from 
 north to south. Senor Sierra, whose statements in regard to this point inspire the greatest confi¬ 
 dence, describes the seism as a shaking without pronounced determinate direction. The cracks which 
 opened in the earth during the terremoto, regarding which I shall have more to say later on, also 
 failed to indicate a definite direction. Furthermore, the damage caused by the cracking of walls and 
 houses was distributed equally in the surrounding walls without any predominant orientation. 
 
 “ The destructive action of the terremoto was enormous in the city. Of 1,630 houses not less 
 than 344, that is 20.9 per cent, were completely destroyed. Those which were seriously damaged 
 numbered 349, or 21.3 per cent. The remainder, 944 or 57.8 per cent, suffered comparatively little 
 damage, but nevertheless, not a single house escaped intact from the catastrophe. 
 
 “ In order to get a definite idea of the effect of the terremoto of December 4, 1918, in the 
 destruction of the city, it is necessary to consider, even though only in a summary manner, the differ¬ 
 ent classes of buildings, the condition of the different edifices, and the subsoil of the built-up area. 
 
 “ The city of Copiapo is built in large part upon the sandy clays of fluvial deposits of the river 
 Copiapo, and stands in a very unfavorable situation, since it is exposed to inundation by the floods 
 of the river, such as that which occurred in 1906. The houses are in large part very old, many of 
 them dating back 60 to 80 years. Those which are not more than 10 or 15 years old are few in num¬ 
 ber and are found chiefly in the center of the city. Rented properties predominate. The number of 
 houses in private hands is very small. In consequence of the decay of the city caused by the aban¬ 
 donment of the mines, the number of inhabitants has fallen off in the last decade and rentals have 
 been correspondingly reduced. The maintenance and repair of houses has correspondingly decreased 
 in consequence. When to these conditions we add the losses caused by the inundation of 1906, it may 
 be understood that at the date of the terremoto of Copiapo the state of the buildings was deplorable. 
 
 “ In the following description I will refer only to the principal types of construction, each one 
 of which is linked with the others by transitional examples. The proportion of each type to be found 
 among the buildings of the city is practically the same, as may he seen by the statistics which are 
 appended at the close of this statement. 
 
22 
 
 Earthquake Conditions in Chile 
 
 “ The oldest and cheapest houses, which for that very reason are inhabited by people without 
 means, are those built of tapiales. This type of construction is employed chiefly for interior walls. 
 The material (mud) is pounded into blocks i meter high, more or less, 1.5 meter long, and 0.5 meter 
 thick. The mud is made by the clayey sediment deposited by the River Copiapo, which is compressed 
 in a mold. The blocks are placed one upon another to the height of 2 meters, more or less, which 
 with rare exceptions are not tied together or held by mortar of any sort. Indeed, in general they do 
 not even take the precaution to strengthen this material with straw, even though it is but slightly 
 coherent, because of the large proportion of sand which it contains. Generally a number of layers 
 of adobes of the same material are placed upon the blocks, and the rafters rest upon these. The walls 
 are covered with a thin coating of mud which is made to adhere by means of sticks or nails placed 
 wherever practicable in the walls for this purpose. The roof, which in most of the houses is rather 
 low, is composed in these, as well as in the other types of construction, of a supporting frame which 
 is covered with cane or reeds. In order to protect it from wind or rain, it also is covered with a thin 
 layer of mud. This deteriorates, but not uniformly, and thus needs to be repaired year after year, 
 and, as the simplest method, is covered with a new layer. Thus after a few years a very thick cover¬ 
 ing accumulates, which lessens the stability and resistance of the structure with reference to shocks. 
 
 “Of great advantage for its cheapness is the widely employed method of building with adobe 
 brick. The material is the same as that of the tapiales. but the walls are thinner and the building as a 
 whole is thus lighter. Beyond that, the placing of the adobes and the mud stucco is the same as in 
 the previous case. It is, however, a general practice to reinforce the adobe brick by means of wooden 
 beams. 
 
 “ This type of construction constitutes in a certain degree a transition to the structures which 
 are more modern but more costly and in which cane and sacking are used. The sacking is done up in 
 smali bundles and placed between the uprights, which are fairly close together. The whole is covered 
 with a layer of mud, according to custom, and the latter adheres much more firmly. 
 
 “ In those cases where Guayaquil cane is used, the canes are nailed horizontally across the 
 uprights, one above the other. Thus two walls are produced, one inside and one outside, and the 
 space between the two is not filled. This type of construction is very durable and, because of its 
 elasticity, resists shocks strongly. But it is not very much used because of the high price of the cane, 
 which is imported from Ecuador. On this account it is found principally in business houses and in 
 the residences of persons of means. 
 
 “ These four types of construction were found to be distributed in the following proportions 
 
 among the 1,630 houses examined: 
 
 Per cent 
 
 Tapiales .440.... 26.8 
 
 Adobes .349....21.3 
 
 Frame and sacking ..405....24.7 
 
 Guayaquil cane .446....27.2 
 
 “ There are some other types of construction which occur in such small numbers that it is not 
 worth while to consider them. If we consider the damage occasioned by the terremoto in each of 
 these different kinds of buildings, we shall see that the destruction is much the more general in those 
 of tapiales. Already weakened by the spalling and cracking of the surfaces at the contact of the 
 blocks, the tapiales would not have resisted a temblor of even moderate intensity, decidedly inferior 
 to that of December 4. 
 
 “ The blocks placed one upon another simply fell off and in some cases crushed the inhabitants. 
 The resistance of the houses of Guayaquil cane was very much greater. The damage consisted almost 
 exclusively of cracks of little moment and in the fall of plaster. In the cases in which there was grave 
 damage or total ruin the results may be attributed to the age of the building or the defects of 
 construction. 
 
 “A very fair, though less effective, resistance was offered by the houses of sacking. This con¬ 
 struction also is very light and elastic. There is no doubt that if Copiapo had been built of lighter 
 material, such as wood frames with sacking and cane, as is the case in the ports of the province, we 
 would not have had to consider this earthquake as one of maximum grade, according to the esti¬ 
 mates in general use. 
 
 “ The number of adobe houses which were totally destroyed or which suffered severe damage 
 is considerable. Unfortunately, as I have already indicated, it was not possible for me in the course 
 of my investigations to distinguish between those buildings of adobe brick which were not rein¬ 
 forced by any structural frame and those in which a frame of wood or other material had been used ; 
 but it is quite certain that the percentage of houses of the latter class must have in a measure favor¬ 
 ably influenced the proportion of houses in which there was but little damage as compared with those 
 in which the damage was serious. 
 
Earthquake History of Atacama 
 
 23 
 
 Statistics of Damage to Different Types p er 
 
 cent 
 
 Tapiales . 440 
 
 Totally destroyed .249....56.6 
 
 Seriously damaged .138-31.4 
 
 Slightly damaged . 53 - 120 
 
 Adobe bricks . 349 
 
 Totally destroyed . 57.... 16.3 
 
 Seriously damaged .106... .30 4 
 
 Slightly damaged .188....53.3 
 
 Frame with brush and adobe.403 
 
 Totally destroyed . 54 -*-- 8.4 
 
 Seriously damaged . 81....20.0 
 
 Slightly damaged .290....71-6 
 
 Frame buildings with Guayaquil cane.446 
 
 Totally destroyed . 4 -*«* °-9 
 
 Seriously damaged . 2 5 -5-6 
 
 Slightly damaged .. 4 I 7 ---- 95-5 
 
 “ With respect to the importance to be attached to the character of the subsoil in the distribu¬ 
 tion of damage in the city, it is difficult to obtain statistical data. It would appear, nevertheless, that 
 that part of the city which is located on firm ground suffered in general less, in spite of the fact that 
 
 Fig. I —Diagram showing proportion of total destruction (black), serious 
 damage (crossed), and slight damage (white) in houses of tapiales (a), 
 abode bricks ( b ), frame with brush and abode ( c ), and frame buildings 
 with Guayaquil cane (d). 
 
 there were many houses of poor construction and many old ones. This is readily understood, for the 
 firm ground transmits the oscillations more uniformly to the structures, while the terrane of clayey 
 or sandy alluvium, but slightly compacted, exhibits cracks and local disturbances which indicate 
 tension and unequal strains in the subsoil, the inequalities of which must have produced more serious 
 damage in the edifices built thereon. 
 
 “ I observed numerous cracks and local disturbances of level, which appeared to be phenomena 
 connected with the earthquake, in the garden of the German high school and in the vicinity of the 
 corral of the municipal inspeccion de obras publicas. In the latter place the principal crack was 100 
 meters in length, more or less, and 0.30 meter wide. Its course was S. 75 W. The visible depth was 
 0.70 meter: below that it was full of clods and earth. One of the two cracks in the garden of the 
 German high school measured 8 meters in length, 0.20 meter in width, and 6.30 meters in depth. Its 
 course was N.-S. 
 
 “ On one side of this crack the ground was raised and had therefore experienced a very severe 
 shock. It had nothing to do with a sinking in or faulting. I was told that in several streets there had 
 been similar occurrences, but I was unable to verify these statements. 
 
 “ With respect to the formation of cracks in firm ground I was unable to secure definite proof. 
 It seems appropriate to mention the following interesting fact: Shortly after the earthquake a large 
 quantity of water invaded the mines of Agustina and Bateas in Tierra Amarilla. The mine was 
 already inconvenienced by the large quantity of water. As the amount varied with the flow of the 
 River Copiapo according to the proportion used for irrigation, there could be no doubt that the 
 water came from the river. The earthquake caused such an increase that it was feared that the water 
 would flood the entire mine, but after a few days the influx returned to its normal amount. This 
 phenomenon may be explained by the formation of a new group of cracks which provided a new 
 outlet for the waters of the river connecting with the old cracks that had given the water access to 
 the mine. With the formation of the new cracks the clay sediments of the river were washed down, 
 
24 
 
 Earthquake Conditions in Chile 
 
 giving to the water a muddy appearance. As the water began to diminish in volume and to recover 
 its usual color, we may infer that the sediment which it had carried closed the system of cracks until 
 they again became unimportant. 
 
 “ I have not been able to observe any subsidence or elevation of the ground; at least, that was 
 the result of my investigations. My observations on the coast gave a negative result. In Caldera, 
 where the temblor was strong, I was assured by those who had seen the phenomena that shortly after 
 the shock the sea withdrew considerably and afterward rose to 5 meters above the normal tide. This 
 movement was repeated four or five times, but none of the observations permits us to draw any infer¬ 
 ences in regard to even a minimum change of level of the coast. 
 
 “ Herewith the data which I personally secured regarding the action of the terremoto come to 
 an end. I subjoin in an appendix certain reports which refer to the country round about and to some 
 points distant from Copiapo. I owe them in large part to Don Luis Sierra, Vera.” 
 
 Caldera —(1) Duration of the terremoto, 6 minutes; direction N. 80 W. The cross of the 
 church fell forward in the same direction. Heavy sideboards were moved in that direction. Almost 
 immediately after the terremoto the sea began to withdraw and moved back and forth. The sea 
 withdrew in Puerto Ingles. The normal advance of tide is about 27 meters, measured across the 
 beach. The sea advanced 39 meters at the point where the beach begins at the north. The tides are 
 generally equal in all parts of the beach, but toward the south their range at one point was 24 meters, 
 at a second point further south 17 meters, and at the end of the beach 55 meters. In Calderilla the 
 normal tide is 11 meters at the beginning of the beach next to the bridge, but here the sea after the 
 earthquake rose 48 meters and at the opposite extremity to the south 141 meters horizontally. No 
 change of level was observed in the coast. In the lawn-tennis beach cracks appeared at a distance of 
 200 meters from the beach and parallel to it. Damages: In the stores the window glass was broken. 
 There were no cracks in the houses, not even in the old ones. All the houses are of wood (boards). 
 The street lamps were shaken. It was difficult to walk during the temblor. The water in the wells 
 remained at constant level. No subterranean sounds were heard. After the temblor low subterranean 
 sounds were heard until January 17, 1919. The vertical movement could be felt by individuals in their 
 own persons. There were some gyratory movements, but these were observed only in heavy objects, 
 whereas the light ones moved in the direction already indicated. On a board covered with powder, 
 figures and heaps were formed as if it had been hit from below upward. Three classes of movements 
 were noted, vertical, horizontal and rotational. 
 
 (2) The wharf of the railroad was damaged by the earthquake. The sea withdrew slowly, 
 leaving the passenger wharf high and dry, shortly after 8 o’clock. The movement was slow. The 
 sea afterward returned, slowly inundating the beach, and almost overtopped the wharf, the height 
 of the movement attaining 4.5 meters. The length of the wharf is about 70 meters. On board a 
 vessel the crew experienced a vibration and were alarmed by the creaking of the beams. With respect 
 to change of level of the coast it can not be stated whether the level is the same as before or whether 
 it has suffered a change which is so slight that it can not be observed. On the high seas there was a 
 strong shock which was communicated to a ship, and the passengers thought that they had struck 
 something. 
 
 (3) The principal direction of the seism was from west to east. Vertical shocks were not 
 perceived. 
 
 (4) There were large movements after the earthquake. The sea withdrew four or five times 
 and returning rose to a height of 5 meters above normal tide. The waves produced by the earthquake 
 had a N. S. direction, which is considered out of the common. There were strong movements of 
 boats anchored in the ports, accompanied by strains in the chains of the anchors and the capstans of 
 the boats. 
 
 Monte Amargo (between Copiapo and Caldera)—During the night of December 5-6 much 
 strong subterranean noise was heard only in the ravines. 
 
 Potrcro Scco —Moderate damage done to walls of tapiales and houses. Nothing occurred in 
 Hornito. 
 
 Pueblo Hundido —There was a very strong temblor. 
 
 Punta Colorado ■—A slow temblor was experienced. The train was stopped. The oscillations 
 were transverse and slow, as if one were in a hammock. The duration of the temblor was 2 minutes. 
 In kilometer 530, between Almarante Latorre and Quebrada Grande, there was a rock-slide which 
 obstructed the track. The train moved back and forth, the wheels turning a little. 
 
 Puquios —It is not possible to state with exactitude from what direction the movement came. 
 The phenomenon began with a slight noise, but just before the beginning of the strong vertical move¬ 
 ment was a deep, powerful subterranean sound. Afterward and continuing until February strong 
 sounds were heard, some of them short and hard like the discharge of a cannon and others long and 
 
Earthquake History of Atacama 
 
 25 
 
 intermittent like echoes, but these were not accompanied by any movements. In the town of Puquios 
 not a single edifice escaped without some damage. Several houses and walls fell into the street, some 
 lengthwise and some across. In the works of the Dulcinea mine, including the administration build¬ 
 ing and houses of the workmen, scarcely anything remained standing. The buildings, including those 
 of the administration, had walls of tapiales or adobe. The inclosures of tapiales fell almost without 
 exception. They were not overthrown, however, as is commonly the case, but were completely demol¬ 
 ished. In the works there are two wells 35 meters deep, in which the water has increased about 
 25 per cent. In various places small cracks or superficial fissures have opened in the meadows. The 
 several wells in this vicinity have not shown any change. There have been no changes of level of 
 the ground. 
 
 San Antonio i Loros —Several houses have been damaged by the terremoto, some have been 
 destroyed, and numerous walls have been thrown down. Several irrigation canals have been com¬ 
 pletely ruined. In the hacienda El Fuerta, 2 or 3 leagues south of San Antonio, the houses were 
 thrown down. 
 
 Tierra Amarilla —The earthquake was less severely felt here than in Copiapo and did not do 
 any considerable damage. 
 
 Tres Puentes —Many slides obstruct the wagon road. 
 
 Vallenar —A strong temblor. People ran out into the street and patios. Many objects were 
 overthrown. In the building of the Seccion Industrial del Instituto Tecnico Comercial there are 
 cracks, among which the vertical ones predominate, almost always in the eastern or western sides. 
 There were none in the other direction. The separation of the walls in a vertical sense is readily 
 noted at the joint of the adobes with the uprights. They have separated so far that the light shines 
 through and one may see through to the other side. In the first story, however, there is hardly any 
 damage, except in the Seccion Industrial, and even there there is nothing more than one floor with 
 small cracks in the N. S. wall. 
 
TERREMOTO' OF NOVEMBER 10 , 1922 
 
 IMMEDIATE ANTECEDENTS 
 
 While Chile rightly has the reputation as a whole of being an earthquake region, 
 it is nevertheless true that it may be divided into several different earthquake prov¬ 
 inces, each of which is distinguished geographically from the others by the occur¬ 
 rence of shocks that are peculiar to it, both as to extent and intensity. The southern 
 portion of the inhabited region, south of latitude 36°, of which Concepcion is the cen¬ 
 tral point, is comparatively free from shocks. Valparaiso and Santiago, in latitude 34 0 , 
 are central in an area of extreme activity, which extends northward up the coast to 
 about latitude 32 0 . Copiapo, in latitude 27 0 , lies in a third province of somewhat more 
 moderate activity; and northern Chile, comprising the district from Antofogasta to 
 Arica, is again relatively inactive. Still further north, in southern Peru, in the 
 vicinity of Arequipa, is the most active earthquake province in all South America. 
 
 The terremoto which gave rise to this report occurred in the province of Ata¬ 
 cama, in which Copiapo is situated, but its vibrations extended sensibly beyond Con¬ 
 cepcion on the south and northward beyond Iquique. It was, therefore, an extremely 
 widespread phenomenon. It is possible that the conditions that led up to it may have 
 been connected with the seismic activity of the entire coast. It is therefore desirable 
 to note the temblors which occurred during the preceding month of October. 2 
 
 October 4 —Temblor in the south. According to advices received yesterday by the State tele¬ 
 graph, a strong earth tremor was felt shortly after noon in the south. It occurred at I2 h I 2 nl p. m., 
 with the center in the vicinity of Constitucion, where the quivering of the earth was most intense. 
 The tremor was also felt with force at Parral, Ouirihue, and Empedrado. 
 
 October 11 —Washington, D. C. The seismographs in this capital registered this morning one 
 of the most violent earthquakes of which there is record. The center is estimated to be 3,800 miles 
 south of this city (3,800 miles corresponds to 55 degrees of latitude, and, measuring from Wash¬ 
 ington, this places the earthquake in latitude 16 south, in southern Peru). The estimate thus agrees 
 with the advices from Peru, which follow. 
 
 October 12 —Lima, Peru. An intense earthquake yesterday shook an extensive zone in the 
 southern part of Peru, occasioning considerable damage in Arequipa and elsewhere. The railroad 
 line between Arequipa and the coast suffered appreciably. Telegraphic communication with the 
 south was interrupted. 
 
 October 16 —Lima, Peru. Notices continue to be received regarding the earthquake in the 
 south. The movement was confined to the department of Arequipa; Camana, Caraveli and Arequipa 
 suffering most In Arequipa certain buildings fell and others were seriously damaged. There were 
 no deaths, but the number of wounded is very large. The material losses are great. 
 
 October 17 —Santiago. In Constitucion, according to telegraphic advices, a strong earth 
 tremor was felt a little after 5'’ 30™ p. m. It extended throughout the department. This shock was 
 not registered by the seismographs in this capital. 
 
 1 Terremoto, in the usage prevailing in Chile, signifies a destructive earthquake and contrasts with temblor 
 which is used to designate an earthquake of less severity. Thus the earthquake of November 10, 1922, is called a 
 terremoto in Copiapo, Vallenar, and other places where its effects were disastrous; but it is more appropriately 
 described as a temblor in Valparaiso and Santiago, where the public was startled but no damage was done. We 
 unfortunately have no similarly convenient terms in English; but the words terremoto, earth movement, and 
 temblor, earth quiver, may well be adopted and used with their Chilean signification. That usage is to be under¬ 
 stood wherever they appear in this report. 
 
 2 The data here cited are taken from the daily paper, El Mercurio, Santiago. 
 
 26 
 
Terremoto of November io, 1922 
 
 27 
 
 October 22 —Santiago. A strong temblor. In the midst of the play at the theater last evening, 
 at n h 30™ p. m., there was felt a formidable temblor which alarmed the entire population. A panic 
 was produced in the theater, which was fortunately only momentary. When the tremor had passed 
 the play was resumed. Six ladies were assisted from the theater in a swooning condition. At mid¬ 
 night a strong subterranean noise was heard, not accompanied by a sensible movement. 
 
 October 28 —Concepcion. In the early hours of dawn today people were violently awakened 
 by a terrible temblor which alarmed the entire neighborhood. The movement was of little duration, 
 but of such intensity that if it had been but a few seconds more prolonged Concepcion would prob¬ 
 ably have been reduced to ruins. The entire population ran into the streets in panic, many without 
 clothing and others half dressed. The outcries of the people and the desperate flight of many, with the 
 noise of falling shelves in stores and of breaking doors and windows, increased the general con¬ 
 fusion. Fortunately, when the first moments were passed it was seen that the temblor had not caused 
 the damage which at first was feared, the destruction being confined to the window panes of various 
 galleries and doors, and so forth, and the show cases in the shops. 
 
 A short time after the first shock others of much less violence were felt, even though they were 
 accompanied by subterranean noises. A large part of the people passed the night in the streets or in 
 the patios of the houses. It is the general opinion that it is many years since there has been so violent 
 a temblor at Concepcion. 
 
 The greatest damage done consists in the cracking of walls of various houses, especially those 
 of stucco and those which were adorned with heavy ornaments. In the jail of the Comissaria, an old 
 building of poor construction, part of the roof of one of the interior wings fell with a wall. There 
 were no personal injuries. 
 
 Notices from Tome, Coronel, Lota, Talcahuano, describe a sharp shock but no damage. From 
 Chillian it is reported that at 3 1 ' 15 1 " a. m. there was felt an extremely violent temblor which greatly 
 alarmed the people. The oscillations were determined as being from southeast to west, and it is 
 stated as a fact that a long time has elapsed since an earth-shock of equal intensity with that which 
 occurred to-day has been experienced. 
 
 October JJ —Temuco. At 3 11 8 m on Saturday morning three temblors were felt, which caused 
 
 no little alarm. 
 
 Coigiie. At 3 h I5 m on Saturday morning there was a severe temblor, which lasted about 15 
 seconds and alarmed all the neighborhood. 
 
 November 8 —Copiapo. In the late hours of the afternoon, at 6 h 30™ p. m. today, this city 
 experienced a prolonged temblor, that caused great alarm in the entire population. The movement 
 was relatively gentle but of very great amplitude, so that people rushed into the streets in panic, 
 fearing with good reason that the shock was a recurrence of one of those great earthquakes which 
 have repeatedly devastated this region. Advices from neighboring places indicate the temblor was 
 felt generally, but did no damage. 
 
 The preceding notices suffice to demonstrate that there was general activity in 
 the earthquake zone of Chile and southern Peru throughout its entire length, in the 
 autumn of 1922. The terremoto of October 11 at Arequipa, although not very 
 destructive, was apparently severe enough to relieve the strain in that region, for 
 there are no reports of particularly heavy after-shocks. The north-central district of 
 Chile, comprising Copiapo, had no part in the movements until November 8, and 
 appears to have been a locus of gradually increasing strain. In Santiago, in the 
 south-central province, there was a strong temblor on October 22, and the southern 
 province, comprising the area around Concepcion and Constitucion, was the scene 
 of repeated though moderate activity throughout the month of October. 
 
 In each of these districts the shocks experienced during these weeks were of 
 unusual severity; that is to say, they exceeded in violence anything within very recent 
 experience; and they may be regarded as representing the culmination of a strain 
 of moderate severity, in all the districts except that of Copiapo. In the latter the 
 strain had attained proportions which could be relieved only by movements of disas¬ 
 trous effect. 
 
28 
 
 Earthquake Conditions in Chile 
 
 In thus considering the terremoto of November io as an incident in the general 
 activity of a zone 1,500 miles (2,500 km.) in length, we are linking together local phe¬ 
 nomena, each of which no doubt is related to geologic conditions peculiar to the prov¬ 
 ince in which each separate temblor occurred. Because of the disjointed condition of 
 the materials, the rocks, it is impossible that there should be continuity of effect 
 throughout so extended a mass. This is obviously true when we consider the numer¬ 
 ous faults and volcanic intrusions by which it is divided into blocks of irregular shape. 
 In the vicinity of Arequipa the mountain trends are northwest and southeast, depart¬ 
 ing at an angle of 45 0 or more from the north-south ranges of Chile. Throughout the 
 latter there are many points of division indicated by short mountain ranges and basins 
 that have the aspect of Basin Range structure. Volcanoes stand aligned along great 
 fractures, several hundred miles in extent. Intrusions of various kinds of igneous 
 rocks, ranging from granite to basalt, form a complex that is extremely hetero¬ 
 geneous in its capacity to transmit pressure or elastic waves; and these rocks are, 
 superficially at least, so crushed that there are but few masses that would yield a 
 respectable building stone. 
 
 From these facts it follows that unity or continuity of activity can not be re¬ 
 garded as a result of continuity of structure throughout this long earthquake region. 
 The superficial facts would, on the contrary, lead us to expect local manifesta¬ 
 tions of the relief of strain; and yet it is evident from the wide distribution of the 
 shock of November 10 that it was a general, not a local, phenomenon. To be sure, it 
 did not extend to Arequipa; but throughout the north-south range of the Chilean 
 coast, from Iquique to Concepcion, a distance of 1,250 miles (2,000 km.), it was dis¬ 
 tinctly felt, with intensities represented by V or more of the Rossi-Forel scale. From 
 southeast to northwest the diameter of the isoseismal of intensity IV or more appears 
 to have attained 1,625 miles (2,600 km.), for Buenos Aires reported a strong temblor, 
 and the island of San Felix, situated in the Pacific Ocean, 500 miles (800 km.) west 
 of the Chilean coast, was notably shaken. 
 
 The vast extent suggested by these superficial linear dimensions indicates great 
 depth of origin. It will appear in the discussion of the geologic structure of the 
 region of maximum intensity that the pressure to which the earthquake is attributa¬ 
 ble originated beneath the Pacific Ocean, and that the shock was propagated east¬ 
 ward in the direction of thrust-planes lying at a low angle beneath the Pacific and 
 the Cordillera of the Andes. With this concept in mind, we are in a position to under¬ 
 stand how it is that the great terremoto affected the entire earthquake zone, in contrast 
 to the many local temblors which have been recorded as distinct occurrences in sepa¬ 
 rate parts of it. The great earthquake appears to correspond to movement on a very 
 deep-seated, widespreading thrust-fault, while each of the minor occurrences may 
 be regarded as representing the relatively superficial displacement of a segment of 
 the general structure. This view of the relation of the parts to the whole and of the 
 controlling structure was reached only after prolonged study on the ground. 
 
Terremoto of November to, 1922 
 
 29 
 
 EXPERIENCES in the terremoto 
 
 At Copiapo 
 
 On arriving in Copiapo the writer received from Dr. Luis Sierra Vera a very 
 accurate account of the earthquake of November 10, 1922. Dr. Sierra had experi¬ 
 enced many earthquakes and some severe ones. He was accustomed to observe them 
 and had formed the habit of promptly noting the times of beginning and passing of 
 the different phases which might occur. His residence was situated in the upper part 
 of Copiapo on the alluvial fan which descends from the high mountains on the east 
 and which is composed chiefly of loose cobbles and sand, but is thoroughly drained. It 
 was compact enough to constitute a fairly good foundation, and houses in that sec¬ 
 tion were not materially damaged when well built, as was Dr. Sierra’s. He was 
 reading when the thunder of the approaching earthquake announced it. He rose to 
 his feet, placed his watch on the table, took out his notebook, and wrote “ Maximum 
 grade.” It was my privilege to see the notes which followed and, lacking the tran¬ 
 script which I had hoped to receive from Dr. Sierra, I quote the record from memory, 
 as follows, in translation: 
 
 Preliminary tremors 1' 30"; violent phase 3' 30" ; diminishing 2'; two very strong shocks 30" ; 
 coda 4'. Total duration 11' 30". 
 
 Dr. Sierra described the terremoto as one not only of long duration but also of 
 great violence, and this latter impression was confirmed in conversation with other 
 residents of Copiapo who had experienced the earthquake of 1918. Nevertheless, it 
 appears from the studies of tapiales, that is of the walls which were partly over¬ 
 thrown, that the actual acceleration did not exceed four-tenths of the acceleration 
 of gravity and was in general considerably less. That is to say, the shock did not 
 attain the extreme violence reached by some of the most severe earthquakes on 
 record, and was probably comparable with the earthquake of September 1, 1923, in 
 Tokyo. The great damage sustained by the cities in its path was due to its prolonged 
 duration and to the very bad condition of many of the buildings exposed to it. 
 
 Questionnaires —It being impossible to interview personally any considerable 
 number of individuals in the different towns or throughout the province, a question¬ 
 naire was prepared, with the aid of Dr. Sierra, and was officially distributed by the 
 Governor of the Province of Atacama, Dr. Luis Romero. About a thousand were 
 sent out and some three hundred were returned. The information which they contain 
 varies greatly in character, and the labor of digesting the answers to the questions 
 was considerable. We are again indebted to Dr. Sierra for the summary of results 
 given in Appendix II. In the following notes, the data contained in a number of the 
 questionnaires are arranged for the convenience of the reader, somewhat in narrative 
 form, but with strict adherence to the facts as stated by the individual contributors. 
 
 Residents of La Serena 
 
 (1) Professor Gustavo Lagos, residing on Calle Infanta, was standing in his house facing 
 north. He heard no premonitory sound. He perceived no other indication of the beginning of the 
 shock than the movement. It came from the north. The hour was 23** 50™ by city time. The dura- 
 
30 
 
 Earthquake Conditions in Chile 
 
 tion was 3 minutes, more or less. He went out into the patio and observed that the sky was clear, 
 the stars shining; but afterward it clouded over and there was lightning. 
 
 The movements varied in intensity. They appeared to be in a vertical direction, from below 
 upward. They were all sharp from the very beginning and all of the same kind. There were about 
 three strong following shocks between I2 h 30“ and 3 h a. m. 
 
 The walls of the house were not cracked, except slightly at the corners. It was built of adobe 
 brick with wood ties and stood on a compact gravel formation. The roof was of corrugated iron on 
 wood rafters. The furniture was not thrown down, but one vase fell from a table. 
 
 (2) Sehor Eulijio Robles Rodriguez, Ministfo of the Court of Appeals, was in his library and 
 had just risen to his feet, facing east. He afterward did not remember what might have been the 
 first indication of the earthquake, but thought there was a noise. The time was ii h 50 m p. m. He did 
 not note the duration. He joined his family and remained a long time in the street with his sons. 
 
 During the earthquake he observed that the movements diminished toward the middle of the 
 shock, but only to be renewed with the same or even greater rapidity. Following the termination of 
 the principal shock there were two very strong ones and innumerable slighter ones up to 5 h a. m., 
 when he went to sleep. 
 
 He observed very frequent flashes of lightning. It was said by some that they proceeded from 
 contacts of electric wires, but they continued after the light had been cut off. 
 
 The furniture of his house did not fall over. The house was built of a wood frame with adobe 
 bricks and corrugated iron roof. It stood on compact gravel formation. Vertical and horizontal 
 cracks appeared in some of the walls. 
 
 (3) Senor Alfredo Clausen, Defensor Publico de la Serena, was in the street walking west¬ 
 ward. He perceived a sound, simultaneous with the first shock. The movements came from every 
 direction. The earthquake was from northwest to southeast. It began more or less exactly at n h 52™ 
 p. m. by the city time and lasted about 4 minutes. He estimated that there were four vibrations per 
 second. The movements varied in character, being rather more brusque than gentle, more rapid 
 than slow. 
 
 Senor Clausen states that between the dates of November 17, 1922, and March 25, 1923, he 
 published a number of articles on the phenomena of earthquakes and their relations to astronomical 
 conjunctions, sunspots and so forth, combating the popular superstitions. Unfortunately, none of 
 these articles, which appeared in El Chilena of La Serena, has been available for examination. 
 
 (4) Senor Luis F. Alfaro Varleta, empleado, residing at Calle Domeyko, No. 1, was seated in 
 his house drinking mate (tea). According to his observation the first indication of the earthquake 
 was the sudden shock itself. It came from below, upward, as proved to his satisfaction by the fact 
 that all the water was thrown out of his wash-basin, without the latter being upset. The time was 
 n h p. m. by his watch and by a clock which stopped at that time. The duration is estimated by 
 some at 6 minutes. 
 
 During the earthquake he four times went down from the second story, in which he and his 
 family lived, and returned upstairs, to carry them out, and when this was done the earthquake was 
 still continuing. Three shocks at intervals of about a minute were experienced. 
 
 All of the glassware on the sideboard was thrown down, as well as vases, etc. The movements 
 were long and brusque. The movements appeared the same in each impulse and seemed to last a 
 minute. 
 
 No damage beyond small cracks was occasioned in his house of adobe brick and wood frame. 
 
 (5) Senorita Maria Lidia Pinto P., a teacher, living at Calle Vicuna 114, had retired, but was 
 still awake. She perceived no indication of the earthquake before the occurrence of the shock, which 
 began violently. It appeared to come from the north. The beginning was at n h 56™ by her watch, 
 official time, and the duration approximately 10 minutes, followed at intervals by after-shocks 
 
 She ran into the patio and thence to the street, where she stayed to observe the heavens. They 
 were lighted by electric flashes, which crossed each other at every repetition of the shocks. She had 
 observed that the sky was clear at g h p. m. when she entered her house, but during the earthquake it 
 was covered with clouds. 
 
 Dishes and glasses fell from the tables, but no furniture was overturned, nor was tbe house 
 damaged. 
 
 The. character of the shocks, especially at first, was very brusque and prolonged. The succeed¬ 
 ing ones were shorter and less violent, but always very sharp. None which occurred that night was 
 gentle. At first they came every 5 or 10 minutes and later every 20 or 30 minutes. The last occurred 
 at 5 h a. m. and those which followed during the day were more gentle and farther apart. 
 
Terremoto of November io, 1922 
 
 31 
 
 (6) A telegrapher, Sehor Bernardo Cortes, D., was in the telegraph office in communication 
 with Valparaiso. He was seated facing south. The first shock came from behind him, from the 
 north, at 23 11 50™ exactly by the office clock. 
 
 The impulses were violent from the beginning. The first were long, rapid and brusque, while 
 the repetitions were of minor intensity and duration. The successive shocks appeared quite distinct, 
 separated by intervals of a minute. There were two of great violence about 2 minutes apart. 
 
 The shocks were not preceded by any noise, but accompanying them were sounds such as would 
 be made by a heavy truck. They came from the north and were the same throughout. 
 
 His house (or office) was built of thick walls of adobe with roof of corrugated iron. It was 
 cracked in straight vertical fissures. Some articles of furniture remained standing, others (mirrors, 
 pictures, lamps and table) were overturned. 
 
 Senor Costa adds the following observations: During the earthquake he observed a sudden 
 change in the sky, which, having been clear and starlit, became overcast, clouded and lighted by light¬ 
 ning flashes from the north. The clouds drove rapidly toward the northeast. For some days prior 
 to the catastrophe the sea had been very tranquil and at a slightly lower level than usual, so that the 
 subsequent change was even more notable. There was a decided change of temperature during the 
 same day (November 10). During several days previous he noted an uneasiness among animals 
 (steers and cows) in the pastures near his house, particularly at night, a condition which made him 
 cautious. 
 
 Residents of Coquimbo 
 
 (1) Senor Eduardo Olivares Quadra, an employe of the post-office, residing in the port of 
 Coquimbo, was standing and at the moment of the shock was reading. He faced north. The first 
 indication of the earthquake was an immense subterranean noise. (Coquimbo is built on a peninsula 
 of solid granite.) The oscillations appeared to be from right to left, as if the shock came from the 
 Cordillera of the Andes. His watch gave the hour as n h 57™ p. m. by telegraph time. The duration 
 was approximately 3 minutes. He aroused and dressed his children. 
 
 There were two principal shocks at an interval of a minute apart. The first was slow (lento), 
 strong (ipero) and longer; the second was short and sharp. The former he estimated to have lasted 
 90 seconds and the latter 30 seconds. 
 
 The sounds accompanying the earthquake had the character of those produced by great rock- 
 falls in a mine. Their direction could not be determined with precision. 
 
 The house, No. 1411 Calle Aldunate, was built of light materials and stood on rock. It sufifered 
 no damage of any consequence. But tables, wardrobe and other articles of furniture were thrown 
 down and overturned from east to west. 
 
 Senor Casandra supplies the following notes: 
 
 The night of the earthquake was one of great calm. There was only a slight breeze from south¬ 
 west, with a suffocating heat. The sky was completely covered with clouds. It was about n h 52 m 
 that a terrifying subterranean noise was heard and was followed in a few seconds by the earthquake, 
 which comprised two strong shocks, proceeding from east to west, while the sky was lighted by 
 lightning flashes. 
 
 About two hours after the earthquake came the maremoto with its three successive waves. 
 The last was the one which did the most damage. It rose to an altitude of 5 meters and attained a 
 distance of 2 km. in the lowest part of the coast. Elsewhere parts of the shore suffered not at 
 all from the wave, indicating that the waters were impelled by strong currents from northwest to 
 southeast. (Coquimbo Bay is a cul-de-sac opening toward the northwest. The wave, passing the 
 wide entrance, was low and did not rise high along the eastern or western shores, but the waters were 
 constricted at the southern end and attained an extreme height of 7 meters above mean level at the 
 railroad wharf—B. W.) 
 
 Residents of Vallenar 
 
 (1) Senor Ivan Franulic, residing at Calle Pratt No. 1274, was standing in his bedroom, 
 awake. He experienced no warning. The shock struck suddenly. He did not observe the direction 
 or the time, but seized his son to escape. He could not open the door. A wall fell, suffocating them 
 with dust. The door opened and he ran out to the street, where it seemed that the earth would open. 
 “ The earthquake was strong enough.” 
 
 There were at least 3 shocks in 4 minutes. They were rapid and sharp. In the house pictures 
 fell and furniture slid, but the mirrors did not fall and windows were not broken. Drawers opened 
 or closed according to position. Those facing south remained closed; those facing north flew open. 
 
32 
 
 Earthquake Conditions in Chile 
 
 (2) Senor Lacarias Rojas Veregara, a tailor, was in the Grand Hotel Vallenar. He was lying 
 down but awake, facing north. He first perceived a noise, which appeared to come from the east. 
 On hearing it he jumped for the key of the door and the shock struck. Grabbing his watch from the 
 bureau, he observed the time to be 1 i h 55“ p. m. He estimated the duration at 3 minutes. Seeking to 
 escape, he fell in jumping from the veranda and landing on all fours remained in that position till the 
 earthquake was over. 
 
 There were three shocks, the first from the east, the second from the south, while in the third 
 it appeared that the earth would fly to the sky. The respective durations of the several shocks was 
 1.5 minutes, 30 seconds, and 1.5 minutes. He could take account of these details, since he had no 
 family in Vallenar. The sound which was like subterranean thunder came from the Cordillera de los 
 Andes, and had lasted 5 seconds when the shock struck. The subterranean sounds continued after the 
 earthquake and resembled waves passing toward the ocean. 
 
 (3) Senor Arsenio Tapia Opuso Molina lived at Calle Pratt No. 1728. He was a merchant and 
 agriculturist and was in his house writing. Although lying down he was awake and somewhat ner¬ 
 vous. He faced north. He did not observe any preliminary indications, but experienced three shocks 
 which seemed to come from the east. He remained in a doorway until the shocks ceased. It seemed 
 as though the house must fall, to judge by the movements (somajeras?) which shook the timbers. 
 The movements were long, rapid and brusque; each one lasted a minute and followed one upon 
 another. There was a sound like thunder, which seemed to come from the coast. His house of adobe 
 with wood frame was rendered uninhabitable, the walls being cracked and thrown out of plumb. 
 
 (4) Senor Guillermo Gray Lopez, of Calle Serrano No. 1357, and engaged in business as insur¬ 
 ance and commercial agent, was in his room about to retire. He first heard an exceedingly strong 
 noise, which seemed to come from below. The hour was almost 12. 
 
 As he ran through the first passageway of his house, which was very narrow, carrying a two- 
 year-old daughter, the eastern wall fell upon him and threw him against the western wall, where he 
 remained buried to the waist. The child was unhurt and was cared for by its mother, who then freed 
 her husband and supported him to the patio. He states that although he was so injured as to be unable 
 to move, he did not lose his sense of direction, in spite of the darkness of the night and the confusion 
 of falling walls. 
 
 The movements were long, rapid and brusque; they came from every direction, some horizon¬ 
 tal, some vertical, and each was of prolonged duration, a minute or more. They were preceded by a 
 very brief interval by a subterranean noise resembling that made by a heavy cart rolling over a 
 pavement. 
 
 His house stood on loose ground. It was built of adobe and wood frame, with some walls of 
 tabique. Two out of three rooms in the western part remained standing, but ruined. The rest of the 
 house was all thrown down except the party walls of adjoining houses. 
 
 (5) Senor Leonio Bardian Ovalle, cashier of the National Bank of Savings, and residing at 
 Calle Pratt No. 1067, was standing at work in his office. He was facing north. He first observed a 
 most powerful noise, followed immediately by the shock. The movement came from left to right, 
 from the ocean toward the Cordillera. The time was n h 46 m by the office clock, which was then 
 stopped. The duration he estimated at 3 or 4 minutes. 
 
 He ran at all speed to his room, where he remained in the protection of the door of his room 
 during the entire earthquake. 
 
 He observed two principal shocks, without any cessation of the vibrations. The movements 
 were all long and brusque. In the stronger ones the ground seemed to jump from above downward, 
 but the dominant movement was from the sea toward the Cordillera. So violent were the oscillations 
 that he was obliged to cling to the door with arms and legs in order not to fall on his face. 
 
 The building had a front and left lateral wall of tabique (wood frame) ; while the back and 
 right lateral w r ere of tapiales. The light walls of tabique remained upright, but the tapiales were 
 thrown down and the roof with them. 
 
 (6) Senor Agustin Banaza was lying down but awake, when he heard a noise like the tearing 
 of cloth. It appeared to come from above. The shock came from west to east, since the walls of the 
 house fell in that direction. The hour was n h 55™ p. m. 
 
 He was unable to remain upright and dragged himself out into the hallway. There were three 
 shocks, of which the second appeared the strongest. The movements were prolonged, rapid, and 
 brusque. Each appeared to last a minute. 
 
 The house consisted of six rooms, of which four were of tabique with adobes, the rest being 
 of adobe walls. The latter fell, but the frame house remained habitable. 
 
 (7) Senor Guillermo Gallo, living at Calle Serrano, corner of Talca, an agriculturist, was lying 
 down in his house, awake, reading and facing east to west. He first perceived a great noise and shock, 
 
Terremoto of November io, 1922 
 
 33 
 
 more or less at n h 50 m p. m. The duration he estimates at about 4 minutes. He at once ran to save 
 his sons, and since he was moving about constantly during the earthquake he does not trust himself 
 to give details. But he is sure the shock came from the sea, moving toward the Cordillera. The 
 furniture was thrown down, including sideboard and wardrobes measuring 1 to 1.20 meters by 2 to 
 2.50 meters. They fell forward from north to south. 
 
 The house consisted of a wood frame of 4 by 4 inch timbers braced diagonally and filled with 
 small adobe brick. It had no rafters and was not wired. Some of the adobe brick fell out, and the 
 plaster fell. Two rooms were crushed by the fall of the adjoining house, built of tapiales and adobe 
 brick, which was a complete ruin. 
 
 (8) Senor Victor Arochas, a traveling salesman, who resided at the Hotel Pardo, was walking 
 in the street. The first shock struck as a single blow from below upward. The time was n h 53^“ 
 and he observed with his watch in hand that it lasted 7 minutes. He struck a light and sought to 
 avoid being knocked down, as the street was very narrow. The shocks were brusque, rapid and 
 distinct, each one lasting 3 seconds, according to his observation. He compares the noise of the earth¬ 
 quake to the breaking of great quantities of glass. 
 
 (9) Senor Rector Miranda Alvarez, of Calle Pratt No. 1490, was asleep in his house adjoining 
 his store, it being his habit to retire early, as he is at pains to state. He lay with his head to the sea 
 and feet toward the Cordillera. He is of the opinion that he woke before the earthquake actually 
 began. He observed a brief noise and immediately after it a great movement of the earth, which 
 appeared to come from the sea toward the Cordillera. The furniture was thrown in that direction. 
 He sprang from bed and ran to place himself in the large doorway which opened into the store. 
 After the first shock he sought his brothers and brought them to the same place. But he observed 
 three distinct shocks, with the following details : After the first sound came a sharp movement which 
 was followed by a calm, as if it were finished, but the movement then recommenced with almost 
 greater force than before. The movements were distinct one from another, their direction being 
 unlike. It did not seem possible to estimate the lengths of the shocks, but he would judge that they 
 lasted several seconds. 
 
 (10) Senor Eduardo Wolf, a builder, living at Serrano, corner of Colchagua, was asleep in a 
 “ chalet ” on Calle Serrano, lying with his face toward the east. He first perceived a violent shock. 
 The oscillations appeared to come from all directions. He could not say in what direction the earth¬ 
 quake advanced, other than that it moved from east to west. By his watch it began at n h 45™ p. m., 
 and lasted 5 minutes, more or less. He dressed himself, it being impossible for him to get out in the 
 darkness. His cot having been overturned, he could not find the door. He repeats that the first shock 
 was long and very violent, the others, which he could not count, were shorter and less violent. 
 
 Senor Wolf adds the following information regarding the ground under Vallenar, basing his 
 statements on his experience as a builder. Between the plaza and the upper part of the city, as well 
 as between Calle Merced and the river, the formation is gravel, which is on the average 2 meters deep. 
 It rests 011 clean sand. North of Calle Merced and up to the north embankment (of the terrace) the 
 gravel is but 1 meter deep and rests upon hardpan (or mud?) (“ fango”). From the plaza to the 
 station, the hardpan? (fango) is met at shallow depth and consequently there is water at a depth of 
 a meter. All the houses of Vallenar tremble when an automobile or cart passes. He is therefore of 
 the opinion that the subsoil is quicksand or fango throughout. 
 
 Residents of Freirina 
 
 (1) The cure of Freirina, Padre Felix Morey Amengual, was in his house, lying down but 
 awake. He faced south. The first indication was a sharp blow like that of a bomb exploded beneath 
 the earth. It came from below upward. Following the first blow there came oscillations of great 
 rapidity, at first from the sea toward the Cordillera (west to east) and afterward from north to 
 south. The hour was 2 minutes before 12 by his watch. The destructive shock lasted half a minute. 
 He was unable to go out by any of the doors and finally escaped by a hole between the roof and the 
 fallen walls. 
 
 He did not clearly recall the number of shocks, but would say that there were three or four 
 destructive ones and afterward many strong ones which followed each other very rapidly, during 
 the night and following day. The first movements were extremely rapid and brusque. The others 
 were not equally so, but nevertheless were rapid and sharp. He states: “ I do not feel able to define 
 the duration of the individual shocks, but in my judgment during the 24 hours following, the earth 
 did not cease to oscillate, although imperceptibly, the heavier shocks succeeding each other at irregu¬ 
 lar intervals.” No sound of any kind accompanied the first shock, which felt like an explosion. The 
 following shocks produced a noise, which was amazing and terrifying. They all came like explosions. 
 
34 
 
 Earthquake Conditions in Chile 
 
 His house of tapiales, surmounted by adobe bricks, standing on gravel and boulders, consisted 
 of two wings. The north-south one fell, whereas the east-west one did not. But all the walls were 
 cracked or thrown out of plumb. 
 
 Residents of Huasco 
 
 (1) Francisco Quinones Gorman was asleep in his house in Huasco with his face toward the 
 coast. He perceived no preliminary indication of the terremoto, which struck suddenly. It appeared 
 to him to come from northwest, and lasted several minutes. The hour was n h 55™. He remained in 
 bed, hoping it would pass, but on learning of the rise of the sea he fled. The first shock was long 
 and strong. The succeeding ones were short, but still strong and rapid. They lasted 10 seconds more 
 or less. The sound began simultaneously with the temblor. It sounded like thunder. 
 
 His house was built on solid rock of wood frame and roof of galvanized iron. A part of the 
 plaster fell. A jar, full of “ loza,” fell to the floor and rolled about. 
 
 (2) Senor Pedro 2d Ruiz was in his house, sleeping with his face to the west. He experienced 
 a strong shock which appeared to come from in front. The terremoto advanced from south and 
 west, to judge by the falling of objects, which was in the opposite direction. The duration was 
 10 minutes. The hour was 23 11 50™, official telegraph time of Vallenar. 
 
 He gathered his family in the passage of his house, preventing their running out, while he 
 looked for matches, lighted a candle, and they dressed themselves. 
 
 There appeared to be three principal shocks, at very short intervals, but it shook continuously. 
 The shocks were long, rapid and brusque, each lasting approximately 3 minutes. Having been asleep, 
 he recognized only the terrible noise that accompanied the terremoto. 
 
 The articles of furniture overthrown were a center table, wardrobe and “ veladores.” They 
 fell in part to the north and in part toward the west. This statement applied also to the walls of the 
 enclosure. 
 
 Residents of Caldera 
 
 (1) Senor Enrique E. Ramirez, an official, was asleep in his house, facing north. He first per¬ 
 ceived a great noise, which appeared to come from in front of him, whereas he states that the earth¬ 
 quake came from the south. The hour was n h 45 ra p. m. and the duration was 7 minutes. He ran 
 into the street with his little children. He did not distinguish separate shocks, but observed an equality 
 in noise and vibration throughout. 
 
 He adds the following information regarding the maremoto: The first rise of the sea occurred 
 about I2 h 30 m . The greatest wave advanced between 2 h and 3™ a. m. of November 11. At Ramadas 
 Point the advance amounted to 600 meters and to 125 meters along the harbor front. The customs 
 house, railway station and other buildings were destroyed or moved. 
 
 (2) Senor Jorge L. Becerra, Alcaide de Aduana, was asleep in his house facing north. He was 
 awakened by a strong noise, which came from the north, from the right, from below upward in 
 front. The terremoto also appears to him to have come from the north. The hour was n h 50 1 " 
 according to his watch, which kept good time. The duration he estimates at three-quarters of an 
 hour of constant trembling. He got up and ran to the playa to see the maremoto, which destroyed 
 the customs house and other buildings. (It is difficult to reconcile this apparently immediate action 
 with the times given in the preceding account.) 
 
 (3) Senor Bernado Tornini, a merchant, was on board the steamer Flora, anchored in the bay. 
 He was sitting in the cabin with friends, looking toward the north. He first heard the sound, which 
 began about n h 50™. The duration was about 5 minutes. Of the group, which included the captain 
 of the vessel and the harbor master, together with several others, Senor Tornini was the first to give 
 the alarm. They went on to the deck and walked from stern to prow. They observed many lightning 
 flashes, some of which seemed to fall on the poop of the steamer in a terrifying manner. On going 
 ashore they encountered a warm rain, which began to fall about half an hour after the beginning of 
 the terremoto. The sea rose several times, but without surf, and at its greatest advance attained a 
 height of 6 meters above the highest tide. 
 
 (4) Senor Guillermo W. Lavan Rives was on board the steamer Flora, anchored in the bay. 
 He was standing facing east. There was a noise which he took to be that of the winches of the 
 steamer. He went ashore, and 15 minutes after the beginning of the terremoto he observed close at 
 hand the initial rise of the maremoto, being at the time in the boat in which they came from the ship. 
 While we were still at a short distance from the passenger pier the sea had begun its first slow rise. 
 When the landing-steps were reached they could not use them, because the boat was on a level with 
 the flooring of the dock. This first rise attained a height of 5 meters, more or less, above high tide. 
 
Terremoto of November io, 1922 
 
 35 
 
 The several advances of the sea which followed were greater than the first, but always gradual. 
 The maximum attained 7 meters above the normal stage and advanced 35 meters more or less, doing 
 much damage. It occurred about 3 U 30 111 a. m. 
 
 (5) Senora Ana S. de Baez, Administrador de Correos Telegrafos, was walking in the street 
 and did not perceive any indication before the earthquake, which began at n h 48" 1 by the official time 
 of the state telegraphs. 
 
 After the earthquake the sea remained completely tranquil, that is, without waves, but after 
 30 minutes began to advance. It rose without noise and without surf. Between I2 h 30™ a. m. of 
 November 11 and g h a. m. of the same day the sea advanced many times, each advance lasting 20 
 minutes, more or less. 
 
 According to approximate estimates, the greatest advance was 50 meters in the higher parts 
 of the port and 100 meters in the lower part. The level reached by water is estimated at 5 meters 
 above the level of the sea. The greatest occurred between 2 11 and 4"* a. m. 
 
 These data la Senora Baez submits as in accord with the facts, while admitting that there may 
 be some errors, since it was impossible to observe and estimate in all its magnitude a phenomenon so 
 unfamiliar to the experience of those living on the spot. 
 
 Residents of Chanaral 
 
 (1) Senor Guillermo Zepeda was in his house on Calle San Martin, Chanaral, sitting, looking 
 toward the northwest. He observed a subterranean sound accompanied by a sudden, brusque shock. 
 It came from behind him. The oscillations were from the sea toward the Cordillera. The shock 
 began at u h 50 m . It lasted 3 minutes with maximum intensity, and continued during half an hour of 
 minor oscillations. He rose to his feet and would have run, but the movements of the ground made 
 it difficult even to stand. 
 
 There were about three principal shocks at intervals of 2 minutes. The movements were long, 
 rapid, gentle (suaves) and regular. During and after the terremoto, when the sea rose, people 
 observed a kind of roar in the bay, which led them to think a volcano might be in eruption. The 
 noise of the terremoto began with the first shock and resembled the noise that accompanied the 
 maremoto. Although very much louder, it resembled that of heavy surf. The day following the 
 earthquake it was observed that the sea had withdrawn, leaving a great extent of the playa uncovered. 
 
 (2) Senora Maria Isable T. Zeballos, Director of Primary Instruction, was asleep facing the 
 south. The shock itself was the first indication she perceived. It appeared to come from the east, 
 from her left, because on rising to her feet she leaned to that side. The earthquake was not alarm¬ 
 ing. She partly dressed and went into another room. The maremoto began an hour after the shock 
 and continued about 4 hours. The sea advanced three times. It rose 9 meters, destroyed 14 blocks 
 of houses, and swept 4 blocks inland. The movements were gentle, but prolonged. The sound 
 preceded the shock and resembled that of a heavy cart. She did not notice any variations of the 
 movements. 
 
 (3) Senor Oswald Fernie, engineer, though lying down was awake. The first indication was 
 the sound, which came from the south. The terremoto began, more or less, at 12 o’clock and con¬ 
 tinued 3 minutes. He remained a minute in bed and the rest of the time in his room. He observed 
 the movements to be almost continuous and slow and gentle. 
 
 Residents of Copiapo 
 
 (T) Professor Carlos A. Gonzales H., residing at Chanarcillo 1010, was sitting in his house 
 facing northwest. He first perceived a loud noise like thunder from the northwest. He judged, by 
 the direction in which the walls fell, that the earthquake came from the northwest. The hour was 
 n h 55 m by his watch, which he had set that same day with the railroad time. He was unable to esti¬ 
 mate the duration. He went out into the street with his family, not running, but pausing long enough 
 to sense the oscillations and seek a safe place. There were three shocks at brief intervals. The first 
 was prolonged, rapid, but gentle; the second was sharp. They were distinct and lasted during 
 minutes. 
 
 (2) Senor Luis A. Romo Ch., Intendente of Atacama, was in his bedroom, lying down, but 
 awake. The first indication of the earthquake was a subterranean noise of great intensity. It came 
 from the south and very soon from underneath. The earthquake came from the south, as was demon¬ 
 strated by telegraphic advices. It occurred at 23 1 ' 55™, by a good watch compared with the telegraph 
 time. The duration was about 4 minutes by his watch. He remained in bed during part of the move¬ 
 ment and then went out into the patio and remained standing, holding on to a tree to avoid falling. 
 
 4 
 
36 
 
 Earthquake Conditions in Chile 
 
 He observed two shocks, a first and afterward a second, which was more violent and caused him to 
 leave his bed. The movements he describes as prolonged, almost continuous, rapid and brusque. The 
 movement was indeed almost equal. It was an earthquake of great intensity throughout. The sound 
 was heard first. It suggested the rolling of a cart or of many carts of enormous weight, coming from 
 the south ; subsequently the shaking and groaning of the structure, as well as of the door and windows 
 did not permit the earthquake sound to be heard. The furniture fell and danced. It comprised ward¬ 
 robes, stands (estantes), and an iron safe, which measured 70 cm. Most of them fell toward the 
 west. The house was a wood frame with cana de Guayaquil, the roof of wood and galvanized iron. 
 Some of the timbers were broken, the frames were partly wrenched apart, and most of the plaster 
 and ceilings fell. Nearly all of the adobe wall surrounding the inclosure fell. 
 
 (3) Senor Federico Melendez M., of Calle Infante 551, was at Calle Rodriquez 440; had just 
 gone to bed and was reading. He faced northwest. The first indications were a noise and small 
 shock which lasted a second. He thought it came from in front; that is, from the northwest. In his 
 haste to save his children he took no note of the direction of the movement or of the time. He put 
 on his trousers and succeeded in finding his shoes, but dropped them to pick up a child asleep near 
 him. Having opened the door, he remained standing in it and did not run out because the child was 
 
 naked. His wife did not stop for clothes, but gathered up the baby and little boy and ran toward the 
 inner patio. As he sought to follow her the door on the northeast (No. 1) side of the room slammed 
 in his face, while that on the northwest (No. 2) opened. By it he ran into the hallway and so to the 
 street. Senor Melendez gives details of the displacements of furniture as shown here: 
 
 He thinks that after the first swinging shock there was a single one, whose vibrations were 
 intense and were maintained possibly for 5 minutes. It appeared to him that the movements began 
 from northwest to southeast and afterward developed in all directions, with dominant brusqueness 
 in the initial direction. He observed that the waves were long and well defined, momentarily inter¬ 
 rupted or cut off, producing very notable horizontal shocks due to inertia in a northwest to southeast 
 direction. 
 
 His house stood on comparatively firm ground (compact gravel and cobbles of a coarse alluvial 
 fan) near the base of the mountain (east of the city). It was built of wood frame with cane (cana 
 de Guayaquil). It suffered no other damage than that of cracks above the doors and windows. 
 
 (4) Senor Manuel Corona, F., agent of the Sociedad de Minas i Fundacion de Carrizal, was 
 sitting in his house at Calle Infante 1060, facing north, under an electric light. The earthquake was 
 initiated by a great noise and shock almost simultaneously. He could not state the direction. The 
 hour was n h 50“, at exactly which time there stopped a large pendulum clock that was kept on rail¬ 
 road time. He did not note the duration, but could estimate that the strong movement lasted 4 
 minutes. He left his room to go out on to a porch, turning on the electric light, but it was quickly 
 
Terremoto of November io, 1922 
 
 37 
 
 cut off. As the movement continued to increase he ran out toward a tree and held on to it, since he 
 had difficulty in remaining erect. The motion began to decline, but as it still continued he ran into 
 the open toward the hill, but did not go on, as the shocks had greatly diminished. He is unable to 
 describe separate shocks. The movements appeared long and not very brusque. A stand (estante) 
 and bureau were thrown down and nearly all articles were moved out of their places. 
 
 His house stood on cultivated ground and was of wood frame with cane (cana de Guayaquil). 
 It suffered no damage except loss of plaster and stucco and the breaking of some beams, which were 
 in poor condition. 
 
 (5) Senor Luis G. Brand, C., Professor del Liceo de Hombres, was in the Liceo lying down 
 but awake, and facing southeast. He first noticed a strong noise, but did not observe its direction. 
 He judged that the earthquake came from southwest toward northeast by the movement and the 
 noise of the windows. The hour was 23 h 46 m , by Santiago time. He estimates the duration at 
 4 minutes. He went out into the patio and there awaited the termination of the shocks. 
 
 In addition to that which he designates the terremoto itself, he noted a second and a third 
 temblor with intervals of 4 and 2 minutes. The movements were long, rapid, and brusque. The 
 shocks were distinctly separated. He observed the sound which preceded the shock. It resembled 
 that made by a heavy cart. 
 
 The building stands on firm ground (compact gravel and boulders) and consists of wood 
 frame with cana de Guayaquil. The ceiling was cracked and part of it fell. 
 
 (6) Senor Jose Escanriaza, chief of the third telegraph district, was walking in the street 
 facing northwest. He first perceived a loud subterranean noise, followed by a temblor of moderate 
 intensity (“regular intensidad ”)• It came from the south, according to telegraphic reports from 
 Vallenar. He had no watch at hand. He ran to avoid being crushed by falling walls. There were 
 two shocks, the first of moderate intensity, but increasing in violence almost immediately. The sound 
 resembled that of a heavy cart. 
 
 (7) Senor Ladislav A. Arestizabal, an apothecary residing at Calle Carrevas 708, was in his 
 house, asleep. He was awakened by a great movement accompanied by much noise. He is unable to 
 say from what direction it came. The hour was 23 11 50™, more or less, and the duration 6 minutes, 
 by his estimate. He started to dress, but to save his child he was obliged to desist. Naked he ran to 
 the balcony and jumped into the street. He received the child from his wife, whom he assisted to 
 descend, and they ran to the plaza for safety. After the first shock, he felt many others, at intervals 
 which he could not estimate. There was a great deal of noise, in part like thunder with detonations. 
 Immediately on going into the street he observed a light in the north, the heavens being rosy. The 
 stars appeared to tremble. The movements which followed the principal shock were of long dura¬ 
 tion, at least some of them, but of almost uniform intensity, like the swinging of a hammock. The 
 barking of dogs increased the sense of tragedy in the situation. There were times when one sensed 
 only the great noise, without movements that could be perceived without instruments. 
 
 (8) Senor Felix P. Olea, an attorney and notary public, living at Atacama No. 545, was 
 seated in his bedroom looking toward the south. He first perceived a noise which appeared to come 
 from in front to the right and from below. The hour was n h 50 m by his watch. The duration he 
 estimates at 6 minutes. Pie jumped to his feet to prevent his wife and child from running out, as he 
 had great confidence in the construction of the house. The movements were many and very con¬ 
 tinuous. They were long, especially the first, and repeated many times; some were rapid and sharp; 
 some of those which succeeded the first occupied more than half a minute. The sound preceded the 
 first shock by about 10 seconds. It resembled that of an automobile and appeared to come from the 
 southwest. All of the furniture was overturned in the house, which stood on cemented gravel. It 
 was of wood without plaster, except two interior rooms which had mud roofs; they fell in. 
 
 (9) Senor Aristides G. G. Zoraguin, professor in the School of Mines, was sleeping lightly 
 in his house at Avenida Juan Martinez No. 128. The first indication was a noise like distant carts, 
 followed in a few seconds by the movement. It appeared to come from the west, judging by the dis¬ 
 placement of the furniture. The piano, wardrobes and other heavy furniture marched from east to 
 west and reached the middle of the rooms. The hour was n h 47 m by railroad time. The duration 
 was perhaps 4 minutes. He remained standing in the middle of the street watching the oscillations 
 of the building from south to north and the wave-like movement of the earth. There were three 
 principal shocks, the last being the most violent. They were rapid and brusque. 
 
 The house was of wood frame, filled in with small adobe brick. The section which consisted 
 of these materials, with wire inside and out, suffered no damage whatever. The same was true of a 
 part which consisted of a wood frame filled in with brea (brush) ; but in another part where the 
 walls were filled with adobes, the frames separated at the corners. The suburb in which his house is 
 
38 
 
 Earthquake Conditions in Chile 
 
 situated is near the mountain and it is noteworthy that not a single house in it was thrown down, 
 although some of them were of poor construction. Yet they were not damaged in the least. 
 
 (10) Senor Oscar Letchier, La., apothecary, living at Calle Atacuna 477, was lying awake in 
 his house, when he perceived a strong shock. It appeared to come from all directions. The hour was 
 ii h 55 m more or less. The duration was about 10 minutes, as he would estimate. He carried his 
 youngest son down stairs and returned for his wife and other children, who had remained, as it were, 
 paralyzed. He recognized three shocks, almost without intervals of quiet. The movements were long 
 and rapid, very brusque, unlike any he had previously experienced, and lasted three minutes more 
 or less. The sound began at the same time as the shocks and resembled the discharge of heavy artil¬ 
 lery. The noise was so great that his voice, which he describes as somewhat powerful, could not be 
 heard 3 meters away. 
 
 (11) Professor Pedro Villagran Arrayo, living at Rodriquez, corner of Vallejo, was standing 
 in his house facing southeast. He first perceived a loud subterranean noise, which came from the 
 southwest. The time was n h 50™ by his watch. The duration was 10 minutes by his estimate. While 
 his wife opened the doors to allow the children to escape to the street, he ran to one who was still 
 sleeping. They then fled to a crossing of two streets, where they remained during the rest of the 
 earthquake. He did not observe the number of shocks. The terremoto began with a rapid movement, 
 which demonstrated the great danger. After about 3 minutes it became very violent and irregular. 
 The earth rocked in every direction. After about 5 minutes it returned to its initial period with 
 regard to the intensity. Very soon after the earthquake began the city lights failed, leaving every¬ 
 thing in complete darkness. On entering the street one observed great lightning flashes in the south¬ 
 east, which illuminated the tragic obscurity. That lasted a few moments. Shortly after the terremoto 
 had ceased the atmosphere began to undergo a complete change. From having been clear it became 
 humid and cold and 2 or 3 hours afterward began to drizzle. 
 
 (12) Senor Samuel Jenkins, an agriculturist and miner living at Calle Colipe 475, was lying 
 asleep in his house, when he was roused by a loud and very violent noise. He faced south and it 
 appeared to come from the right, that is from the coast. The hour was n h 50™ p. m. The terremoto 
 lasted during 2 minutes of great violence and 5 minutes of less intensity. He remained in his room. 
 There were two shocks at intervals of a minute, more or less. He noted both horizontal and vertical 
 shocks, in alternation, the same being very hard. The noise at first resembled thunder and then became 
 confused with that of shattering windows and falling roofs. 
 
 Residents of Tierra Amarilla 
 
 (1) The Secretario Municipal of Tierra Amarilla, Senor Juan 2d Echeverria, was sitting in 
 his house facing the west and first perceived a great noise, together with a very brusque movement, 
 which came from in front of him. The hour was n h 55 m and the strong movement lasted 2 or 3 
 minutes. He ran out into the street and went ahead to avoid falling. He and a friend helped each 
 other to stand by holding hands. He estimates the number of shocks at five or six of high intensity 
 at intervals of quarter of an hour apart. They were long, rapid and brusque. The shocks which 
 followed the great temblor were quite distinct from it. The noise at first resembled that of a train. 
 During the succeeding shocks it suggested a heavy cart rolling over hollow ground. Some articles 
 of furniture were thrown down and fell toward the east. The house of wood frame filled in with 
 brush and mud plaster was not cracked. Some cracks appeared in the roof of mud and rushes. 
 
 Senor Echeverria further observed that the railroad was damaged by the caving of fills. 
 Pendulum clocks were stopped. Pictures and other hanging objects banged against the wall. Windows 
 were broken. There were electric discharges, and in the mines some timbered stopes caved in. 
 
 Residents of Puquios 
 
 (1) At Puquios, the most eastern point from which the questionnaire was returned, Senor 
 Arthur C. Cahera, a mining engineer, was sitting in the house of a friend when the terremoto began. 
 It came from the south according to the way it felt. The hour was n h 55 m , official time. The dura¬ 
 tion was 3 minutes. He took the time. During the movements he went out into the street and took a 
 “ pimiento.” He felt four shocks separated by distinct intervals, the length of which he did not 
 observe. The movements were long and rapid, not to say brusque. They were distinct and the last 
 was from below upward. Each one lasted 45 seconds by his estimate. A noise began simultaneously 
 with the shock. It resembled surf. It seemed to come from the east. Furniture did not fall over, 
 but was moved out to the middle of the room. The house stood on compact gravel and sand. The 
 house, consisting of wood frame with walls of cana de Guayaquil and adobe, was wrenched at the 
 corners. The wall of adobes surrounding the inclosure was damaged throughout its extent. 
 
Terremoto of November io, 1922 
 
 39 
 
 Residents of Salado 
 
 (1) At the railroad station Estacion de Salado, situated 35 km. inland from the coast, the 
 station master, Senor Carlos J. Duarte, was in his room lying south to north and awake. He heard 
 a sound like a locomotive approaching rapidly from the west; that is, from the coast. At the same 
 time he seemed to hear the sea breaking close at hand. The hour was n h 55"* by railroad time, and 
 the duration was more than 5 minutes. He observed that the sky was lighted as by the moon for 
 the space of 5 minutes, after which darkness set in again. There were many shocks, which continued 
 until 7 h a. m. next day. A sideboard and shelves were overturned toward the west. No damage was 
 done to the station, which was built of wood and roofed with galvanized iron. 
 
 Residents of Potrerillos 
 
 ( j ) Senor Hernando Osandon D., a chemist, was in the mining camp of the Andes Copper 
 Company. He was about to fall asleep, when he experienced a severe earthquake shock. It was 
 6 minutes before 12 by his watch, which was set by the mining time and presumably by that of the 
 railroad. The terremoto lasted about 5 minutes. Awakened, he lighted a candle, looked at his watch, 
 got up, and opening the window looked out. He then went to bed and followed the movements of 
 the ground. There were possibly three shocks at equal intervals, but the movement appeared con¬ 
 tinuous, except that a fresh impulse was given three different times. He states that he did not sup¬ 
 pose there was any sound except the earthquake, but what there was resembled the rolling of a heavy 
 cart a long way off. It appeared to come from the east. 
 
 (2) Senor Hennogenes Pizarro A., was at Agua Helada, a camp northeast of the mining 
 camp of Potrerillos, about 4,000 meters above sea. This is the highest point and the farthest north¬ 
 east from which any information has been received. Pie was asleep facing east and was awakened 
 by the movement of the ground. The shock came from southwest and moved northeast, at n h 50“ 
 p. m. Potrerillos time. He did not observe the duration. He went out and stood on a point of rock 
 nearby. There were two shocks about 20 seconds apart. The second one was much the more intense. 
 Cups fell from the shelves toward the northwest, the shelves themselves extending southeast to north¬ 
 west. The movements were horizontal from southwest to northeast. They were slow and gentle. 
 The intensity was almost constant during the first 30 seconds and then increased. Each movement 
 lasted about 30 seconds. He did not perceive any sound. 
 
 EFFECTS ON MONUMENTS 
 
 In the city of Copiapo there were three monuments which were notably damaged 
 by the terremoto. They all stood on the Alameda, a street running from firm granite 
 down an alluvial cone of coarse cobbles and sand to the river, and consequently dif¬ 
 fering in the character of the foundation material. The first of the monuments, 
 dedicated to O’Higgins, stood nearest the hill on the firmest ground. It was a marble 
 shaft standing on a pedestal and it remained intact, but was rotated at the joint of 
 the pedestal and shaft through an angle of 3 0 . The bottom moved from left to right, 
 anti-clockwise with reference to the top section. 
 
 The Matti monument, erected in honor of a local citizen, consisted of a bronze 
 statue on a lofty stone pedestal. The statue fell toward the river, because the actual 
 base on which it stood consisted of two stone slabs, and the one on that side gave way 
 when the shock threw the weight of the bronze upon it. The violence of the vibration 
 that enabled the shock to tilt the bronze may be attributed to the character of the soil, 
 which was soft, this statue being nearer the river than either of the other two. 
 
 P>etween the O’Higgins and Matti monuments stood a more pretentious struc¬ 
 ture dedicated to Atacama. The pedestal was 12.6 feet (3.85 meters) high and was 
 surmounted by a bronze figure 9.5 feet (2.9 meters) tall. The pedestal consisted of 
 several sections. At the base was a wide concrete block representing four steps; it 
 was followed by a segment built up of four tiers of brick, laid in weak mortar; and 
 
40 
 
 Earthquake Conditions in Chile 
 
 upon this came a concrete structure, said to he hollow and modeled with appropriate 
 offsets. Between the pedestal proper and the bronze there was interposed a thin con¬ 
 crete slab, which was not seen from below, but which, as it was not fastened in place, 
 formed a loose segment between the pedestal and the statue. 
 
 The most obvious effect of the earthquake was to throw the statue in such a way 
 that it came to lie with its foot about 21 feet (6.5 meters) from the center of the 
 monument and its head toward the latter (e in Fig. 5). It was evidently thrown with 
 violence and its path was apparently such as would be communicated to it by rotation 
 of the pedestal in a clockwise direction. 
 
 The pedestal of the Atacama monument showed abundant effects of rotation. 
 The bricks between the two masses of concrete were crushed, rounded and displaced 
 
 as if the base had twisted about under the superincumbent weight and the shearing- 
 had been concentrated at the weak joint. Upon ascending to the top it was found 
 that the thin slab upon which the statue had stood was twisted about on the next 
 lower section and yet was nearly parallel with the steps of the base. It seemed as 
 though the inertia of the statue had held the thin slab steady while the entire 
 pedestal turned clockwise under it. This movement threw the statue. The slab 
 appears thereafter to have remained fixed on the pedestal which stood still, while the 
 base turned under the brickwork in an anti-clockwise movement. This may have been 
 the case, but it can not be demonstrated, for the sides of the different sections were not 
 originally parallel and it is impossible to reconstruct their positions before the rota¬ 
 tion occurred. 
 
Terremoto of November io, 1922 
 
 41 
 
 This conclusion follows from the observations of compass courses on the sev¬ 
 eral sections on all four sides, which are given below. 
 
 Section 
 
 North side 
 
 East side 
 
 South side 
 
 West side 
 
 Loose slab .^. 
 
 N. 26° E. 
 
 N. 64° W. 
 
 N. 25 0 E. 
 
 N. 65° W. 
 
 Top of concrete. 
 
 Brick section . 
 
 N. 40° E. 
 Crushed 
 
 N. 56° W. 
 
 N. 34 ° E. 
 
 N. 58° W. 
 
 Top step . 
 
 N. 33° E. 
 
 N. 64° W. 
 
 N. 32° E. 
 
 N. 58° W. 
 
 i Lowest step . 
 
 N. 38° E. 
 
 - 
 
 N. 6o° W. 
 
 N. 30° E. 
 
 N. 55 ° W. 
 
 The above courses are plotted in figure 3 and suffice to show that the Atacama 
 monument when originally constructed had no two sides parallel, nor any right 
 angle. What the original positions were or how much the parts may have rotated 
 with reference to each other is therefore indeterminable. It follows none the less 
 from the throwing of the statue and the crushing of the brick that a rotary move¬ 
 ment was communicated to the structure. 
 
 SURFACE EVIDENCES OF FAULTING 
 
 Experience in California in tracing active faults leads to the expectation that 
 similar faults in other countries may be identified by fissures, landslides, ponds, and 
 valleys, which range along the outcrop in a line. As has already been stated, the 
 search for such evidences in Atacama was practically vain and the failure to find 
 them led to the conclusion that the mechanism of faulting differed in some impor¬ 
 tant particulars from that which has been recognized in California. 
 
 The inquiry for fissures was included in the questionnaire that was widely 
 distributed, and many of the responses cite instances of their occurrence. But in 
 every case it is demonstrated by the evidence of the location or was found on exami¬ 
 nation that the cracks which were described were produced by superficial landslides 
 and were controlled by the slope of the basement-rock surface beneath the alluvium. 
 The fissures of this type were not connected with earthquake faults. 
 
 Two occurrences were found, however, which appear to have had more deep- 
 seated relations. Both occurred near Vallenar, in the region of highest intensity, one 
 being at the mouth of the Quebrada Jilguero, the other in the bluffs of the Arroyo 
 Valparaiso. 
 
 Quebrada Jilguero 
 
 The Quebrada Jilguero enters the Rio Huasco about 3 miles (5 km.) east of Val¬ 
 lenar from the northeast. It is characterized by the peculiar feature of a narrow 
 canyon in hard rock, through which the Jilguero runs in the last few hundred yards 
 before joining the main stream. Its valley above the canyon is wider and lies between 
 high banks of gravel.. The facts are, perhaps, best explained by considering the Huasco 
 and the lower section of the Jilguero as superimposed on the firm rock by the gravels 
 
42 
 
 Earthquake Conditions in Chile 
 
 that formerly filled the entire valley. The streams meandering over the aggraded 
 surface assumed their present courses and were hung up on a spur of hard rock, in 
 which they have cut their actual channels. 
 
 The rock on the western side of the Jilguero canyon, which is about 150 feet 
 (45 meters) high, was riven from bottom to top by a movement which is reasonably 
 attributable to the earthquake. It was broken and spalls, which showed fresh frac¬ 
 tures, fell from the cliff. The crack itself, however, did not show any displacement. 
 The two sides appeared to fit, practically as before. It was traceable only by freshly 
 broken surfaces and by the opening of old joints, which it traversed. Its strike was 
 north 45 0 east, magnetic, and the dip was 6o° northwest. (See photograph, Plate 
 XXII B.) 
 
 Valparaiso Slide 
 
 The Arroyo Valparaiso enters the Huasco about 2 miles (3 km.) east of Vallenar 
 by a valley cut in the gravel formation. The latter is somewhat firmly cemented and 
 stands at a steep angle of rest, but the valley is none the less wider than others like it, 
 and there is a narrow bottom-land along the stream. The bluff on the east rises 165 
 feet (50 meters) above the brook and in its upper part exhibits a distinct fault scarp, 
 below which there are masses of the gravel that have slid down. (Plates XXII- 
 XXVI.) 
 
 The scarp is 42 feet (13 meters) high. It is straight in a north 35 0 east mag¬ 
 netic direction and dips 75 0 west toward the valley. In these respects it conforms to 
 what would be expected in an ordinary landslide. But the surface is hard, when 
 scratched with a knife, and exhibits striations that dip 55 0 from the horizontal, down¬ 
 ward toward the north. These details appear to distinguish it as a shearing plane on 
 which there has been compression. If so, it is older than the erosion of the valley, 
 since the shear could not have developed except in a continuous mass of gravels. 
 
 The slide below the scarp is a large body of the gravel formation, which shows 
 transverse fractures and displacements in a gravitative direction, downstream. Their 
 positions can best be appreciated by inspection of the photographs. They were fresh 
 fractures and demonstrated notable movements in the recent shock, but the slide as 
 a whole is much older. It originated in some much earlier earthquake and has been 
 repeatedly shaken, as is evident in the contrast of weather slopes and fresh fractures. 
 
 The scarp may reasonably be regarded as a fault scarp, the outcrop of a deep- 
 seated compression fault which here traverses the gravel deposits. Definite proof of 
 the extension of the fault plane into the rocks is, however, lacking, as they are not 
 uncovered. 
 
 DISTRIBUTION OF INTENSITIES 
 
 It is generally assumed that a study of the apparent intensities of an earthquake 
 shock, as indicated by the degree of damage suffered at various points within the area 
 of vigorous activity, will define a central tract of maximum effect, surrounded by 
 zones of less and less vigorous action, diminishing outward. The central tract is 
 
Lip^ry 
 Of THE 
 
 UNIVERSITY OF ILLINOIS 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate VII 
 
 A. Copiapo. Adobe wall of large building intact, tied with timbers; tapiales thrown down. 
 
 temporary shelter of rushes. 
 
 B. Tatara. Estancia west of Vallenar. near fault line; adobe buildings wrecked. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate VIII 
 
 
 
 
 
 pjs@" 
 
 »*' 
 
 - . T' — 
 
 .** s*\.~ 
 
 I -. 
 
 B 
 
 
 4 - - 
 
 ■ , 4 . ’ •<' 
 
 A and B. Vallenar (12.5 miles (20 km.) southwest of). Examples of effect of the earthquake 
 upon massive structures of dry stone walls ; located on gravel plain above fault. 
 
Carnegie Inst. Wash. Pub. 382 
 
 (Willis) 
 
 Plate IX 
 
 Vallenar. Church tower intact. B. Vallenar. Walls of church, showing columns and 
 
 walls of cana de Guayaquil on frame construction. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate X 
 
 . Copiapo Church in Plaza Godoy. Frame structure, B. Smelter chimneys at Huasco. Note twisting effect 
 
 interior walls and plaster crushed. a t node of vibration. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XI 
 
 A. Copiapo. Destruction of tombs of massive masonry. 
 
 B. Vallenar. Ruins after the removal of the dead and wounded, victims of ignorance 
 and carelessness, who numbered 1,300, nearly one-third of the population. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XII 
 
 - ■m w mnwm ' m i f* y .; , y 
 
 
 vmmtm 1 
 
 $Spw 
 
 *;.. — v; 
 
 It ff—* ■ " !£ 
 
 T^rr 
 
 m jrryr 
 
 B. Average construction of frame, cana de Guayaquil, and 
 adobe; to be plastered with mud. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XIII 
 
 B. Upper Huasco valley, La Pampa. Very old adobe house with mud roof. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XIV 
 
 A. Vallenar. Wall of tapiales; two high, partly thrown. 
 
 B. Vallenar. Typical ruin of adobe house with heavy mud-covered roof; front wall pushed 
 
 out by rafters. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) Plate XV 
 
 A. Upper Copiapo valley, San Antonio. Looking northwest, showing general destruction of 
 
 adobe houses. 
 
 B. Upper Copiapo valley, San Antonio. Looking southwest, showing general ruin and a new 
 
 wall of tapiales. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XVI 
 
 A. Upper Copiapo valley, San Antonio. Cemetery walls standing on east, west, and south, on 
 gravel cone inside canyon; white rhyolite dike in Jurassic sandstone. 
 
 R. Upper Copiapo valley, San Antonio. View up valley, showing broad, marshy fill on which 
 
 village stands. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XVII 
 
 A. 
 
 Upper Copiapo valley, Potrero Seco. 
 
 typical 
 
 Walls of tapiales thrown down, gate columns standing : 
 view of wide canyon. 
 
 B. Upper Copiapo valley, at La Sureta. A primitive plough consisting of a tree-trunk and roots. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XVIII 
 
 B. La Pampa on Rio Elqui. Columns and roof free to sway but not overthrown. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XIX 
 
 A. Copiapo.. Atacama monument, showing statue thrown 16 feet (5 meters) 
 
 from its pedestal. 
 
 B. Copiapo. 
 
 Base of Atacama monument, showing detail of brick layer sheared 
 by rotation of upper structure. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XX 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXI 
 
 A. Vallenar. Rock fall on track up Huasco valley, 
 near Quebrada Jilguero and fault line. 
 
 B. Vallenar. Railroad up Huasco valley, showing displacement of track. 
 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXII 
 
Carnegie Inst. Wash. Pub. 282 (Willis) 
 
 Plate XXIII 
 
 B. Vallenar. Quebrada Valparaiso, view of quebrada showing position of big slide with 
 reference to terrace level as seen across Huasco valley. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXIV 
 
 
 
 A. Vallenar (2 miles (3 kilometers) west of). Slide in Quebrada Valparaiso, in Pleistocene 
 
 terrace gravels, looking north. 
 
 B. Vallenar. Slide in Quebrada Valparaiso, looking north from near middle of slide. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXV 
 
 A. 
 
 Vallenar. 
 
 Quebrada Valparaiso, details of big slide showing old mass shaken down in 
 previous earthquakes and view across terraces of Huasco valley. 
 
 E. Vallenar. Quebrada Valparaiso, view of old slide, showing breaking down of mass in 
 
 last earthquake. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXVI 
 
 A. Yallenar. Slide in Quebrada Valparaiso; near view of striated surface in Pleistocene gravels. 
 
 B. Vallenar. Looking south across Rio Huasco from Quebrada Valparaiso, along fault line. 
 

Terremoto of November io, 1922 
 
 43 
 
 assumed to contain the epicenter. These conditions have not been realized in the 
 investigation of the Atacama shock under discussion. The field observations show 
 that the apparent intensity of the movements was similarly violent at widely sepa¬ 
 rated points and depended in large measure upon local conditions. 
 
 Apparent intensity is here distinguished from the actual force with which the 
 earthquake vibrations are transmitted through the outer crust of the earth. The 
 latter passes through the dense and highly elastic rocks where the pressure due to 
 superincumbent load is high. Where the vibrations emerge at the surface of the earth 
 they produce effects which vary greatly, the amplitudes and periods changing accord¬ 
 ing to the resistance offered by the relatively inelastic materials at the very surface. 
 The destructive action on buildings also varies with the nature of the superficial 
 materials that support the foundations. Inasmuch as the observed effects are thus 
 independent to a notable degree of the original force, the apparent intensity deduced 
 from them is not a satisfactory indication of the real intensity. This subject was 
 discussed at length in the report on the earthquake in northern California in 1906. 1 
 
 Four facts stand out as controlling conditions which make it impracticable to 
 draw lines of equal intensity, isoseisms, according to the surface evidence: (a) The 
 earthquake produced almost no visible effects upon the landscape of the plains and 
 mountains. There is, therefore, no evidence of intensity, not even that there was a 
 shock, except where structures had been built by man. ( b ) The region is so inhos¬ 
 pitable that habitations are very sparsely and irregularly scattered over it. The evi¬ 
 dence that may be found in their damage or destruction is consequently exceedingly 
 meager, (c) Where buildings exist or existed the nature of the foundation was 
 in most cases the controlling factor. Structures built on rock suffered little or no 
 damage. Those on gravel terraces were severely shaken, but often not with destruc¬ 
 tive violence. Those which stood on river alluvium or other soft material, especially 
 when it was filled with water, were generally wrecked. ( d ) The geologic condi¬ 
 tion of faulting also determined lines of high intensity, which fixed centers of destruc¬ 
 tive violence at the points where they crossed the alluvial fills that occupy the valleys. 
 From these considerations it follows that what we may observe on the surface in this 
 and similar cases is the apparent local intensity, a result of several strictly local, 
 unsystematic conditions. 
 
 In the course of a journey that covered the area of material damage to struc¬ 
 tures, the writer observed evidences of very high relative intensity at Vallenar and 
 vicinity, at El Transito on the Fluasco, at San Antonio on the upper Copiapo, at 
 Copiapo itself, and at Potrerillos. These places are scattered over a distance from 
 south-by-west to north-by-east of 175 miles (280 km.). The east-west diameter of 
 the area is about 47 miles (75 km.). Within an oval of these dimensions lie the sever¬ 
 est effects. But within that same area are villages, built essentially like the others, 
 which suffered little or no damage. Investigation shows that they owe their immunity 
 to the character of the material on which they are built or to the distance that sepa- 
 
 1 State Earthquake Investigation Commission, Report, vol. I, part I, pp. 160-162 and 200, 1908. 
 
 6 
 
44 
 
 Earthquake Conditions in Chile 
 
 rates them from a fault or to good construction, whereas the examination of the dam¬ 
 aged buildings led to the conclusion that the causes of failure were to be found in the 
 weakness of the foundation material or in the proximity of a fault or in the construc¬ 
 tion of the building or in a combination of all of these conditions. 
 
 A valuable group of data bearing on the local effects of the shock is contained 
 in the answers received from those who experienced it and who courteously sent in 
 answers to the questionnaires which had been distributed. The answers were studied 
 by Dr. Luis Sierra Vera, of Copiapo, an assistant to Count Montessus de Ballore 
 and a seismologist familiar with earthquakes in this region. His digest of the ques¬ 
 tionnaires will be found in Appendix II. From it we extract the following estimates 
 of intensity at various places. To complete the list some places that are not included 
 among the questionnaires, but which were visited by the writer, are included. They 
 are marked by an asterisk. The data are arranged from south to north by latitude 
 and for each latitude they are stated in the order from east to west. 
 
 Intensities deduced from questionnaires 
 
 Latitude 
 
 Longitude 
 
 Place 
 
 Intensity, R. F. 
 
 Local conditions 
 
 27° to 27 0 50'. 
 
 O / 
 
 70 50 
 
 Caldera 
 
 VII-VII 1 
 
 Rocky coast 
 
 
 71 20 
 
 Copiapo 
 
 IX-X 
 
 Marshy fill 
 
 
 70 17 
 
 Tierra Amarilla 
 
 VIII-IX 
 
 Near fault; river gravels 
 
 
 70 08 
 
 Tres Puentes 
 
 
 
 
 70 os 
 
 Loros 
 
 
 
 
 70 03 
 
 San Antonio 
 
 X 
 
 On fault and marshy fill 
 
 28° 30' to 29 0 00'. 
 
 7 1 15 
 
 Huasco 
 
 VII-VIII 
 
 Rocky coast 
 
 
 7 1 14 
 
 Huasco Bajo 
 
 IX-X 
 
 Marshy fill 
 
 
 71 07 
 
 Freirina 
 
 VIII-IX 
 
 On fault; gravel terrace 
 
 
 70 46 
 
 Vallenar 
 
 IX-X 
 
 Near faults ; marshy fill 
 
 
 70 16 
 
 El Transito 
 
 IX-X 
 
 On fault; gravel cone 
 
 
 70 12 
 
 La Pampa 
 
 VIII 
 
 Gravel terrace 
 
 30 ° . 
 
 71 20 
 
 Coquimbo 
 
 VII 
 
 On fault; rocky coast 
 
 
 71 14 
 
 La Serena 
 
 VII-VIII 
 
 Gravel terrace 
 
 
 70 42 
 
 Vicuna 
 
 VIII 
 
 Do. 
 
 
 70 32 
 
 Rivadavia 
 
 IX 
 
 On fault; gravel terrace 
 
 Examination of the preceding table shows that the maximum apparent intensi¬ 
 ties were observed in the vicinity of Vallenar (at Vallenar itself, at El Transito east 
 of the city, and at Huasco Bajo west of it). Similar effects were noted at Copiapo, 
 140 km. north-by-east from Vallenar. The surface materials beneath the two towns 
 are much the same and the apparent intensities may fairly be compared. No material 
 difference can be distinguished. We may conclude that the destructive force was 
 equally violent at these two cities and they were similarly situated with reference to 
 the fault or faults on which it originated. 
 
 We may next inquire whether the initial release of elastic strain occurred nearer 
 one or the other place; in other words, where was the focus of the earthquake? 
 
 The direction of movement of the longitudinal wave being outward from the 
 focus it affords a means of locating the latter when determinable. In the absence of 
 more exact data we have to fall back on the human testimony, which, unreliable though 
 it is, is significant when a number of observers agree. 
 
Terremoto of November io, 1922 
 
 45 
 
 From the answers to questionnaires we find that at La Serena four persons 
 recognized the approach of the earthquake from the north, while two observed east- 
 west oscillations. The latter were, presumably, the lateral vibrations that succeed the 
 longitudinal. At Vallenar two persons noted the first shock as coming from the east 
 and two from the west. Another put it down as from the south. Two others per¬ 
 ceived it to be from below upward. These last observations suggest that the city was 
 not far from the epicenter and the violence of the movements in the neighborhood 
 would confirm the inference. It happened that on the day following the great earth¬ 
 quake the direction of movement of the after-shocks was noted by telegraphy. 
 Telegraph operators at Vallenar communicating with those at Copiapo wired: “ It 
 shakes.” And those at Copiapo perceived the shock a few seconds later. 1 Thus the 
 testimony adduced indicates that the origin of the shock lay to the north of La Serena, 
 presumably at some considerable distance since the shock was weak at that place, and 
 somewhere on the further side of Vallenar from Copiapo; that is, to the south or 
 southwest of Vallenar. Observations of rock falls in the mountains southwest of the 
 city and the statements of goatherds, whose stone huts were utterly leveled (plate 
 VIII), would suggest that there was a locus of high intensity perhaps 12 miles (20 
 km.) from the town in that direction. 
 
 These deductions from the field evidence do not accord closely with the deter¬ 
 minations of origin which have been calculated from seismograms. As is stated in 
 Appendix I, Messrs. Macelwane and Byerly locate it about 85 miles (140 km.) south¬ 
 east of Vallenar. This is near El Transito, where the shocks were extremely violent. 
 They also cite the calculations of Sieberg and Gutenberg who place it 37 miles (60 
 km.) northeast of the city in an uninhabited region. It is evident that the approxi¬ 
 mate assumptions from which the results are determined do not permit of accurate 
 conclusions. The movements of the elastic rockmasses, slipping and snapping back 
 on the fault plane or planes, were exceedingly complex. The assumption that there 
 was some initial point of rupture, which could be taken as the instantaneous focus, 
 appears doubtful in the light of the above cited evidence. 
 
 STUDIES OF TAPIALES 
 
 Among the earliest efforts of the writer on arriving in the area shaken by the 
 earthquake was to discover effects from which the intensity of the shock at any 
 particular point might be deduced. The conditions in the towns were most unsatis¬ 
 factory. The wrecked buildings were of so many different types and conditions, the 
 foundation materials were so unequal in character, the evidences were so confused, 
 that no definite estimates were possible. Nevertheless, the general impression was 
 that the weak structures had failed because they were weak and not because they had 
 been subjected to very violent forces. 
 
 In the course of the field work attention was soon riveted by the mud walls, 
 which occur everywhere. They are built by tamping mud into a frame so as to pro¬ 
 duce a large block, which is called a tapiale, from the Spanish tapar, to tamp or pound 
 
 1 Oral statement of the chief telegrapher at Vallenar. 
 
46 
 
 Earthquake Conditions in Chile 
 
 down. They are of uniform size, being i meter wide, 2 meters long in the direction 
 of the wall, and 0.5 meter thick. They thus offer blocks which have approximately 
 the same resistances to oppose to any force that tends to overthrow them, a condition 
 which, on the average, gives an indication of the relative intensity in different areas. 
 By the application of West’s well-known formula one might also arrive at some indi¬ 
 cation of the acceleration of the force; that is, of the intensity. (Plates XXVII- 
 XXX.) 
 
 A little study soon showed the necessity of considering some qualifying condi¬ 
 tions. A perfect tapiale, being half as thick as it was wide, would be overthrown by 
 a force having an acceleration of 4.8 meters per second per second. But perfect 
 tapiales are rare. Moisture rising from the ground causes the corners to slough off 
 and reduces the width of the base. Similar effects are produced by hand, since it is 
 often convenient to take dirt from a tapiale in cultivating the fields or mending the 
 roads. The value of the tapiale as a seismometer is thus grievously and inconsider¬ 
 ately diminished. 
 
 Furthermore, it became evident that an impulse which had not been strong enough 
 to overthrow a tapiale in its first effect had sufficed to break off the corner on which 
 the weight was to a greater or less extent concentrated. The subsequent overthrow 
 might then be the effect of forces distinctly inferior to that which would have been 
 required if the tapiale had been strong enough to bear its own thrust upon the corner. 
 
 In addition to these considerations, it was necessary to take account of the long- 
 continued action of the earthquake, which could not have failed to produce coinci¬ 
 dences between the earthquake vibrations and the oscillations of the walls, and must 
 thus have had excessive effects. 
 
 Somewhat careful studies in the area of maximum effects, that is, from Val- 
 lenar to Copiapo, resulted in certain general conclusions that remain uncontradicted 
 by other evidence of equal validity and are probably sound, namely: 
 
 (1) Some tapiales out of any wall remained standing wherever they were 
 observed. Hence we conclude that nowhere did the acceleration attain the maximum 
 of 4.8 meters per second per second, which must have overthrown them all. 
 
 (2) Measurements of a large number of tapiales which had been overthrown 
 showed that their bases varied from 40 to no more than 25 cm. in thickness. The 
 force required to overturn them, therefore, did not surpass 4 meters per second per 
 second, and in the case of the narrower bases need not have exceeded 2.5 meters. 
 
 (3) The large proportion of tapiales which had bases near 30 cm. thick and 
 which had been overthrown indicated that an acceleration of 3 meters per second 
 square had generally been attained. 
 
 (4) These observations were made, as a rule, upon walls standing upon the 
 widespread gravel fill of the broad valleys or river terraces. The deduction is there¬ 
 fore to be applied only with due consideration of the foundation coefficient charac¬ 
 teristic of dry, partly consolidated gravel masses. 
 
 To elucidate these general statements, the specific observations are given in the 
 instances described below, and the reader is referred to the photographs of tapiales 
 which illustrate typical conditions. 
 
LlRPtffy 
 
 THE 
 
 0t ^LlNOis 
 
 university 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXVII 
 
 A. Copiapo. Detailed view of tapiale wall, which runs NW.-SE. 
 
 B. Copiapo. General view of tapiale wall running NW.-SE. and of distant wall at right angles 
 
 to it. showing effect of earthquake. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXVIII 
 
 A. Copiapo. Field in valley, southwest of city; wall of tapiales extending southwest. 
 
 B. Copiapo. Same field as in upper view; wall of tapiales extending southeast. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXIX 
 
 A. Copiapo valley, above Copiapo near Tierra Amarilla. Showing standing and fallen tapiales; 
 looking south parallel to longitudinal earthquake waves. 
 
 B. Copiapo valley, below Copiapo at Ramadillas. Showing wall of tapiales running X.-S. 
 
 parallel to longitudinal earthquake waves. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXX 
 
 A. Vallenar. Wall of tapiales near the city, extending east across the line of longitudinal 
 
 vibrations. 
 
 B. Vallenar. Narrows in the valley of the Rio Huasco caused by a fault-ridge of Paleozoic 
 rocks; looking west, down stream toward the city. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXXI 
 
 A. Copiapo. Fruit dish, showing the two hind legs, indicated by white points, on which it 
 
 danced on sideboard as shown in B. 
 
 B. Copiapo. Matta sideboard and fruit dish which made record of gyrations shown in plate 
 
 XXXII B. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXXII 
 
 A. Copiapo. Matta sideboard, the fruit dish that danced. 
 
 B. Copiapo. Matta sideboard; the record it wrote in 
 zig-zagging on the polished surface and in sliding straight 
 down and off. 
 
1 
 
 r Of ILLINum 
 
Terremoto of November to, 1922 
 
 47 
 
 A field situated about 1 km. southwest of Copiapo was surrounded by walls of 
 tapiales running south 63° west and south 27 0 east. Large sections of the former 
 were thrown, whereas in the latter only occasional blocks had been overturned. A 
 road ran parallel with the south 63° west course, along the northwest side of the wall, 
 and the tapiales had been undermined on that side by the removal of dirt, as was 
 shown by the hoe-marks on the lower corners of the blocks. They had generally fallen 
 in that direction, i. e., toward the northwest. Some had broken off at the foundations, 
 which consisted of stones placed in two rows, with the outer edge slightly raised, but 
 no wider apart than the width of the wall. Others had broken at the first joint above 
 the base. The wall running at right angles to this one remained standing, almost 
 intact. Its stability may have been due to the proximity of solid rock under the gravel 
 plain, since that side of the field was close to the hills. O11 the other hand, the direc¬ 
 tions of the two walls may have been a factor in the difference of effects. The course 
 of the standing wall, south 27 0 east, made an angle of about 35 0 with the longitudinal 
 waves of the shock. The course of the overthrown wall, south 63° west, made an 
 angle of about 55 0 with the same waves. The difference of angle may have been suffi¬ 
 cient to give the impulses an effective component in the one case and not in the other. 
 If so, it was the longitudinal, rather than the transverse, waves that overthrew the 
 
 one wall. The initial impulse advanced from south to north and should have thrown 
 
 # 
 
 the blocks toward the south. They fell toward the northwest, toward the side on which 
 they were undermined. Hence, the initial impulse did not throw them, but the elastic 
 return did. The destructive component of the force had an acceleration between 
 3 meters and 4 meters per second per second, according to measurements of the bases 
 of the blocks. The impulse in the direct course may then have approached 5 meters 
 as a maximum, but probably did not exceed 4 meters. 
 
 In the vicinity of Vallenar observations were made on many walls of tapiales, 
 and always with the same general results as to the probable intensity of the forces. 
 It is probable that the acceleration reached 4 meters per second per second, and may 
 have exceeded it, but it often was less, the foundation coefficient being a very impor¬ 
 tant factor. Walls of tapiales two blocks high had been built around the railroad 
 yards and also around some inclosures on the larger estancias. They had generally 
 stood fairly well and furnished a check on the lower walls. A good example was 
 photographed at the estancia de Buena Esperanza. (Plate XIV A.) 
 
 The following is the analysis of the reactions in this case (see figs. 4 and 5): 
 
 The dimensions were as given in the figures. Taking the two blocks as a whole, 
 the center of gravity falls at C (fig. 4), and the force required to start a turning 
 movement around one corner of the base would have an acceleration of 2.3 meters 
 per second per second. If the two blocks were one, that force would suffice to over¬ 
 throw them. They were, however, not attached, and the impulse acting upon the 
 lower would cause it to turn, while the upper remained still, in an upright position. 
 The weight of the upper would thus be thrown upon its corner and the center of grav¬ 
 ity would be transferred to C (fig. 5)- The effect is to stabilize the system and to 
 raise the acceleration to 4 meters per second per second, in the case examined, if 
 
48 
 
 Earthquake Conditions in Chile 
 
 both blocks are to be overthrown. This rarely happened, and is attributable to special 
 weaknesses where it did occur. When the upper block was thrown, it was obviously 
 due to the to-and-fro oscillations of the lower block, as a result of repeated impulses. 
 
 2 3 meters 
 per sec. 2 
 
 D 
 
 Fig. 4 —Effect of earthquake force on wall con¬ 
 sisting of two tapiales. If the two acted as a single 
 body, a force acting at C with an acceleration of 
 2.3 meters per second per second would overthrow 
 the wall. 
 
 Fig. 5 —If the two tapiales separated, then the 
 initial tilt of the lower would throw the upper on 
 to its corner P and a force of 4 meters per second 
 per second applied at C would be required to over¬ 
 throw the wall. The lower block could not be 
 overturned until the line DP' passed the vertical. 
 
 Hence it would appear that the force in this case, as in others similarly studied, prob¬ 
 ably did not attain an acceleration of 4 meters per second per second, but very prob¬ 
 ably exceeded 2.3 meters. 
 
LIBpary 
 OF fuc 
 
 UmEIISln OF l LUNOIS 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 A. Copiapo. Adobe house 70 years old, wrecked by collapse of roof: outer walls suffered but little, being held together by bean 
 
 B. Copiapo. Adobe house of one story with light roof, built around a square patio, showing shearing' 
 
Plate XXXIII 
 
LfnnMRY 
 
 Of THE 
 
 UNIVERSITY OF ILLINOIS 
 
SECTION II 
 
 GEOLOGIC FACTS, THEIR HISTORICAL DEVELOPMENT 
 AND THE DYNAMIC HISTORY OF ATACAMA 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
ROCKS OF ATACAMA 
 
 The following table of formations in Atacama is based upon a paper contributed 
 to the report of the Carnegie expedition by Dr. Johannes Felsch, who had spent seven 
 years in studying the region under the auspices of the Chilean Government. The 
 description of the geologic facts observed by him is contained in the report which he 
 prepared for this volume. See Appendix III. 
 
 Paleozoic : 
 
 Metamorphic Rocks: 
 Quartzite. 
 
 Mica schists and slates. 
 Gneiss. 
 
 Plutonic Rocks: 
 
 Granite . 
 
 Plagioclase granite . .. 
 Black diabase . 
 
 Mesozoic : 
 
 Porphyries in dikes. 
 
 Rhetic: 
 
 jBoth intrusive in the metamorphic rocks. 
 
 • Intrusive in the granite in very large dikes, accompanied 
 
 by a great deal of metamorphism. 
 
 • Possibly Paleozoic. They cut the Paleozoic gneisses and 
 
 granite and are regarded as probably Mesozoic by 
 Felsch. 
 
 Sandstones and conglomerates with 
 
 coal beds ..Locally developed. 
 
 Lower Jurassic, Lias: 
 
 Calcareous sandstone and gray 
 limestone, interbedded. 
 
 Middle Jurassic, Dogger: 
 
 Reddish gray limestones. 
 
 Labradorite porphyry .Occurs in thick beds overlying the middle Jurassic lime¬ 
 
 stones on the western slope of the Andes from San¬ 
 tiago in latitude 34 0 to 26°, as observed, and still 
 farther north and south. The zone of eruption was 
 over 600 miles long and the bedded porphyries are 
 many hundred feet thick. 
 
 LTpper Jurassic, Tithon: 
 
 Black limestones and black, cal¬ 
 careous slates. 
 
 Melaphyres or pyroxenic breccias. 
 
 Neocomian: 
 
 Greenish gray sandstones and cal¬ 
 careous shales and limestones. 
 
 Diabase in dikes and flows. 
 
 Post-Neocomian; chiefly Tertiary and 
 Quaternary: 
 
 Quartz diorite. 
 
 Diorite without quartz. 
 
 Andesite. 
 
 Pyroxene andesite. 
 
 Trachytes and liparites. 
 
 According to Felsch the andesites are more recent than the diorites and older 
 than the trachytes and liparites. Liparite flows on the upper slopes of the Western 
 Cordillera cover gravels that fill Tertiary gulleys. There is nothing more recent 
 among the volcanics, so far as present information goes. Active volcanoes do not 
 occur in the area discussed, although they rise in the Andean plateau adjoining on 
 the east. 
 
 7 
 
 51 
 
DYNAMIC HISTORY OF ATACAMA 
 POINT OF VIEW 
 
 The preceding enumeration of the rocks which occur in Atacama expresses time 
 and force. The expression of time is in the usual terms of geology: Paleozoic, Meso¬ 
 zoic, etc., apply to great eras; Rhetic, Jurassic, etc., designate periods that are dis¬ 
 tinguished within an era. The latter are names which were first applied to certain 
 groups of strata occurring in Europe or England, but which have come to signify the 
 period of time in each case during which certain species of marine shells existed. 
 Upon the discovery of those species anywhere in the world the strata in which they 
 are found are regarded as having been deposited contemporaneously with those in the 
 type locality and are assigned to the same period. The terms Rhetic, Jurassic, etc., 
 thus serve to indicate the chronologic relation of events which occurred in Atacama 
 to contemporaneous conditions in Europe or England. 
 
 The terms and the comparisons are the commonplace usage of geologic correla¬ 
 tion. In this particular case they rest upon the identification of fossils by Dr. Felsch. 
 
 The expression of force is less commonly read into such an enumeration of rocks. 
 Each rock type is, however, the result of a reaction involving the expenditure of force, 
 which is indicated in the crystalline structure or mineralogical composition of igneous 
 rocks or in the nature, extent and thickness of sedimentary rocks. The succession 
 of rocks thus expresses a sequence of dynamic reactions, which concern us in this 
 inquiry because earthquakes also are effects of a force that is presumably related to 
 the dynamics of the past. 
 
 The formation of the rocks has not been a continuous or continuously similar 
 process. It has been intermittent. Periods of rest have alternated with much shorter 
 episodes of activity. Ebb and flow of forces are expressed in superficial results. At 
 times quiet conditions favorable to the deposition of strata in shallow seas have pre¬ 
 vailed. At other times enormous masses of igneous rock have risen into the outer 
 crust and have even appeared on the surface as extensive volcanic flows. 
 
 We proceed to consider in historical sequence the dynamic effects recorded in the 
 rocks of Atacama. 
 
 PALEOZOIC ACTIVITIES 
 
 The earliest geographic condition of which there is record in this region dates 
 probably from the late Paleozoic and was that of a sea coast on the site of the actual 
 coast range of Atacama. Sand and silt were then deposited there to form extensive 
 and thick accumulations of strata. They were washed from a rising land and gath¬ 
 ered upon a subsiding sea bottom. The thickness of the strata indicates that the sub¬ 
 sidence was notable and continued for a long period of geologic time. The elevation 
 of the land was commensurate with the subsidence, since it sufficed to furnish the large 
 body of sediment. 
 
 52 
 
Dynamic History of Atacama 
 
 53 
 
 Thus the earliest effects which can be deduced from the visible rocks are those 
 resulting from the action of vertical forces which caused one zone of the earth’s crust 
 to rise and an adjacent zone to subside. The effects were gradual, the process was 
 one of long duration, and though not steady was persistent. 
 
 Changes of level of the earth’s surface, whether positive (that is, in the direction 
 of uplift) or negative (that is, in the direction of subsidence) are and have been of 
 general occurrence all over the world and during all recorded geologic ages. They 
 have been peculiarly characteristic of shore zones, indeed the existence of a shore 
 implies the establishment of a land on the one hand and a basin on the other. The 
 areas of land and sea have always been liable to greater or less modification. Thus 
 the oldest known aspect of Atacama is simply that of any shifting shore. But the 
 normal changes remain difficult of explanation in terms of the forces that cause the 
 positive and negative movements. 
 
 The action of unusual or extraordinary developments of energy is not to be 
 assumed to produce these normal, though local, changes of level. The effective forces 
 must be those which are universally available when called upon for action, but which 
 remain inactive unless special conditions incite them. When in operation they must 
 work through a mechanism that is capable of very long-continued action without 
 fatigue or exhaustion. And they must eventually almost cease to act, leaving that 
 relatively fixed condition of the earth’s surface which is recorded by peneplanation. 
 
 The group of forces which we may invoke comprises gravitation, the molecular 
 and atomic activities of mineral substances, and the exciting effects of changes of 
 temperature or heat. The mechanical effects involve the gradual transfer of rock 
 material at a considerable depth in the earth from beneath the area of a subsiding 
 trough to that of the rising land, to supply the waste that is superficially carried from 
 the land to the sea. Geologists have developed several theories to explain this move¬ 
 ment either as a flow of molten, fluid rock, or as a kind of plastic flow of solid rock 
 under excessive pressure and at high temperature, or as molecular, chemical meta¬ 
 morphism due to the effect of heating in the presence of an unbalanced elastic strain 
 at considerable depth. This is not the place to discuss the various theories. It suffices 
 to point out that the Atacama region had at the close of Paleozoic time long been the 
 scene of a gradual change of levels in two adjacent zones, presumably under the mod¬ 
 erate action of the forces of gravitation, molecular reaction, and heat. 
 
 The rocks which were produced during the late Paleozoic were the sediments 
 which now occur in metamorphosed condition as quartzites, slates, mica schists and 
 gneiss. They are now highly tilted, folded and contorted, as is usually the case when 
 strata have been crushed up in the formation of a mountain range. A very large body 
 of material has been eroded from above the masses which are now exposed in the 
 coast range of Atacama. They have therefore continued to be elevated during subse¬ 
 quent ages. The present coast range is the successor of other ranges which have 
 risen along that zone from time to time during the Mesozoic and Cenozoic eras. 
 
 The sequel to the prolonged movements of subsidence and elevation in the zone 
 of the coast range, either during the late Paleozoic or immediately following it, was 
 
54 
 
 Earthquake Conditions in Chile 
 
 the intrusion of granite. The rock occurs as larger and smaller bodies cutting across 
 and intruded into the older sediments, which are metamorphosed accordingly. It does 
 not appear as large batholiths, there being no great mass of granite like that of the 
 Sierra Nevada of California or those which constitute the coast ranges of British 
 Columbia. In this respect the occurrences in Atacama resemble those which are 
 described by Bowman 1 for that portion of the Cordillera that lies in southern Peru. 
 They are perhaps not so great in volume as the batholiths which I have observed in 
 the Patagonian Andes, though the latter also are smaller than the masses in North 
 America. Even so the volume of granite intruded into the coast range of Atacama is 
 very impressive, and sporadic outcrops of the rock further east indicate that it under¬ 
 lies some areas of the extensive Mesozoic rocks. 
 
 The intrusion of granite into the sediments which had been accumulating quietly 
 in the Paleozoic waters was the beginning of activity in the coastal region of Chile. 
 Earlier episodes of vigorous orogeny there no doubt had been, but they had been 
 succeeded by the period of quiet recorded in the fine sediments. A new chapter of 
 mountain making began. An active force had entered the crustal strip along the con¬ 
 tinental margin. We are concerned with its nature and origin. 
 
 The granite was intruded as a molten rock. It carried a large amount of heat 
 energy, which was either inherent in it from some earlier time or which had been 
 introduced into it shortly before it was forced out of its deeper site. The alternative 
 presents two diverse views regarding the state of masses within the outer shell of 
 the earth. The first, which is the older, is a corollary of the assumption that the inte¬ 
 rior of the earth is molten or contains large bodies of rock that have remained molten 
 since some primordial stage of general high temperature. The theory is discredited 
 in general by the evidences of prolonged stability of very extensive areas of the 
 earth’s crust as well as by the high degree of rigidity demanded by tidal and seis- 
 mological observations. In this particular case the supposition that a large body of 
 molten rock formed part of the lithosphere for an indefinite lapse of time preceding 
 the rise of the granite into the outer shell is negatived by the evidences of very grad¬ 
 ual changes of level while the sediments accumulated. The very moderate movements 
 of the surface which are indicated by the fine products of erosion and the steady con¬ 
 ditions of sedimentation are inconsistent with the instability of a floating crust. I con¬ 
 clude that the lithosphere had been solid to an indefinite depth beneath Atacama dur¬ 
 ing the accumulation of the strata. 
 
 The granite, although not aggregated into great batholiths, occurs in numerous 
 bodies and constitutes a notable part of the rocks as they are now exposed. It also 
 must have been solid if the lithosphere as a whole was solid. It must also, apparently, 
 have been granite. Petrologists maintain that the process of differentiation may 
 yield the siliceous rock and a more basic facies, provided that a mass of intermediate 
 composition remain liquid long enough for the appropriate chemical and gravitative 
 reactions to occur. Whatever the validity of the reasoning may be on chemical and 
 physical grounds, the geologic evidence is opposed to the assumption of immediate 
 
 1 Isaiah Bowman, The Andes of Southern Peru, Amer. Geographical Society, New York, 1916, pp. 241-243. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXXIV 
 
 A. Near Toledo, 2 miles west of Copiapo. Looking S. 62° E. on line of shearing, showing 
 
 crushing, probably on a fault. 
 
 Jr 
 
 'Jr-- 
 
 tig 
 
 
 B. Vallenar (19 miles south of). Paleozoic granite, showing jointing but not crushing, being off 
 
 any fault line. 
 
L!P d *ry 
 Of THE 
 
 university of Illinois 
 
Dynamic History of Atacama 
 
 55 
 
 differentiation prior to the intrusion of these granites. The argument which has 
 already been presented for the stability of the crust seems to preclude the presence of 
 a liquid body beneath Atacama or closely adjacent to the coastal zone for a period of 
 time sufficient to have accomplished the required segregation before the granite rose. 
 
 I conclude that the rocks were solid and, as both granitic and basic intrusions 
 occurred, solid bodies of these diverse facies must have existed in some relation of 
 juxtaposition. We are not here concerned with their antecedent evolution. The 
 episode of geologic history which we are considering was a very recent event if we 
 take account of the great age of the earth. During the eons that had preceded, the 
 processes of fusion, segregation, and intrusion had been repeated many times and 
 it is rather to be expected that they would have accomplished whatever separations 
 of mineral aggregates were possible than that a magma capable of being segregated 
 had escaped the reactions. 
 
 If the proposition be accepted that the rocks beneath Atacama were solid before 
 they were intruded into the outer shell, then the question arises as to why they melted. 
 It is a problem in dynamics and immediately concerns this discussion. Two explana¬ 
 tions are current in the modern theory: first, there may have been relief of pressure; 
 second, there may have been rise of temperature. The alternative rests upon the 
 basic deduction that pressure and heat are opposing forces which operate within the 
 globe to promote rigidity or mobility, respectively. If their tendencies happen to be 
 nicely balanced the state of the rocks will be critical. Assuming solidity, a slight 
 relief of static pressure or a slight increase of temperature will result in melting. If 
 the balance be not critical a greater change of pressure or temperature will be re¬ 
 quired to alter the state. 
 
 Let us first consider the relief of pressure as a possible cause of melting. It is a 
 facile assumption, too often made without regard to the amount of relief required 
 or the possibility of adequate relief. 
 
 We observe that cold rocks are solid at and near the surface. We have not been 
 able to penetrate the earth anywhere to a depth where they became liquid. We infer 
 from evidences already cited that as a whole they continue to be solid to an indefinite 
 depth under normal conditions. Both pressure and temperature increase, but the 
 effect of pressure in promoting solidity is normally superior to the effect of heat in 
 producing liquidity. What is the margin of superiority? No relief of pressure will 
 melt rocks at surface temperatures. A rise of temperature of more than 1,000 
 degrees centigrade is requisite to that end. From the surface toward the center there 
 are rising gradients of both pressure and heat. The normal relative rates of rise are 
 unknown, but the long-continued solid state implies that pressure maintains the superi¬ 
 ority by a safe margin. The critical state at which a slight relief of pressure would 
 produce melting is not the normal condition. We may compare this conclusion with 
 the evidence of geologic facts. 
 
 North America and northern Europe were repeatedly loaded and unloaded dur¬ 
 ing the Pleistocene by accumulation and dissolution of ice sheets. The weight was 
 sufficient to cause submergence, as evidenced by drowned shores, and the unloading 
 
56 
 
 Earthquake Conditions in Chile 
 
 was adequate to cause emergence, as shown by raised beaches. In the current state 
 of opinion some may attribute these effects to isostatic adjustments, but even on that 
 vague assumption there must have been elastic compression and elastic expansion 
 resulting in corresponding elevation and lowerings of temperature. The variations 
 have continued during a fairly long period, probably a million years or more. The 
 lateral strains induced in the outer shell have been unbalanced. These conditions 
 would have favored the extrusion of molten rock, if any had formed, but none has 
 appeared in the extensive glaciated areas. The presumption is strong that none 
 formed. We may conclude that the variations of pressure resulting from the waxing 
 and waning of the ice sheets were inadequate to disturb the normal superiority of 
 pressure over heat in maintaining solidity. 
 
 We may continue this line of reasoning by considering the case of the complete 
 development of the topographic cycle, which comprises the elevation and erosion of 
 a mountain chain and results in the removal from the surface of a load corresponding 
 to the mountain masses. There are many illustrations of the process and effect, but 
 none perhaps is more significant than that of the Appalachian province of eastern 
 North America. After having been the scene of pronounced mountain growth dur¬ 
 ing the late Paleozoic and early Mesozoic the region was reduced to one of the most 
 perfect peneplains known to us and remained in a low featureless condition during 
 the later Mesozoic and early Tertiary. It was thus for a very long time an unloaded 
 region, beneath which pressures must have been notably less than during the pre¬ 
 ceding ages. Yet there has been no eruption of igneous rocks, either as plutonic 
 intrusions or volcanic outpourings. We do not overlook the Triassic diabases. They 
 were erupted outside of the Appalachian zone, in an area of subsidence and loading. 
 
 This reasoning could be extended to other districts of the earth’s surface, but the 
 argument already advanced appears sufficient to justify the conclusion that super¬ 
 ficial changes of load do not directly modify the solidity of the subjacent sections of 
 the earth’s crust. 
 
 We turn to the consideration of another phase of this problem of relief of loads. 
 It being observed that portions of the earth’s surface are up-arched, the inference is 
 sometimes drawn that the arch must be self-supporting, at least to a notable degree, 
 and that the underlying rocks are thus relieved of pressure. 
 
 One type of broad arches or domes comprises those which are produced at the 
 earth’s surface by vertical, upward-directed pressure, which may be due to changes 
 of form of underlying rock masses or to the intrusion of an igneous mass. This con¬ 
 dition of arching, however, does not lessen the load upon subjacent bodies, since the 
 upward pressure must react from the resistance of a firm base. Arches of this type 
 are therefore excluded from the argument. 
 
 Arches or anticlines due to horizontal compression are known as competent folds. 
 They rise only in case the up-arching strata are competent to lift the superincumbent 
 load. They thus do relieve the underlying rock of the weight that they lift. They 
 develop in stratified beds having thicknesses up to 3 miles (5 km.), and possibly up to 
 5 miles (8 km.). There is, however, no fusion within the anticlines. If it be argued 
 
Dynamic History of Atacama 
 
 57 
 
 that the temperature is not high enough to cause melting in these superficial sediments 
 we may accept that explanation and proceed to consider some deeper zone beneath the 
 sedimentary mantle and therefore composed of interlocking metamorphic and igne¬ 
 ous rocks. We shall then be dealing with the outer shell or crust of the earth. 
 
 “ Folding of the earth’s crust ” is a concept not uncommonly entertained by 
 geologists, but it is one which will not withstand mechanical analysis. A solid may 
 yield to compression by bending or by shearing. It will yield in the manner which 
 meets with least resistance. Bending implies the rise of a competent anticline, if it is 
 to relieve the pressure on an underlying mass by lifting the load, and it is evident that 
 an increase of load makes bending more difficult. As we descend into the earth we 
 should encounter at some no very considerable depth a zone where the superincum¬ 
 bent load is so great that bending will be more difficult than shearing and deforma¬ 
 tion will take on the latter form. Hence it follows that competent folding is a rela¬ 
 tively superficial mode of deformation. It can not occur at a depth sufficient to 
 sustain the temperature at which rocks may melt in large masses. 
 
 It seems necessary to conclude that relief of pressure which might occasion 
 melting can not be produced by so-called folding or up-arching of the earth’s crust. 
 
 Another condition which may be postulated as lightening the load on any deeply 
 buried mass is the outflow of already molten material by channels leading out later¬ 
 ally. Of the efficacy of this process to induce melting by relieving pressure there can 
 be little doubt. The volume of rock thus removed represents in many cases a very 
 material change in the length of the column resting upon rocks from 20 to 100 miles 
 (32 to 160 km.) or more below the surface, as may be inferred by the profundity of 
 oceanic deeps. Furthermore, the temperature of the solid rock which underlies a 
 molten mass must be so high that the solid is near the critical temperature for the 
 original pressure and will pass readily into a molten state with diminution of that 
 pressure. This would seem to be a probable condition of sequential or secondary melt¬ 
 ing. It can, however, not be the cause of the first melting, which is an essential pre¬ 
 requisite. The initial cause of change of state must be sought in some other modifi¬ 
 cation of the conditions that had imposed solidity. 
 
 From whatever point of view we consider the general proposition that relief of 
 pressure has been the cause of melting, we encounter insuperable objections: either 
 the relief affects strata too near the surface and too low in temperature; or the relief 
 is not mechanically possible as postulated; or the relief occurs only as a sequential 
 effect of previous melting and the melting has still to be explained. 
 
 I conclude that relief of pressure can not be regarded as a cause of the passage 
 of rock from the solid to the liquid state in the solid earth. 
 
 Relief of pressure being eliminated as a cause of melting, a rise of temperature 
 is the only alternative cause under the postulated conditions. It is an efficient cause, 
 but there are obscurities in the manner of its development and concentration which 
 call for discussion. 
 
 A major cause of the release of energy as heat within the globe is gravitation 
 and resultant compression. A concentric distribution of temperature would result 
 
58 
 
 Earthquake Conditions in Chile 
 
 from this cause in a homogeneous globe. At any given depth the temperature would 
 be the same, or in other words the isogeotherms would be concentric spheroids. This 
 is the ideal physical concept. Among its consequences would be the conduction of 
 heat outward along radii from the heating nucleus to the surface. Chamberlin has 
 pointed out that the resultant distribution of temperature would depend upon the 
 relative rates of conduction at different depths and that there would be a rising tem¬ 
 perature within any relatively non-conducting outer shell. The postulates are: 
 (i) That the heat energy is released most vigorously in a deep, interior zone; (2) that 
 the material of the globe is densest in depth and becomes less dense from within out¬ 
 ward toward the surface; (3) that in general denser materials are better conductors 
 than are the less dense. Hence it follows that heat must be conducted to some outer 
 zone faster than it could be conducted away and must accumulate. 
 
 The effect would be to raise the temperature to the melting point, melting would 
 be followed by extrusion of the melt, and lowering of the temperature would ensue 
 in the melting zone. The process would be periodic. 
 
 In a globe composed of homogeneous layers this process would result in epochs 
 of vulcanism over the whole surface at the same time and the alternate periods of 
 inactivity would similarly affect all the continents and ocean basins simultaneously. 
 Some such alternation of conditions may be recognized in a gross analysis of geo¬ 
 logic history. The Tertiary and Pleistocene, for instance, have been periods of exten¬ 
 sive orogeny, in contrast to the inactivity of Cretaceous time in general. It is only 
 in the gross analysis, however, that the periodicity holds true. Local departures from 
 the conditions characteristic of any period have been of common occurrence and 
 pronounced degree. There is some cause of variation, which affects both time and 
 place of heat accumulation under this process. 
 
 If we turn from the deductive reasoning to the inductive and examine the facts 
 of distribution as indicated by the evidences of heat in the outer crust, we note that 
 ocean basins and mediterranea differ from continental masses in that contempo¬ 
 raneous activities characterize the opposite shores of basins, whereas diverse condi¬ 
 tions have occurred simultaneously on opposite coasts of large land masses. For 
 example: Geologic events have run parallel in Great Britain and eastern North 
 America across the north Atlantic to a remarkable degree. A similar parallelism of 
 occurrences characterizes Africa and South America across the south Atlantic., as 
 has most recently been elaborately developed by Du Toit and Reed. 1 The histories of 
 the Asiatic and American shores of even the vast Pacific basin are characterized by 
 similar dynamic events. The same is true of the Mediterranean, Caribbean and of 
 other minor basins. 
 
 On the other hand, the histories of opposite coasts of continents have been 
 dynamically different. The fact needs no elaboration. It is well known to all who 
 have compared them, as the history of Appalachia, for instance, with that of Cali¬ 
 fornia, at any period since the Pre-Cambrian. 
 
 1 Alex. L. Du Toit and F. R. Cowper Reed, A Geological Comparison of South America zvith South Africa, 
 Carnegie Inst. Wash. Publ. No. 381, 1927. 
 
Dynamic History of Atacama 
 
 59 
 
 The likenesses of dynamic histories occur between closely contiguous deeps, as 
 among the deeps within the Mediterranean, or in the Antillean area, or around the 
 margin of the Pacific. The differences are functions of remoteness from one another 
 as the Atlantic and Pacific, separated by the Americas. Common histories indicate 
 common sources of energy. Distinct histories indicate distinct sources of energy. 
 Thus the geologic records sharply contradict assumptions of a homogeneous earth 
 or of an earth composed of concentric homogeneous shells, of shells which shall be 
 chemically, physically, potentially, dynamically homogeneous, each one throughout 
 its spherical extent and radial thickness. Observation teaches that no such shell ex¬ 
 tends over the surface of the globe. The distribution of dynamic activity in time and 
 geographic position demonstrates that homogeneity does not characterize any interior 
 shell, at least to that great depth from which energy ascends. 
 
 We are concerned at the moment with heat energy only (or of energy capable 
 of transformation into heat) and with its concentration in a certain superficial seg¬ 
 ment in the transition zone between a continent and an ocean basin. We have as¬ 
 sumed conduction in diminishing degree from within outward. We have also to 
 recognize periodicity as a characteristic of the temperature changes. 
 
 A variety of hypotheses might probably be framed to meet these requirements 
 if we knew more about the organization of the interior of the globe and the physical 
 characteristics of its constituent parts under intense conditions of temperature and 
 pressure. Our knowledge is avowedly limited, but with the partial understanding 
 we possess we may frame an explanation as follows: 
 
 Heat is generated by compression or other cause deep within a deeply hetero¬ 
 geneous globe. The rate of generation is a function of variables (the physical prop¬ 
 erties of heterogeneous matter) and is itself unequal in different masses. The rates 
 of conduction away from the sources are unequal, both along radii which diverge 
 through unlike sectors and along layers that differ in conductivity. The evolution 
 of heat is very gradual, its transfer very slow. Changes of temperature toward a 
 higher degree (which alone could produce a change of state) would be correspond¬ 
 ingly long in developing. Wherever, however, in its long and tortuous journey of two 
 or three thousand miles from the deep interior toward the surface the heat energy 
 accumulated, there melting would ultimately occur and the molten body would carry 
 out its latent and sensible energy in erupting to a higher level. Thus the outward 
 progress of an accumulation of calories would be per saltum and the effects mani¬ 
 fested in the melting and intrusion of the igneous rocks of Atacama toward the close 
 of the Paleozoic would be only the final incident in a long sequence of similar move¬ 
 ments by a mass of heat energy. 
 
 There we may leave that speculation and return to the facts of the region, which 
 at once confront us with another problem. Granite was the first rock intruded from 
 below into the outer crust and it was followed after a geologically brief interval by 
 basic intrusives. It would not be necessary to discuss this particular sequence of 
 melts in order to describe the dynamic history of Atacama, but I have elsewhere 
 argued that basalt would melt before gneiss (or granite) unless gases were present, 1 
 
 1 B. Willis, Discoidal Structure of the Lithosphere, Bull. G. S. A., vol. 31, p. 296, 1920. 
 
60 
 
 Earthquake Conditions in Chile 
 
 and it is desirable to correct that statement. In the passage cited there is a numerical 
 error by which the conductivity of gneiss was given as 0.0005 instead of 0.005. By 
 correcting this error the relative rates of heating of basalt and granite are changed 
 from the calculated ratio of 4: 1 in favor of basalt to 1:2.8 in favor of granite. 
 
 There are certain additional considerations to be taken into account in review¬ 
 ing that statement. The calculated ratio is of value only in the case of a dry melt, as 
 was then recognized, but it is now becoming more evident that gases are rarely if 
 ever absent in igneous rocks and that the conditions described would be improbable 
 of occurrence. Gases are known to lower the melting points of all rocks and pro¬ 
 mote liquidity of the melt, but their relative effects on unlike magmas are not yet 
 determined in a manner to permit synthetic discussion. 
 
 It seems desirable at this point to direct attention to the probable source of the 
 granitic and later igneous rocks. It may be possible that they came from a position 
 immediately beneath the superficial zone, into which they were intruded, that is, 
 from beneath the zone of the coast range. This is, however, improbable. If it be 
 assumed, as is reasonable, that surfaces of rupture in the earth’s crust follow sur¬ 
 faces of maximum shear and that the pressure producing the shear is predominantly 
 horizontal, then the ruptures must be inclined at angles approaching 45 degrees. 
 Igneous rocks rising along these surfaces would thus come from a deep zone adja¬ 
 cent to that in which they appeared at the surface. Morever, the horizontal travel 
 distance would approximate that of the vertical rise, which may be estimated in 
 excess of fifty kilometers and up to several hundred when we take account of long- 
 continued drafts of material from the asthenosphere. When we further consider 
 that the surface of more facile rupture and intrusion is probably governed by the 
 curve of elastic stress, which flattens out to horizontality in its deeper section, 1 we 
 may well recognize that the sources of the observed igneous rocks lie at considerable 
 distance to one side of the zone of their appearance at the surface. The writer regards 
 it as more than probable that the igneous rocks of the Andean cordillera were ejected 
 from beneath the deep trough which borders South America on the west and is 
 known as the Atacama deep. 
 
 Two early phases of the dynamic activity of Atacama have been presented. The 
 one was the slow changes of level during the late Paleozoic, involving both uplift and 
 subsidence and thus requiring the exertion of a force or forces competent to over¬ 
 come gravity to the extent that the continental margin was elevated. It was a slow, 
 gradual and prolonged process. The other was the gradual heating of a great volume 
 of rock to the point at which it eventually melted. It also was a slow, gradual and 
 prolonged process. The latter went on simultaneously with at least the later period 
 of the former under the same narrow strip of the earth’s surface. Both processes 
 came to an end with the rise of the granite, or more properly speaking, both passed 
 into more vigorous phases. 
 
 Following the intrusion of the granite into the zone of the coast range of Atacama 
 there was undoubtedly an interval of comparative inactivity, during which the gran- 
 
 1 Bailey Willis, op. cit., 1920, pp. 280-284. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXXV 
 
Dynamic History of Atacama 
 
 61 
 
 ite and the metamorphosed sediments were subjected to tectonic pressures of suffi¬ 
 cient intensity to shear the granite. This conclusion follows from the fact that subse¬ 
 quent intrusions entered along shearing planes. The interval was, however, short. 
 It has been established by the observations of Cloos in Germany that granites may 
 be jointed by tectonic pressures, at least in their upper cooled portions, even while 
 the acid magma is still so fluid in some lower part as to give off aplite and pegma¬ 
 tite. 1 The same relations had been independently observed by the writer in certain 
 granites of the Coast range of California. 2 Similar occurrences of aplite are com¬ 
 mon in the granites of the coast range of Atacama and they point to the conclusion 
 that the inequilateral pressures which caused the jointing had already developed or 
 had been continuously active when the granite had solidified superficially but was 
 still molten below. 
 
 While the aplite veins are of small volume and by their chemical composition 
 belong to the granitic magma, it is quite otherwise with the great dikes of black dia¬ 
 base, which were next intruded. They are inferior in volume to the granite, but are 
 nevertheless very numerous and thick. They contrast sharply with the granite in 
 color, being black against a light ground, and resemble strata of black shale inter- 
 bedded with sandstone when viewed from a distance. They occur in all parts of the 
 zone in which the granite was intruded. The association is so constant that it seems 
 to imply a genetic relation. The sequence is moreover of common occurrence in the 
 coast ranges and islands bordering the Pacific basin. A discussion of it pertains, 
 however, rather to the province of the petrographer than to that of the structural 
 geologist. 
 
 MESOZOIC ACTIVITY 
 
 The activities described can not have occurred without producing an uplift of 
 the coastal zone in which the intrusions are now found. We may, therefore, consider 
 the Triassic period which followed as having opened with a range of mountains 
 located along that zone. The coast district appears never again to have been sub¬ 
 merged. No remnants of younger strata have been observed in it and it is properly 
 characterized as the Paleozoic coastal belt. The evidence of Triassic conditions is, 
 however, exceedingly meager. In this region it is limited to very local occurrences 
 of coarse sandstones and conglomerates, which contain small lenses of coaly sub¬ 
 stances with plant remains of Rhetic age. In the latitude of these observations there 
 is but one such deposit. It lies in the foothills of the Andes, 150 kilometers east of 
 the coast, where it may have been spread as the wash of a river flowing down the 
 eastern slope of the coast range of that period. The cobbles of the conglomerate 
 lenses, the cross-stratification of the sandstones, and even the lenticular form of the 
 coal beds suggest such an origin. The evidence is thus consistent with the inference 
 that there was a mountain range to the west along the present coast. The record 
 which was made in that zone was therefore one of erosion and has been destroyed 
 by the subsequent activities of atmospheric agencies. 
 
 1 Hans Cloos, cited in Robert Balk, Primary Structure of Granite Massives, Bull. G. S. A., p. 686, vol. 36. 
 
 2 Bailey Willis, La Force Sismique en Californie, Livre Jubilaire, Soc. Geol. de Belgique, p. 432, 1927. 
 
62 
 
 Earthquake Conditions in Chile 
 
 The Jurassic record was made in fine-grained sediments. Fine calcareous sand¬ 
 stone is the coarsest deposit; sandy shales are intermediate in grain and limestones 
 represent the finest material. All of them indicate the presence of a shallow sea 
 immediately bordered by low lands. Any monadnocks which may have survived 
 from the earlier stages of the topographic cycle must have been at some distance 
 from the shores. 
 
 The Jurassic sediments are widely distributed on the western slope of the Andes. 
 They are not found in the narrow coast range of Atacama. They appear to have 
 been deposited in such a sea as now extends between the islands of Japan and the 
 coast of Asia, the coast range corresponding to Japan and the continental mass of 
 South America representing Asia. That mass is now completely buried by post- 
 Jurassic formations, but presumably existed as a land area. 
 
 The thickness of the Jurassic formations does not appear to be considerable. 
 They are to be measured in hundreds rather than in thousands of feet. Apparently 
 thick sections were found to be repeatedly overthrust. Hence we may infer that the 
 subsidence of the zone of sedimentation was moderate, as was also the amount of 
 uplift of the areas exposed to erosion. On the whole, the orogenic activity during 
 the Jurassic period was exceedingly moderate. The forces which had caused the 
 great intrusions of the late Paleozoic had apparently become exhausted during the 
 Triassic. There are, however, two episodes in the Jurassic history which, though 
 they may be considered as relatively brief, present a catastrophic character in their 
 tremendous activity. They are represented by the eruptions of labradorite porphyry 
 in middle Jurassic times and of melaphyres toward the close of the Jurassic. 
 
 The labradorite porphyry occurs in very extensive lava flows which are some¬ 
 times hundreds of feet thick. The basic character of the rock and its large volume 
 imply the absorption of a very large amount of heat energy in the process of melt¬ 
 ing. We are here again faced with the alternative assumptions that the rock had 
 existed either as an originally melted mass or as a solid body which became molten 
 immediately prior to its eruption. The depth from which it rose is an indeterminate 
 factor in these speculations, but in either case the dynamic activity of the outer crust 
 was temporarily speeded up in the development of the eruptions. 
 
 The eruption of the labradorite porphyries was a definitely limited episode. It 
 was followed by renewed quiescence, as is indicated by the deposition of the lime¬ 
 stones of the upper Jurassic. A second episode of eruptive activity occurred during 
 the latest Jurassic time and is represented by the melaphyres. The rock appears in 
 dikes of considerable size, but of very small volume as compared with the labradorite 
 porphyry flows. It may be inferred that the forces involved were relatively of slight 
 intensity and duration. 
 
 The Cretaceous period is also represented by fine-grained sediments. The 
 eroded products of the lava flows and volcanoes of the Jurassic might be supposed 
 to be represented in the sediments either of the late Jurassic or Cretaceous, and they 
 probably are, but they were not recognized by me during this reconnaissance. The 
 Cretaceous sediments are greenish-gray sandstones in calcareous mud deposits, 
 again indicating shallow seas and low lands. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXXVI 
 
 Upper Copiapo valley. View of minor upthrust or B. Chuquicamata. View of footwall of ore deposit 
 
 ramp in Mesozoic eruptives. Beds dragged up. showing horizontal strije on footwall fault. The ore 
 
 body in front of footwall moved to right. 
 

 
 
 
 
 LIBRARY 
 OF THE 
 
 Umcm r of i Ulm 
 
 S 
 
Dynamic History of Atacama 
 
 63 
 
 Again there intervened a minor episode of intrusive and presumably extrusive 
 igneous activity, which resulted in diabase dikes and flows. They cut lower Creta¬ 
 ceous strata and are regarded by Felsch as having been erupted at the close of the 
 Neocomian period. In view of the fact that later Cretaceous sediments are lacking, 
 no definite date can be assigned to them. 
 
 Summing up the dynamic history of the Mesozoic, we recognize that on the 
 whole it was an era of moderate orogenic activity. The conditions which determine 
 the uplift of broad areas or the subsidence of geosynclinal troughs were apparently 
 lacking. They had been replaced by conditions favorable to stability. Yet eruptions 
 of molten masses occurred at three different times, and they represent the intrusion 
 of already molten magmas or the temporary activity of energetic forces, accom¬ 
 panied by a rise of temperature sufficient to produce melting, into the outer crust be¬ 
 neath this area. 
 
 TERTIARY AND LATER ACTIVITIES 
 
 The sedimentary record closes in Atacama with the lower Cretaceous strata. 
 It is possible that future more intensive surveys may discover upper Cretaceous or 
 early Tertiary sediments within the area, but none are at present known, and they 
 certainly are not extensive if present at all. Hence we conclude that not only the 
 coast range but the western slope of the Andes corresponds with a land surface which 
 has been persistent since the middle Cretaceous. Whatever sediments originated 
 from it have been deposited in the adjacent Pacific basin or in the troughs of the 
 Amazon and Parana watersheds. 
 
 The absence of sedimentary strata indicates that landscapes of early Tertiary 
 time, or possibly even of the upper Cretaceous, may still survive in some elevated 
 remnants in the coast range or Cordillera. While this may probably be so, they have 
 not been recognized. It is doubtful if they can be in the Cordillera, where the uplifts 
 have been great and erosion has resulted generally in sharp divides. It is more likely 
 that the oldest landscape remnants are to be found in the coast range, which not 
 infrequently presents broad, subdued profiles, assignable certainly to a pre-Pliocene 
 and probably pre-Miocene date. 
 
 The very powerful and intensely active forces which have raised the Cordillera 
 of the Andes thus began their effort at some time subsequent to the middle Cre¬ 
 taceous. It is difficult to distinguish stages of erosion in the effects which we recog¬ 
 nize in the actual mountains. The great heights are sculptured to a stage which 
 represents something past vigorous maturity. The divides are all sharp. There are 
 no remnants of an earlier topographic cycle. The salt basins of the high plateaus are 
 wide. Portions of them probably may be identified as valleys of erosion, others 
 are unquestionably aggraded tectonic valleys. The stage of erosion is therefore not 
 accurately recognizable. It is clear, nevertheless, that the surface is to be described 
 as mature rather than old. 
 
 The lapse of time required for the development of mature topography from a 
 previous stage of old age topography is not measurable in terms of any chronologic 
 
64 
 
 Earthquake Conditions in Chile 
 
 units. We can only proceed by comparison with mountain areas where sediment¬ 
 ary strata, lapping up on the lower slopes, indicate a recent time limit within which 
 the uplift must have begun. For instance, on the eastern coast of the United States 
 the volume and character of Miocene sediments, as contrasted with the Eocene and 
 earlier, indicate that the uplift of the existing Appalachian mountains began shortly 
 before or during the Miocene period. I am inclined to regard the oldest mountain 
 forms to be seen in the Andes as more advanced in their development than the Appa¬ 
 lachian ranges. The disparity of conditions of development may not have been so 
 great as might at first glance seem probable, for the older Andean ranges were 
 sculptured at an altitude far below that which they now have. If the comparison is 
 valid the more advanced topographic forms have been longer exposed to the erosive 
 agencies and consequently their topographic cycle would have been initiated in some 
 pre-Miocene time. 
 
 This line of reasoning leads me to think that the uplift of the Cordillera began 
 possibly during the late Cretaceous, but more probably during the early Tertiary. 
 It was a dynamic beginning of the first importance. 
 
 The dynamic activity which we thus assign to the greater part of Tertiary time 
 and to the relatively brief section of the Quaternary including the Present has been 
 a consistent if not a continuous activity. The slopes of the Andes are scored with 
 young canyons, which represent later Tertiary and Pleistocene erosion. In the river 
 valleys there are voluminous coarse fluviatile deposits, which probably go back to 
 the Pliocene and which have been tilted, greatly elevated in some areas, and pro¬ 
 foundly eroded. They record intense erosional activity, which exhibits phases of 
 aggradation and corrasion, probably because of changes of climate rather than be¬ 
 cause of pauses and renewals of movement during the uplift. 
 
 Thus the physiographic evidence, which is described and discussed more in detail 
 in another chapter, indicates that orogenic forces have been active in Atacama since 
 the early Tertiary. The effects of their activity are among the most stupendous, even 
 among those of the great young mountain ranges of the world. 
 
 Volcanic eruptions have constituted an important phase of the orogenic activity 
 throughout all its later stages and probably from its beginning. Both acid and basic 
 igneous rocks have been extruded in great volume in the western slope of the Cordil¬ 
 lera and along its crest. According to Felsch diorites constituted the earliest facies, 
 and they have been followed by andesite, pyroxene andesite, acid trachytes and lipa- 
 rites, in the order named. This may be the dominant sequence, but the inference 
 rests upon reconnaissance work over but a small part of the mountain chain, and 
 can not be accepted as a fact upon which to base petrologic theories. The outstanding 
 fact is that the igneous rocks comprise a wide range of facies and consequently indi¬ 
 cate variety of effects or of origins in the deep-seated zone of fusion. 
 
 An eruption of igneous rock represents an invasion of the region by heat from 
 a subterranean source. The heat energy may have been contained in rock masses 
 buried at very great depth, which struggled up to the outer crust, bringing their heat 
 with them. Or it may have been conducted in successive waves from sources where 
 
Dynamic History of Atacama 
 
 65 
 
 other forms of energy were transformed into heat. Or again it may have been devel¬ 
 oped by chemical or physical changes in the asthenosphere at a moderate depth below 
 the surface. However widely speculation may range among these and other possible 
 hypotheses, the outstanding fact which must be considered is that heat energy has* 
 been supplied to a zone subjacent or adjacent to the Cordillera at a depth from which 
 the igneous rocks have come. The process has been continued during many millions 
 of years. Impressive though these terms appear in our measures of time, a million 
 years is but a brief interval in geologic ages. Yet the aggregate, which covers Ter¬ 
 tiary and post-Tertiary eras, is indeed long continued. The inflow of heat has been 
 a geologic process, not merely in the conditions of its origin and in the character of 
 its effects, but also in the duration of its action. We must recall also that similar 
 effects were produced during three episodes in the Mesozoic and during one greater 
 activity at the close of the Paleozoic. The earlier history is unknown. 
 
 The extrusion of igneous material is a local phenomenon. It is characteristic 
 in Atacama of a belt which is but a hundred miles in width and which borders the 
 Pacific basin. The eruptive activity thus represents that well-established relation of 
 location in the margin of an ocean basin which has been recognized throughout the 
 world. We may fairly draw the conclusion that in this marginal zone, where the 
 ocean basin meets the continental plateau, there exists a condition favorable to the 
 accumulation of heat energy which results in the melting and extrusion of rock; 
 that this condition is a permanent one which has survived the various changes result¬ 
 ing from the activity; but that the heat supply is more or less intermittent and decid¬ 
 edly variable in concentration and amount. 
 
 In what has preceded we have spoken of the uplift of the Cordillera and of the 
 extrusion of igneous rocks from some deep-seated source as though we were dealing 
 with a simple vertical movement in either case. The great overthrusts which are 
 found to characterize the Cordillera oblige us to recognize horizontal displacement 
 as well as vertical elevation. The horizontal component of movement on the upthrust 
 faults appears to be large as compared with the vertical component, judging by the 
 manner in which masses of older rocks are superimposed upon younger. The obser¬ 
 vations are not conclusive on this point since we have no exact measurements, but 
 even if the vertical should prove to be the larger effect on the upthrust faults the 
 horizontal is a notable displacement. The thrusts are steeply inclined at the surface 
 in many places, but dip toward the west. Where the deeper canyons are cut across 
 them they are seen to assume gentler dips in their lower exposures and to extend 
 downward and westward toward the Pacific. The evidence indicates that they are 
 minor thrusts of a great overthrust structure of the Scottish Highland type. 
 
 There are many of these minor thrusts, which, even though they be called minor 
 in relation to the whole stupendous structure, would each one be considered a thrust 
 of notable extent in any mountain range of less magnitude. Fourteen of them were 
 observed in the comparatively narrow zone covered by our reconnaissance. In their 
 spacing and parallelism they resemble the overthrusts that have been mapped in the 
 Paleozoic belt of eastern Tennessee, and are probably of similar dimensions. 
 
66 
 
 Earthquake Conditions in Chile 
 
 The structures in Tennessee are relatively very ancient, and any evidence that 
 may once have existed as to the sequence of their development has been eroded. That 
 is not the case in Atacama. The topographic surface developed in the process of 
 thrusting is still recognizable and presents differences of aspect as we go from west 
 to east. It is older in the west and very young, indeed actively developing, in the east. 
 
 To state the evidence of this important fact: the coast range of Atacama pre¬ 
 sents deeply eroded fault scarps, which are recognizable only with difficulty and 
 would not surely be identified as effects of faulting without the stratigraphic evidence 
 of displacement. Moreover, these faults have not been active since the period of 
 aggradation when the rivers deposited the gravels that filled their older valleys and 
 now constitute the terraces bordering their recent channels. These terraces extend 
 with unbroken evenness across faults that bring Paleozoic to rest upon upper Meso¬ 
 zoic strata. Since the gravels are in part at least as old as early Pleistocene, the 
 faulting in this region may fairly be considered to have become inactive by the close 
 of the Pliocene. Subsequent deformation has taken the form of a more general uplift 
 of the coast range belt. 
 
 In the higher Andes the topographic expression of the fault scarps is more 
 obvious. The scarps are younger than they are farther west. The gravel terraces 
 extend evenly up to 11,000 feet along the Rio Salada and presumably elsewhere, but 
 they are seen to be greatly displaced by faults in the elevated section of the water¬ 
 shed of the Rio Elqui, and this condition probably exists farther north and south. 
 Thus the thrusts which outcrop in the high plateau region are younger, or have con¬ 
 tinued to be active longer, than those of the western foothills and the coast range. 
 
 According to personal communications from Felsch and Keidel, active over¬ 
 thrusts appear at the eastern side of the Andes down to the base where the alluvial 
 slopes of the Chaco begin. The descriptions indicate structures even younger than 
 those which may be recognized in the high plateaus. 
 
 Thus, as we go from west to east we recognize evidences of a progressive devel¬ 
 opment of horizontal displacement. It is similar to the progressive thrusting pro¬ 
 duced by Cadell in his experimental investigations of Highland structures. 1 The 
 development has been from the Pacific basin into the continental plateau. The effect 
 has been to shear off the margin of the continent and push it eastward. 
 
 GENERAL GEOGRAPHIC RELATIONS 
 
 We have recognized that the Cordillera of the Andes is composed in large part 
 of igneous rocks extruded from some deep-seated source. Their volume is great. 
 As piled up on the earth’s surface it is a great mountain chain. The space from 
 which it came must now be represented by a depression of similar dimensions. Such 
 a depression constitutes the adjacent section of the Pacific basin and is known as the 
 Atacama deep. We have seen that the movement of the overthrust masses of solid 
 
 1 H. M. Cadell, Experimental Researches in Mountain Building, Trans. Roy. Soc. Edinburgh, vol. XXXV, 
 p. 342, fig. 2, 1887. 
 

Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 ' ' A W? £'*■+<■* 
 
 
 
 -..jo*** -j-_ 
 
 — •*- 1* ^ - 
 
 --•l- r^ ar* 
 
 ” v; '- c- » 
 
 * >T«* V. • • 
 
 
 A. Quebrada de Paipote, near Puquios. T 1 
 
 B. Quebrada de Paipote, La Puerta. Massive flows of ) 
 
Plate XXXVII 
 
 a. faults in Jurassic limestone and intrusives. 
 
 Idorite porphyry of Jurassic age upturned to steep angle. 
 
LIBRARY 
 OF THE 
 
 UNIVERSITY OF ILLINOIS 
 
Dynamic History of Atacama 
 
 67 
 
 rock was from the Pacific toward the continent. The relative positions of the deep 
 and the mountain chain indicate the migration of molten igneous rock in the same 
 direction. 
 
 The consistent testimony of all the structural relations and successive develop¬ 
 ments which have been traced in this review of the dynamic history of Atacama 
 shows that the source of energy lay to the west of the continental margin beneath 
 the adjacent zone of the oceanic basin; that heat and pressure differences have there 
 been effective agents to bring about changes of a very active character during certain 
 intervals and of a less active, more gradual character during intervening periods; 
 and that the effect has been to bring toward the surface rocks, which either cooled 
 and crystallized at some subterranean depth or took on a crystalline state after hav¬ 
 ing been extruded. Crystallization is thus seen to have been the characteristic 
 tendency of the rocks in transition states, and may be supposed to have occurred 
 not only in course of solidification from a molten condition but also during the 
 progress of metamorphic changes resulting from unbalanced pressures and rising 
 temperatures in solid rocks. The solid masses lying in their deep habitat must have 
 gone through wide ranges of temperature in passing from the solid to the molten 
 condition. Only that portion could become molten which possessed the most favor¬ 
 able conditions for melting, namely, high conductivity, low specific heat and lowest 
 melting temperature in the presence of gases. The balance of the complex must have 
 remained solid and have been altered by recrystallization in adjustment to stress 
 environment. 
 
 The dynamics of the great eruptive activity which has characterized Atacama 
 at intervals since the Paleozoic as well as of the great displacements in consequence 
 of which the Andean cordillera has been upthrust are therefore to be explained as 
 originating in conditions that existed and continue to exist beneath the Atacama deep. 
 Heat has been the disturbing energy and it has brought into play the otherwise inert 
 molecular forces. Gravity and its tangential resultants have been the directive forces. 
 
 The Atacama deep and the Andean heights have had a concurrent and coor¬ 
 dinated development. 
 
 8 
 
INVESTIGATION OF THE EARTHQUAKE MECHANISM 
 
 METHOD OF ATTACK 
 
 It is assumed in earthquake research that the shock originates from a peculiar 
 mechanical structure, which will be found in the rocks of the affected region. The 
 geologist expects to distinguish certain mountains, or masses equivalent in magni¬ 
 tude to mountains, which may be regarded as mechanical or structural units in the 
 sense that each one would vibrate or move as a whole, if it were caused to vibrate or 
 move at all. 
 
 Furthermore, it is established that tectonic earthquakes, that is to say, earth¬ 
 quakes that are related to the structure of the region and not to volcanoes, are very 
 definitely connected with crushed zones or faults, as they are called. A crushed zone 
 is produced where two mountain masses rub past one another in slipping or turning 
 under great pressures that develop in the earth’s crust; and when we find such a 
 fault we have discovered that place where earthquakes have occurred and perhaps 
 are occurring. In the latter case the fault is still active. 
 
 Thus the geologist who would locate an earthquake looks for crushed zones or 
 faults, which bound or sometimes cut through mountain masses. 
 
 In the ordinary practice of geologic investigation, as it has been carried on for 
 a hundred years or more, a fault is recognized by evidences of movement, by distur¬ 
 bance of the orderly relations of rocks. To understand this, it is necessary to recog¬ 
 nize that in any region some rocks are older, some are younger, and they occur in 
 orderly relations unless disturbed. If we know what the order of the rock deposition 
 is we can trace it as far as it has not been disturbed, and so may determine the extent 
 of a structural unit. Or, per contra, we can trace a fault by that lack of orderly rela¬ 
 tions among the rocks, which is peculiar to a zone of crushing or displacement. 
 
 In the last 40 years there has been developed another method of identifying 
 active faults, which consists in tracing the extent of a structural unit by the conti¬ 
 nuity of its landscape surface and detecting the fault zones that bound it by the 
 interruption of that continuity. This may best be made clear by an example. 
 
 The Sierra Nevada of California is a structural unit which is some 600 miles 
 (850 km.) long and 75 or more miles (120 km.) wide. We recognize it as a unit be¬ 
 cause its western slope is practically an unbroken plane, if we conceive the recently 
 eroded canyons to be filled up. The plane surface can actually be seen by connecting 
 the gentler slopes across the deeply cut ravines or canyons, and can be traced through¬ 
 out the length of the mountain block as well as from the Great Valley to the crest of 
 the range. That this plane surface was originally a plain that stretched nearly level 
 over the site of the present mountains, and that it has been tilted westward with the 
 upheaval of the Sierra, is an inference that is justified by the reasoning of physiogra¬ 
 phy, the science of earth-sculpture. 
 
 68 
 
Investigation of the Earthquake Mechanism. 
 
 69 
 
 At the summit of the Sierra Nevada, however, the long slope that rises from the 
 west is cut off by the abrupt eastern face. Standing on the crest and looking east one 
 looks down on Nevada, whose desert basins lie at one’s feet, but 3,000 to 10,000 feet 
 (1,000 to 3,000 meters) below. One is looking down the eastern face of the struc¬ 
 tural unit, of the Sierra Nevada block. At its base is a crushed zone where the block 
 conies in contact with other masses, and along that zone or fault earthquakes occur 
 from time to time. 
 
 Thus the existence of the great fault may be recognized at a glance, even though 
 the details of the crushed and shifted rocks are hidden in the foothills. It is an exhila¬ 
 rating experience, as many a climber knows, to ascend to a mountain crest and let 
 the eye sweep over the distant view. It is no less inspiring intellectually to have a 
 vision of the structure of a mountain range and to read its history as recorded in its 
 landscape features. 
 
 Active faults were first recognized by G. K. Gilbert and I. C. Russell, early geo¬ 
 logical explorers of the desert basins and ranges of Nevada and eastern Oregon. 
 There the mountain blocks are forced up like arctic ice flows in the pressure ridges 
 described by Peary, and their fractured faces stand as great escarpments, several 
 thousand feet high and tens of miles long, overlooking the desert plains. Beneath 
 the latter lie buried the depressed edges of tilted blocks or of blocks that have not 
 shared equally with the general uplift of the whole crushed, faulted mass of Cali¬ 
 fornia, Nevada and Oregon. 
 
 The observations of Gilbert and Russell in regard to what is known among 
 geologists as “ Basin Range structure ” were long questioned by their colleagues, 
 who were familiar only with the mountains of the eastern United States or of north¬ 
 ern Europe, where the existing faults have so long been inactive that their surface 
 features have been eroded and they can no longer be distinguished in the landscape. 
 Incidentally, we may note in passing that these are regions where earthquakes are 
 few and far between. But it is now established and widely recognized that these two 
 pioneers in the geology of the West saw with a clear vision and correctly interpreted 
 the facts of Basin Range structure as displayed in the relations of the rocks and also 
 in the escarpments and slopes of the mountain blocks. 
 
 The year 1906 1 recorded an impressive confirmation of the view that active 
 faults are marked by recognizable details and by larger elements of the topography 
 of a region in which they occur. The earthquake which shook the coast ranges of 
 central north California and caused the great conflagration which destroyed San 
 Francisco left its trace in the surface of the ground in such unmistakable fractures 
 that it could be followed accurately for some 200 miles (320 km.), sometimes as a 
 single line of displacement, sometimes as a wide zone of complicated breaks in the soil 
 or rocks. Subsequent studies have developed the method of physiographic or land¬ 
 scape investigation with a view to tracing active earthquake faults, and it now holds a 
 recognized position as a means of identifying them. Since it requires only the intelli- 
 
 1 A. C. Lawson, The San Andreas Rift as a Geomorphic Feature; the California Earthquake of April iS, 
 1906, State Earthquake Commission, Report of. Carnegie Inst. Wash., Pub. No. 87, vol. I, Part I, p. 25, 1908. 
 
70 
 
 Earthquake Conditions in Chile 
 
 gent comparison of the surfaces and slopes of hills and valleys, as one passes them in 
 traveling, it can be carried out over an extended area far more rapidly than would 
 be possible in making a geologic survey of the rocks. But because the causes of land¬ 
 scape features are often capable of more than one interpretation, the physiographic 
 method is suggestive rather than conclusive, and its indications should be checked by 
 studies of the rocks wherever possible. 
 
 The writer, having received many early suggestions from Gilbert, had used the 
 physiographic method to identify active faults in regions as widely separated as 
 China, the western United States, and the Alps; and more recently, in the investi¬ 
 gation of the earthquake districts of California, he had gained considerable familiar¬ 
 ity with the peculiar characteristics of the live mountain ranges, that is ranges which 
 are actively growing at the present time. It was therefore a natural consequence of 
 his experience that he should approach the study of the earthquake regions of Chile 
 through the physiographic method, especially as the rock geology of those regions 
 is but little known and local geologic maps are entirely lacking. It must be recorded, 
 however, that he met with a decided setback and found it necessary to revise his 
 assumptions in this unfamiliar region. 
 
 HYPOTHESIS OF EARTHQUAKE ACTION 
 
 In the course of the first weeks of work in Chile, in February and March 1923, 
 the writer’s ideas regarding the origin of earthquakes in that country underwent a 
 change, because he failed to find the kind of evidence necessary to sustain the hypo¬ 
 theses with which he had come prepared by previous experience. In order to make 
 clear the evolution of his conclusions, it is necessary to state as a background the 
 conditions which are known to govern earthquakes in California. 
 
 It is most natural to compare California and Chile from many points of view. 
 They are similarly situated with reference to the deep ocean basin of the Pacific and 
 to the high cordillera that marks the margin of the continents. Each country is com¬ 
 monly described as presenting a coast range and a longitudinal valley west of the 
 major mountain-chain; and there is enough basis of fact for this item of the com¬ 
 parison to give it color, although the longitudinal valley in California is much larger 
 and more continuous than the basins which form the corresponding but interrupted 
 zone of depressions in Chile. 
 
 These geographic similarities extend to the geologic history. In both regions 
 the earliest recognizable disturbance of the stability of the crust was by the intrusion 
 of masses of granite. In both there was a sequence of more basic intrusions and 
 also of great changes of level. The movements continue in both countries in a some¬ 
 what similar manner and earthquakes result from the displacements of mountain 
 blocks. In view of these likenesses it seemed probable that the mechanical structures 
 of the mountain ranges of Chile would be found to be similar to those which had 
 been observed in California and that earthquakes would be traced to instantaneous 
 displacements on faults, such as occur in the latter State. This expectation was not 
 realized. 
 
Investigation of the Earthquake Mechanism 
 
 71 
 
 In California the earthquake faults are vertical planes. From the line by which 
 they may be traced on the surface they extend vertically down into the earth’s crust, 
 as may be seen in the small exposures where the dislocated rocks come in contact in 
 cliffs. How far down into the earth the fault planes maintain this vertical attitude 
 we do not know. It is the common practice of geologists to draw them as though they 
 extended indefinitely toward the center of the earth, but there is reason to believe 
 that they curve and are features of a superficial shell which may be not more than 
 50 to 100 miles deep. 
 
 In moving on these vertical fault planes the mountains of California slip upward 
 and also horizontally past each other. In any individual earthquake movement either 
 the vertical or the horizontal displacement may be the greater, but the sum of hori¬ 
 zontal displacements added up during the ages is represented by miles, while the 
 vertical offsets may be measured in hundreds of feet. Thus the horizontal movements 
 are materially larger than those in a vertical sense. 
 
 The movements described in the last paragraph are in active progress in Cali¬ 
 fornia today, and the features of the landscape to which they give rise, being per¬ 
 sistently renewed, are not obliterated by erosion, although they are frequently modi¬ 
 fied by it. They can therefore be seen. Where the vertical element of movement has 
 been notable the upraised mountain block presents a steep, straight face. Where the 
 displacement has been chiefly horizontal there is usually a long straight valley. If 
 the fault is a simple fracture the mountain slopes on either hand may rise from it with 
 curves that are distinctly convex upward, looking like a pair of compressed lips. 
 Or it may happen that the fracture zone is very wide and includes within its crushed 
 belt masses of rock which have been squeezed out as one would squeeze an apple seed 
 between fingers. Such masses may have the dimensions of large hills or even of 
 smaller dependent ranges, where the fault branches and encircles them. There are 
 many subsidiary topographic features of the active fault zones of California which 
 might be looked for in Chile, provided the faults there were equally active. That they 
 are so probably no geologist would doubt, in view of the very pronounced earthquake 
 activity of the country—but there are material differences. 
 
 In my three days’ journey from Valparaiso to Copiapo, I recognized in the land¬ 
 scape some similarities with California and I expected to find in the valley of Copiapo 
 the evidences of a great earthquake fault similar to the well-known San Andreas 
 fault. But I looked in vain for the corresponding long, straight features of the land¬ 
 scape, either of mountain scarp or valley. Copiapo lies in an oval basin, surrounded 
 by mountain ridges which are everywhere sculptured to a greater or less degree, 
 according to the softness or the hardness of the rock, but which nowhere exhibit the 
 characteristic profiles or contours produced by recent faults. After spending a couple 
 of weeks in vain search for the features which I expected to find, I returned south¬ 
 ward to Vallenar and Coquimbo, but was there equally baffled. 
 
 It is true that to anyone who is looking for evidence of faulting in the mountain 
 ranges of northern Chile certain long straight ridges appear suggestive. They 
 trend rather uniformly from south by west to north by east and they seem to repre- 
 
72 
 
 Earthquake Conditions in Chile 
 
 sent elongated fault blocks, especially where they border the depressions of the longi¬ 
 tudinal valley. In some views, such as the one which may be seen looking southwest 
 from above Vallenar across the valley of the Huasco, there is in the distant sky-line 
 of the coast range the profile of an elevated plateau that slopes toward the ocean. It 
 awakens the thought that the wide mountain block of which it is the summit has been 
 tilted westward like the Sierra Nevada and should be bounded on the eastern side 
 by a steep face, a fault scarp. There are many other similar suggestive features, but 
 when they are closely examined it is found that erosion has progressed so far in its 
 work of destroying the original mountain-face that its character as a fresh fault 
 scarp has been carved away. 
 
 Thus throughout the landscape of Chile I found suggestion but no proof of the 
 existence of those vertical faults which I had learned to recognize in California by 
 their landscape features. It looked as though the region had once been the scene of 
 energetic active faulting, but that it had passed through the stage of activity in which 
 California now is and had become quiescent; and yet there was the fact of frequent 
 and severe earthquake movements affecting this apparently dead structure. 
 
 I was greatly puzzled and anxious lest the investigation should prove incon¬ 
 clusive on this vital question of the origin or structural location of the earthquakes. 
 Eventually, however, it occurred to me that I might have to deal with a type of struc¬ 
 ture which is well known to geologists and which consists of a gently inclined fault. 
 It can best be described perhaps by comparing the fault with the bottom of a platter. 
 The edge of the platter represents the outcrop of the fault at the surface of the ground, 
 and the under surface of the platter corresponds with the fault surface, which, after 
 descending somewhat steeply into the earth, soon curves toward the horizontal and 
 assumes a gentle inclination. 
 
 We must not be deceived by the simile of the platter into thinking of something 
 of small dimensions. We are talking of mountains, of mountain ranges, and even 
 of mountain chains like the Andes. Such a fault, then, might well extend for hun¬ 
 dreds of miles along the earth’s surface, might have its upper edge in the heights of 
 the Cordillera, and prolonged downward might extend far out under the Pacific. 
 Such was the concept which came to me one March morning in Coquimbo. 
 
 Assuming such a flat fault plane, the more nearly vertical faults that I seemed 
 to have seen and that I believed existed could be accounted for as minor features 
 of an enormous structure, which branched from the great underlying plane and 
 curved upward to the surface. Such a compound structure, consisting of a great 
 major fault, or thrust as it is called, and of minor thrusts, was first recognized by 
 the English geologists Peach and Horne as existing in the northwest highlands of 
 Scotland. It has therefore come to be known as Highland structure. But the Scot¬ 
 tish example is fossil. It was once active, but geologic ages have passed since it 
 vibrated to an earthquake. Knowing this, it was a peculiar thought to realize that I 
 might be studying a similar but vigorously active structure. 
 
 If the earthquake region of Chile were really underlain by a great major thrust, 
 the displacements which caused the earthquake shock took place some miles beneath 
 
Investigation of the Earthquake Mechanism 
 
 73 
 
 our feet and could not be seen. The elastic vibrations would, however, be transmitted 
 with peculiar intensity up the minor thrust planes to the surface, and would there¬ 
 fore be most severely felt along the lines of outcrop of these faults. They might or 
 might not be accompanied by visible local displacements. My observations indicated 
 that in general they were not. 
 
 There were obviously two things to be done. One was to search for the outcrop 
 of the major thrust plane, which might be supposed to emerge along the crest of the 
 Andes, that is, along the edge of the platter. The other was to prove the existence of 
 the minor thrusts by discovering evidence of faulting in the rocks in relation to the 
 suggestive features of the landscape. It may perhaps be asked why I had not already 
 attempted to apply geologic criteria to the solution of the fault problem. I had indeed 
 made the attempt, but unsuccessfully, because I did not know the relative ages of 
 the various kinds of igneous rocks of which the ranges of this part of Chile chiefly 
 consist, and minute crushing is so general a phenomenon among them that the dy¬ 
 namic evidences of faulting are greatly obscured. It was only with the assistance of 
 Dr. Johannes Felsch, a Government geologist who afterward accompanied me, that 
 I was able successfully to attack this part of the problem. 
 
 Realizing that the more promising field of observation was to be sought high up 
 in the Cordillera, I accepted an invitation to visit the Potrerillos copper mine. It lies 
 at an altitude of 12,000 feet above the sea, about 80 miles northeast of Copiapo, in 
 the general direction taken by the earthquake wave in its passage from Coquimbo to 
 Vallenar and Copiapo. The buildings in Potrerillos had also been severely shaken. 
 The place therefore lay in the earthquake track which, beyond it, passed into the salt 
 basins of the high plateaus of the Andes, where it left no trace. 
 
 At Potrerillos, thanks to the cordial assistance given by the officials of the min¬ 
 ing company, and particularly by James E. Harding, geologist, my search was suc¬ 
 cessful. Among the rocks of the neighborhood there is a thick series of marine lime¬ 
 stones and shales of late Jurassic or early Cretaceous age, and many faults traverse 
 this stratified mass. They are thrust faults; that is to say, they are dislocations pro¬ 
 duced by compression, and they divide the strata into sections which have been pushed 
 over each other until they lie like scales on a fish. One could see the same strata re¬ 
 peated in each separate section and the sections lying above one another, although 
 when originally deposited each stratum had been a continuous bed. 
 
 From the geological point of view the opportunities for observation in the Andes 
 are superb. Cold and aridity combine to reduce vegetation to a minimum; the wind 
 blows away the soil; there is bare rock everywhere. In general, one can ride a mule 
 where one pleases, the long slopes being covered with broken rock. This is to a cer¬ 
 tain extent a drawback to observation, but the jutting ledges and cliffs are sufficiently 
 numerous, especially in the deeply cut canyons, to indicate geologic relations. 
 
 I spent ten days at Potrerillos and fully verified the initial observations. It was 
 demonstrated to the satisfaction of Mr. Harding and later on of Dr. Felsch that we 
 had to do with a structure of the Highland type. It appeared, however, that the 
 faults which traverse the range at Potrerillos were still minor thrusts. We could 
 
74 
 
 Earthquake Conditions in Chile 
 
 not reach the outcrop of the great major thrust at the bottom of the structure, which 
 probably skirts the eastern base of the Cordillera in the foothills along the edge of 
 the pampas. Its existence there has been recognized by Dr. Johann Keidel, of the 
 Argentine Geological Survey, and also by Dr. Felsch, both of whom subsequently 
 described it to me. 
 
 From Potrerillos I went some 200 miles (320 km.) north to Chuquicamata, the 
 other great copper-mine of the Andes Copper Mining Company, where also I was 
 received as a guest and given every opportunity for geologic study. Flat-lying 
 thrust planes were found to traverse this region also, and it became apparent that 
 here, as at Potrerillos, the conditions governing the formation of the ore deposits 
 were intimately related to them. 
 
 Returning from Chuquicamata to Potrerillos, I was there joined by Dr. Felsch, 
 and in his company, assisted by his intimate knowledge of the rocks of the country 
 which had been gained during seven years of geologic exploration in this region, I 
 spent six weeks in tracing out the system of minor thrusts along which the vibrations 
 of the earthquake had been transmitted with greatest intensity. 
 
 Thus the investigation resulted in the development of an hypothesis materially 
 different from that with which I had approached the problem. Without reviewing 
 the steps of its development, we may state the well-established conclusion: The earth¬ 
 quakes of Chile are of the tectonic type, that is to say, they originate in and are trans¬ 
 mitted according to the geologic structure of the country. They are independent of 
 volcanoes, although they may affect the latter. The particular structure with which 
 they are related is of the Scottish Highland type, consisting of one or more gently 
 inclined major thrusts and a large number of minor thrusts. The major thrust or 
 thrusts are surfaces of rupture which originate beneath the Pacific Ocean basin and 
 rise gently to their outcrop in the eastern base of the Andes. They are of great extent, 
 underlying some unknown part of the ocean basin, the zone of the coast ranges and 
 longitudinal valleys, and the mountain chain of the Cordillera. There is reason to 
 think that their area is to be measured not merely by tens of thousands of square 
 miles, but may extend to several hundred thousand. Such would be the indication 
 of the transmission of earthquake shocks of marked intensity over so vast an area as 
 that in which the terremoto of November 10, 1922, was felt. It alarmed people from 
 Iquique in the north to Concepcion in the south, a distance of 1,600 miles (2,500 km.). 
 It did damage to buildings at an elevation of 10,000 feet (3,000 meters) in the Andes, 
 and it shook the volcanic island of San Felix, 850 km. off the coast, in the Pacific. 
 Within the area of this effect, however, there appear to be several earthquake dis¬ 
 tricts. The historic record suggests separate structures since they do not snap simul¬ 
 taneously. Their distribution indicates that there is an equal number of major 
 thrusts, each one of which is independently active. Valparaiso, for instance, suffered 
 from a severe earthquake in 1906; Copiapo in 1918 and again in 1922. On each date 
 the shock was smartly felt at the other place, but not with that effect which would 
 have been experienced had the particular shock originated on the local fault. 
 
Plate XXXVIII 
 
 Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 A. Quebrada de Paipote, near La Puerta. Conformable sequence of Jurassic sediments and 
 
 lava flows. 
 
 
 
 , -Cs-sC A* 
 
 
 
 B. Quebrada de Paipote, near La Puerta. Faulted Jurassic sediments with ravine developed 
 
 on fault zone. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XXXIX 
 
 Potrerillos, Quebrada Asientos. Overthrust in Neocomian limestone and shale series. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XL 
 
 A. Potrerillos, Quebrada Asientos. Normal sequence of Neocomian limestone and shale; cross- 
 
 bedded limestone. 
 
 B. Potrerillos, Quebrada Asientos. Neocomian limestone deposited on granite with basal layer 
 
 of arkose sandstone. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLI 
 
 A and B. Potrerillos, Quebrada Asientos. Views of Neocomian limestone in the zone of thrust faults. 
 

 
 
 
 
 
 
 ' 
 
 
 o 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 -o) 
 
 A. Hoen & Co. Lith. 
 
 *?rV "odulaK 
 
Plate XLII 
 
 EARLY CRETACEOUS OR UPPER JURASSIC STRATA 
 
 a 
 
 c 
 
 Columnar 
 
 Section 
 
 L —-- eooft 
 
 ^>< r 
 
 * 
 
 -X < 
 r > < S 
 
 Thickness 
 
 21 SO ft. 
 
 600 ft. 
 
 800 ft 
 
 2 75 ft. 
 
 Character of rock 
 
 Thin bedded blue limestone and calcareous shale 
 intimately interstratiTied. 
 
 Green shale with ferruginous mottling, altered to 
 white shale by hydrothermal action. 
 
 Limestone,more massively bedded than the higher 
 strata, but also interstratified with shale. 
 
 Calcareous shale,generally yellowish. 
 
 Thin bedded blue limestone and shale overly!ng cal¬ 
 
 careous sandstone which is anarkose next to the diorite. 
 
 Diorite 
 
 PfP 1 
 
 Timmito 
 
 H// 
 
 
 * ~n . 
 
 * " 2 .. , 
 ❖ V -iv >N ' 
 
 Andesite dikes 
 
 Basic eruptives (Pre-Cretaceous) 
 
 Faults 
 
 Tis* 
 
 Massive,brown limestone 
 
 'SED IN THE QUEBRADA ASIENTOS, POTRER1LLOS 
 

 
 
 
 
 
 
 
 
 
 
 
 - 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ■ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Investigation of the Earthquake Mechanism 
 
 75 
 
 In the region north of Coquimbo and La Serena the minor thrusts constitute a 
 parallel system and occupy a zone about ioo miles (160 km.) wide, so far as is known. 
 In this zone 14 of them have been identified. There may be others within it, and there 
 certainly are others to the east of it in the more inaccessible districts of the high pla¬ 
 teau. This system of parallel minor thrusts trends north-northeast and extends be¬ 
 yond the limits of my observations in the Andean plateau. At its southern end it 
 changes its course, but I was unable to satisfy myself definitely regarding the continu¬ 
 ation of the faults. They may swing out toward the southwest and pass out under the 
 ocean, as I had at first supposed from the suggestions of the landscape near Coquimbo 
 and because of the distribution of earthquake intensities, which die out abruptly south 
 of that place. But there are some indications in the trends of the ranges and valleys 
 which afterward led me to think that the fault system south of Coquimbo may turn 
 south-southeast, and might extend through the great heights of the Cordillera to the 
 vicinity of Santiago and beyond. The question remains altogether indeterminate 
 for lack of time to pursue the studies in the stretch of 250 miles (400 km.) between 
 Coquimbo and Santiago and because exploration in the heights of the Andes is im¬ 
 practicable in winter. 
 
 The recognition of this unexpected relation between earthquakes and thrusts 
 of the Highland type does not modify the concept of an earthquake as an effect of 
 elastic rebound. It merely supplements the observations made in 1906 in California, 
 which established that explanation as the correct one. It connects the rebound, how¬ 
 ever, with flat-lying thrusts which were not previously known in an active state, and 
 thus advances our understanding of the possible conditions under which earth¬ 
 quakes may develop. 
 
 EVIDENCES OF PRESSURE 
 
 General Statement 
 
 The elevation of the Andes is in itself evidence of pressure exerted from one or 
 both sides of the mountain range to uplift the corresponding zone of the earth’s crust. 
 Our knowledge of the mountain chains of the world, and particularly of coastal 
 ranges, leads us to anticipate that we would find in such a cordillera evidence of 
 severe compression expressed in the jointing of all massive rocks and the folding of 
 stratified beds. Such is, indeed, the fact. Wherever one goes, whether in the coast 
 range of Chile or in the Andes themselves,’ all classes of rocks exhibit jointing and 
 marine sediments are uptilted, folded and also repeatedly overthrust. The facts of 
 jointing and folding have often been noted, but the evidence of overthrusts, although 
 perhaps observed, has, so far as I know, not hitherto been published. 
 
 Overthrusts at Potrerillos 
 
 Potrerillos is situated in the Andes, in latitude 26° 30', 80 miles east of the port 
 of Chanaral, at an altitude of 10,400 feet (3,100 meters) at the mining camp and 
 12,000 to 14,000 feet (3,500 to 4,000 meters) above sea in the mountains in which 
 the mine itself is situated. The mining camp is located on a broad gravel slope, the 
 upper part of the old valley floor of the Rio Sal and its tributaries. In this slope a 
 
76 
 
 Earthquake Conditions in Chile 
 
 canyon 1,500 feet (450 meters) deep has been cut by a stream that flows from the 
 eastern heights westward and passes north of the camp to join the Rio Sal somewhat 
 lower down. In this canyon the rocks are well exposed, and it is there that overthrusts 
 were first seen in the course of my studies. The upper part of the canyon, to which 
 we shall chiefly refer, is known as the Ouebrada Asientos or Asientos Gulch. 
 
 The rocks of the region comprise (a) granite or diorite of pre-Jurassic age; 
 (b) Jurassic or lower Cretaceous (Comanche, Neocomian) shales and limestones, 
 which rest unconformably upon the granite; (c) rhyolite and andesite dikes; and ( d ) 
 younger volcanics. The field relations show that the granite and marine shales and 
 limestones are older than the faulting, whereas all the later igneous rocks are younger. 
 Thus the faulting is placed in the Tertiary and may be regarded as pre-Pliocene. 
 
 The section that I studied in detail may be observed in Asientos Gulch, between 
 Montandon station of the Potrerillos railway and a point some 10 miles (16 km.) up 
 the canyon. The traverse of the canyon and the observed structural facts are given 
 in Plate XLII, which is drawn according to a paced traverse oriented by compass 
 sights. 
 
 The relation of the upper Jurassic (Tithon) limestones and shales to the granite 
 is the first item in the geologic record to be established, especially because it is not 
 the same as that of the granite at Chuquicamata and farther north in Peru, as de¬ 
 scribed by Lindgren. 1 In that northern region the granite is intrusive in lower Cre¬ 
 taceous limestones, as is demonstrated by the contact metamorphism of fossiliferous 
 beds. At Potrerillos the unconformable contact of the upper Jurassic terrane with 
 the granite can be observed immediately below Montandon station and again 10 miles 
 up Asientos Gulch, at both ends of the section. In each locality the dip is in the neigh¬ 
 borhood of 20 0 toward the west. The basal strata of the sedimentary series in con¬ 
 tact with the granite are arkose sandstones derived from the underlying massive rock 
 by weathering, and the fact of unconformable deposition is clearly demonstrated. 
 The sequence of sediments upward from the base consists of thin limestone strata 
 alternating with earthy shales, which vary in color from the predominant yellow beds 
 to green and red. The total thickness of the series is probably 2,000 feet, but it is 
 difficult to be precise, because the strata are frequently repeated in the section with 
 isoclinal dips. Although the degree of dip varies from 5° to 8o°, it is neverthe¬ 
 less so persistently inclined down toward the west, that one gets the impression of a 
 continuous conformable sedimentary series in the first examination of the Asientos 
 section. A careful reconstruction of the structure, on this assumption, showed that 
 the shale and limestone series would have the preposterous thickness of 30,000 feet 
 (9,000 meters). This impossible result confirmed the inference, which I had drawn 
 from preliminary observations, that the series was repeated by overthrusts. It was 
 not, however, until I had passed over the section three different times that I realized 
 how numerous the thrust faults are, and I am not sure that the seven which I identi¬ 
 fied in the 10-mile section represent the total number. 
 
 1 Personal communication. 
 
Investigation of the Earthquake Mechanism 
 
 77 
 
 The criteria used to identify the locations of thrust faults were: 
 
 (a) The abrupt termination of limestone cliffs. As may be seen in the photo¬ 
 graphs, the limestone ledges contour the walls of the canyon, rising with the dip from 
 the bottom of the gulch to some more or less distant point, where they terminate in a 
 talus slope. The latter consists of fragments of crushed limestone and shale. Near 
 their end, that is, immediately above the fault, the strata are sometimes abruptly over¬ 
 turned, but not infrequently there is no change of dip, even where the juxtaposition of 
 unlike strata shows that there is a fault between them. 
 
 ( b ) The overturned dips just referred to. These are most commonly seen where 
 the thinner beds of limestone are caught immediately above the thrust. Where the 
 latter traverses the shales the fracturing has been so great that it is completely buried 
 in talus, and where it cuts through the heavier limestone beds they have been too rigid 
 to be bent over by the friction on the fault plane. 
 
 (c) The sudden steepening of the western dip, a peculiar feature, which I came 
 to recognize as evidence of the location of a thrust. This effect is found immedi¬ 
 ately above the thrust plane and is the reverse of what we ordinarily expect, for we 
 commonly consider only the forward overturned limb of an anticline in relation to 
 the thrust plane. If, however, we prolong the latter downward across the anticlinal 
 axis, it passes under the adjacent syncline, the advanced limb of which is not infre¬ 
 quently bent backward so that it has a very much steeper dip than the limb through 
 which the pressure is being transmitted. This relation is a common one in Asientos 
 Gulch and may perhaps be better understood by reference to the section. 
 
 ( d ) The repetition of beds is one of the best evidences of thrust faulting, pro¬ 
 vided there is some distinctive key bed or other criterion by which one may be sure 
 that an apparent duplication by faulting is not in fact a repetition of similar sediments 
 of different horizons. In studying the section of Asientos Gulch, I found the base of 
 the sedimentary series only at the two ends, where the strata rested on the granite, 
 as described, but in the sequence above the immediate base there was a mass of green 
 shale which did not seem to be repeated at higher horizons in the regular sequence 
 and which I regarded as duplicated by faulting where it occurred in other parts of 
 the section. There were two massive limestone beds separated by a thin shale stratum, 
 and also a heavier mass of limestone which I thought I could identify in the higher 
 portions of the section. These were used as key horizons. 
 
 (e) The strata are greatly altered in places on the fault planes, and consider¬ 
 able masses of ferruginous spring deposits occur on the outcrops of the fault. Where 
 this occurs the fault plane is completely obscured and the inference has to be based 
 upon the occurrence of the spring deposit, although it may be confirmed by dupli¬ 
 cation of the strata or other structural evidences at a little distance from the plane. 
 
 (/) At various points the fault planes otherwise identified as such by the evi¬ 
 dences already described are found to have been occupied by intrusions of rhyolite 
 or andesite. In following out such a fault it is, then, reasonable to infer that it exists 
 where andesite dikes occur in the proper orientation along the strike. While it is true 
 that there are other structures, such as persistent joints, transverse faults, or irregu- 
 
78 
 
 Earthquake Conditions in Chile 
 
 lar fractures, which have guided molten intrusives in their course toward the sur¬ 
 face, yet it is a fact that thrust faults have frequently acted as the planes of weak¬ 
 ness which have directed the movements of such masses. This phenomeon is so 
 marked that there is reason to consider the thrust faults as the principal structural 
 condition which has determined the location of ore-bearing, intrusive masses in the 
 coast ranges and Andes of Chile. 
 
 Through the application of the above-cited criteria, seven thrusts were identi¬ 
 fied in the io-mile section of Asientos Gulch. They are shown in the accompanying 
 drawing (Plate XLII) and require no special description beyond what has already 
 been stated. Their dip is westward and varies from 35 0 to 65°. They are accompa¬ 
 nied by a great deal of fracturing, and this fact, taken in connection with the high 
 dip that many of them exhibit, indicates that the strata were not heavily loaded. In 
 that part of the section which we now see these thrusts were approaching the surface. 
 They undoubtedly extended to it at the time of their development. 
 
 These relations are interestingly illustrated in the structural relations of Potre- 
 rillos copper deposits. The copper occurs disseminated in a body of monzonite por¬ 
 phyry which is intruded into faulted limestones and shales. The geographic relation 
 of the ore deposit to the system of thrusts identified in Asientos Gulch is such that 
 thrust-planes pass on both sides of the mine and one would pass through it if its posi¬ 
 tion had not been taken by the intrusive porphyry. 
 
 One of the upper thrusts of the Asientos series is characterized by intrusions 
 of andesite. Followed along the strike with appropriate allowance for dip and differ¬ 
 ence of elevation, this thrust can be traced west of the ore deposit, where andesite 
 again occurs along it. Another thrust, which crosses Asientos Gulch at Cachiyuyu 
 Spring and the line of which is closely followed by the trail from Cachiyuyu Spring 
 to Potrerillos mine, passes east of the mine through Potrerillos Gap. Between these 
 two thrusts, which can be traced respectively west and east of the mine, there are 
 three other thrust faults and the ore-body lies on one or more of them. Since the 
 copper-bearing rock is an intrusive porphyry, and since the thrusts have guided other 
 intrusives, a genetic relation between the porphyry and the thrusts on the strike of 
 which it occurs is strongly suggested, and there are also local conditions at the mine 
 which explain the volume and form of the particular deposit. These consist in the 
 strike and dip of the overlying limestone described in the next paragraph. 
 
 One of the heavier beds of upper Jurassic limestone lies above the Potrerillos 
 ore-body, but not immediately upon it. The intervening space is occupied by shale. 
 The limestone northwest of the mine has the usual strike of the series, about N. 25 0 E., 
 and dips to the west. In approaching the mine it bends sharply toward the southeast 
 and east and takes on a steeper dip. This is the overturn which characterizes folded 
 strata immediately above a thrust fault, but in this case the pitch of the overfold is 
 very steep and the fold plunges abruptly toward the southwest. It is plain that the dis¬ 
 location was caused by pressure from the northwest, was accompanied by horizontal 
 movement and dragged the edge of the limestone over. 
 
Investigation of the Earthquake Mechanism 
 
 79 
 
 This effect may be simulated by placing the finger-tips of the right hand on the 
 palm of the left hand and moving the right hand forward over the left. It will be 
 seen that the fingers of the right hand bend and a hollow is formed between the 
 palms. The palm of the left hand represents the thrust plane, while the right hand 
 is the limestone stratum. 
 
 As has already been indicated, there is evidence in the fractured and open con¬ 
 dition of the strata next to the fault plane that the limestone bed at the Potrerillos 
 mine was competent to lift some part or all of the superincumbent load as it arched 
 up in dragging along the fault plane. The result was that the shales underneath it 
 were loosened and space was provided for the intrusion of the porphyry. The latter, 
 rising on the fault plane in its deeper extension, reached the cavity and assumed 
 the pear-shaped form which was determined by the bending of the competent 
 limestone. 
 
 These facts seem to bear very directly upon the form and size of the ore-body. 
 The fold within which it is located is a local feature, but is one of such size that it 
 gives reason to expect a large and rather deep hollow within the arch. The thicker 
 rounded portion of the intrusion would occupy the higher southwestern part of the 
 arch, while the porphyry mass would thin out toward the north in a horizontal section 
 and also in depth in a vertical section where the limestone approaches the thrust plane. 
 The foot-wall of the ore-body would be flat and the hanging-wall concave down¬ 
 ward. It would have been advantageous had the mechanical structure of the ore-body 
 been understood at the time that it was drilled to determine the amount of the ore 
 reserves, but at that time the existence of the thrusts had not been recognized and 
 the interpretation of the mechanics of intrusion had not been suggested. 
 
 Structural Conditions at Chuquicamata 
 
 Chuquicamata is situated in latitude 22 0 18' south, about 85 miles (135 km.) east 
 of the coast of Chile at Tocopilla, and at an altitude of about 10,000 feet above sea 
 (3,000 meters). In the accidental relations of distance from the coast and altitude, 
 Chuquicamata and Potrerillos, the two great mining camps, are similarly placed, but 
 there is otherwise very little resemblance between them in their topographic situation. 
 Potrerillos lies near the summits of high mountains, Chuquicamata on the side of a 
 broad valley. 
 
 Coming north by rail, one gets out at the station Calama and drives by automo¬ 
 bile some 10 miles (16 km.) north to the mining camp of Chuquicamata. The road 
 skirts the foothills of a range of mountains on the northwestern side of the valley, and 
 ascends a long alluvial slope which occupies a reentrant angle between the mountain 
 spurs. The hills are rounded, their bases are buried in wash, and the aspect of the 
 landscape is that of the matureland which is so widely recognizable as the oldest 
 topographic feature of the Andes. One may note immediately that the profiles of the 
 mountains descend toward the valley and pass under it in such manner that the low¬ 
 est of the foothills form peninsulas and others project like islands out in the valley 
 floor. The first impression, which was subsequently confirmed by more extended 
 
80 
 
 Earthquake Conditions in Chile 
 
 observation, was that the valley is one of those downwarps or synclinal depressions 
 beneath which the old matureland lies buried in the debris of later cycles of erosion. 
 The maturity of the landscape has a bearing upon the enrichment of the copper de¬ 
 posits, as will appear later. 
 
 The ore deposit at Chuquicamata is a mass of crushed granite, which forms the 
 floor of the wide reentrant angle in the foothills and of the low pass in which the 
 angle ends. It is obvious that the angle in the hills was eroded because of the crushed 
 condition of the granite, which rendered it relatively weak in contrast to the some¬ 
 what more massive rock of the spurs on either side of it. Thus the ore deposit is 
 related to a mechanical condition of the rock which is expressed in the topography. 
 
 I was looking for physiographic evidences of thrust faults such as had been 
 found at Potrerillos, but they were not to be detected in these long, debris-covered 
 slopes. The thrusts are there, but they were not to be seen, because erosion had com¬ 
 pletely obliterated all surface evidence. 
 
 By courtesy of the Andes Copper Company, I was enabled, during my three 
 day’s stay at Chuquicamata, not only to examine the mine, but to ride far afield, and 
 was accompanied by A. B. Motta, the resident geologist. I was furnished with the 
 unpublished report by Lindgren on the geology of the mine, and Mr. Motta gave me 
 all the information which his familiarity with the ore deposit could make available. 
 
 The primary object of my studies was to detect any evidence of overthrusts 
 which might be connected with the earthquakes occasionally felt at Chuquicamata. 
 Since the general structural trends of the region as manifested in the synclinal valley 
 and the mountain ranges are northeast and southwest, I inferred that any overthrust 
 structure might be crossed in going northwest. Accordingly, in our first ride 
 Mr. Motta and I went north to Aralar, some 16 miles (25 km.) from Chuquicamata, 
 and then rode in a wide circuit toward the west and south till w T e struck the Tocopilla 
 road, by which we returned. Our route took us up over the mountains back of Chuqui¬ 
 camata and down into other basins which are widely filled with debris and every¬ 
 where show the characteristic features of the Andean matureland. The landscape 
 lacks structural expression; that is to say, elevations or depressions caused by fault¬ 
 ing have been so deeply eroded in the one case or filled in the other that their struc¬ 
 tural origin is obliterated. Certain long, straight lines of hills suggested faulting of 
 one type or another; but on the whole the observations of that first day were incon¬ 
 clusive, since the evidence was not of a kind to demonstrate the fact of faulting. 
 
 In returning along the Tocopilla road, at a high point 7 miles (11 km.) west of 
 Chuquicamata, I observed that we were riding on granite which formed the ridge 
 top, whereas the ravines were cut through the granite into red and green sedimen¬ 
 tary rocks which had a strike of N. 20° E. magnetic and dipped 50° northwest. 
 Answering my question as to the relation of the higher granite to the underlying 
 sedimentaries, Motta said the granite was intrusive in the sedimentaries and that the 
 latter in this locality formed an included mass. He justified his explanation by the 
 fact that elsewhere the granite is seen to be intrusive in fossiliferous sediments, and 
 the intrusive character is clearly demonstrated by the contact metamorphism of the 
 
Investigation of the Earthquake Mechanism 
 
 81 
 
 limestone. This fact had been established by Lindgren and is one of the well- 
 established conditions of the geologic sequence. It was therefore most natural to 
 assume that the same condition existed at the locality over which we were passing. 
 
 On the following day we returned to the point on the Tocopilla road where the 
 granite may be seen overlying sediments, and made a careful examination of the 
 contact, together with a transit survey by which to determine the form of the contact- 
 surface. We found that the sediments are not metamorphosed in this locality; that 
 there are no dikes of granite penetrating them. There was therefore no evidence 
 of the intrusion of the granite into the sediments nor of the inclusion of the mass of 
 sediments in the granite. By means of the transit survey by which the relative eleva¬ 
 tions and horizontal positions of five points on the contact were determined over a dis¬ 
 tance of 600 meters, it was found that the surface of contact between the underlying 
 sediments and the overlying granite was a nearly flat plane having a strike of N. 16 0 , 
 
 17 0 , or 24° E., according to three different solutions of the graphic problem, and a dip 
 of 8° toward the north of west. The variations in the several determinations of 
 strike are such as might be expected, since the exact position of the contact-plane 
 could not be observed because of the talus on the slopes, and the plane itself is prob¬ 
 ably not perfectly flat. The form of the surface and its attitude correspond with those 
 of a flat-lying shear plane, and, in view of the fact that the evidences of an intrusive 
 contact were entirely lacking, it was clear that we had to deal with such a thrust. 
 
 The fact of the occurrence of overthrust faulting in the vicinity of Chuquica- 
 mata having thus been established, the purpose of my visit was accomplished, so far 
 as the earthquake study was concerned; but I was interested to ascertain to what 
 extent, if at all, the ore deposit owed its existence to these thrust faults. I therefore 
 made a study of the jointing of the granite, with a view to ascertaining the direction 
 of the pressures which had crushed it, and took observations of the direction of 
 striation on the footwall fault as an indication of the direction of movement of the 
 mass. The general conclusions are as follows. 
 
 The crushed mass of granite which constitutes the ore-bearing rock of Chuqui- 
 camata lies between a major thrust fault, whose general strike is about N. 20° E. and 
 which dips very steeply, probably 8o° or more, toward the west, and a branch of that 
 fault which strikes west of north and thus forms an acute angle with it. The major 
 thrust is the hanging-wall, the minor thrust the foot-wall. Neither of them is very 
 well defined, as they are zones of crushing which developed near the surface rather 
 than clean-cut, deep-seated shears. They serve, however, to delimit the ore-body. 
 
 The foot-wall forms an acute angle with the hanging-wall, both in plan and in 
 section. The mass between them is therefore wedge-shaped and the edge of the wedge 
 points northeast and pitches steeply southwest. The latter is the direction in which the 
 mountain spurs on either side open out toward the valley. The stride observed on the 
 fault surfaces of the foot-wall are gently inclined. They rise at an angle of 12 0 to 18 0 
 toward the southwest. Thus the movement on these planes has been outward and up ¬ 
 ward from the northeast toward the southwest; that is to say, the whole mass of shat¬ 
 tered granite has been squeezed out between the two faults in the direction in which 
 
82 
 
 Earthquake Conditions in Chii.e 
 
 a wedge of that particular form would move under the great compressive stresses 
 which caused movement on the thrust-planes. 
 
 With this general concept in mind, we may essay to trace the steps of concen¬ 
 tration of the copper minerals. Lindgren reached the conclusion that the copper was 
 indigenous to the granite, and I see no reason to question the correctness of that view. 
 Lindgren also determined that the granite is intrusive in early Cretaceous limestone, 
 and we may note in passing that it is therefore younger than the pre-Jurassic granite 
 of Potrerillos. 
 
 At some time during the Tertiary the region was subjected to compressive oro- 
 genic stresses, which resulted in shearing the massive granite and overthrust it. It 
 is apparent from the attitude of the thrust plane on the Tocopilla road that those 
 pressures came from a direction of west-by-north, but the major thrust, which is the 
 hanging-wall of Chuquicamata, was a steep upthrust, not a flat-lying thrust plane 
 like that which we measured. 
 
 The development of a minor branch fault in front of a steep upthrust is a 
 mechanical result which we have observed in the similar structures in California and 
 which is readily explained according to mechanical principles. Thus the foot-wall 
 fault of the ore-body is genetically connected with the hanging-wall fault. 
 
 The episode of active faulting undoubtedly gave rise to the major features of 
 the topography in the vicinity of Chuquicamata, but it was followed by less active 
 displacements on the fault planes and by the erosion of fault scarps to the point where 
 they are not readily recognizable as such in the landscape. 
 
 The wedge-shaped mass contained between the hanging-wall and the foot-wall 
 was completely shattered, as is evident from the jointing by which it is now traversed. 
 In this shattered condition it was peculiarly liable to percolation by atmospheric 
 waters, and the copper minerals contained in the granite were superficially dissolved 
 during the prolonged period of erosion that followed the active faulting. Thus the 
 deeper portions of the shattered ridge were secondarily enriched, as they are now 
 found to be. The copper minerals at Chuquicamata are carbonates and secondary 
 sulphides which are concentrated upon the joint planes of the crushed granite. 
 
 The percolation of the atmospheric waters that accomplished the concentra¬ 
 tion appears to have been facilitated by the opening up of the wedge of granite as it 
 was squeezed upward and toward the southwest. That this was the direction and 
 effect of movement is evident on examination of the striae on the fault planes. It is 
 clear that the squeezing-out of the wedge was made possible by the fact that it lay 
 immediately beneath the surface, under little or no load of superincumbent rock, and 
 also that it came in time, as the Calama valley developed, to lie on the hillside above 
 that valley in a position in which it met with no resistance as its mass moved in a 
 southwesterly direction. It is thus evident that this great ore-deposit owes its 
 existence as a concentrated ore-body chiefly to those mechanical conditions of struc¬ 
 ture which have facilitated the entrance of atmospheric waters to the innumerable 
 joint fissures in the copper-bearing granite. 
 
Events of Post-Cretaceous Time 
 
 83 
 
 EVENTS OF POST-CRETACEOUS TIME 
 PHYSIOGRAPHIC INTERPRETATION 
 
 The facts of geologic history, so far as they can be read in the rocks of central 
 Chile, are restricted to the ages before the close of the Cretaceous. The beginning, 
 like the beginning of human histories, is lost in the mists of the past. Some ancient 
 sedimentary rocks, believed to be of late Paleozoic age, are intruded and metamor¬ 
 phosed by granite. The intrusion has destroyed all earlier evidence, except the fact 
 that limestones and clastic sediments had been deposited along a coast in this vicinity 
 when the eruptions appeared. 
 
 From that event on through the Mesozoic age the record of changing conditions 
 is found in continental sediments of the Triassic, in marine sediments of the Jurassic, 
 which are associated on a large scale with basic lava flows, and in Cretaceous marine 
 sediments. These rocks are sufficiently described in the chapter on the geology by 
 Dr. Felsch and in the geologic notes. 
 
 The Cretaceous strata occur in the heights of the Andes and are of Neocomian, 
 lower Cretaceous age. From then on to the present the marine record fails, except in 
 the case of the Pliocene and Pleistocene deposits of Coquimbo Bay. We are thus 
 thrown back upon the records made by subaerial agencies, which are written in what 
 we may call physiographic script. I use the word script designedly to express the 
 idea that the post-Cretaceous history is written in the landscape, in the forms of the 
 mountains and of the valleys engraved on the surface of the land. 
 
 The record is made by winds and waters which sculpture more or less elevated 
 lands, according to their elevation above sea, the inclination of the surfaces, and the 
 climatic conditions. In general, the elevation of the land mass is that condition which 
 determines its physiographic expression. If the mass is being actively upraised, the 
 features sculptured upon it are young canyons, whereas if it has for a long time stood 
 nearly at the same level the sculptured forms will have reached maturity. These 
 terms signifying youth and maturity are here used in a broad general sense, as apply¬ 
 ing to the features of a landscape during a considerable lapse of time in either case. 
 There are a great many lands of youthful topographic aspect, that is, lands which 
 exhibit the effects of recent sculpture by streams. They are cut by canyons of greater 
 or less depth and more or less precipitous walls, between which extend surfaces that 
 invariably present an older aspect. A young landscape is therefore a composite in 
 that the youthful canyons are associated with older surfaces which owe their forms 
 to some previous stage of elevation. 
 
 Maturity, on the other hand, when applied to the landscape, describes a phase 
 which has been reached as the result of prolonged erosion, without material change 
 of elevation except in so far as the height of the land surface above sea has been 
 lowered by degradation. In maturity a landscape is simple, not composite, all of tbe 
 features belonging to one and the same phase of sculpture. Maturity is reached when 
 youthful canyons have widened to valleys and valleys to broad flood plains; and when 
 
 9 
 
84 
 
 Earthquake Conditions in Chile 
 
 the interstream areas, which in the youthful stage exhibit the features of an older 
 topography, have been reduced to sharp divides in which that older stage can no 
 longer be identified. 
 
 In the effort to reach precise definitions, youth, adolescence, maturity and old 
 age, as applied to topographic forms, have sometimes been given more exact charac¬ 
 teristics than those implied in the preceding general description. An effort is made 
 to fix the exact instant or the precise form in which one phase passes into the next. 
 But such refinements are not practicable where one is dealing with a great variety 
 of conditions and resulting forms. The terms are therefore used in a broad descrip¬ 
 tive sense in this report, as indicated above. 
 
 Physiographers have long since become accustomed to the use of the terms intro¬ 
 duced by Powell, Gilbert, and Davis to describe the conditions of a land surface which 
 had reached extreme old age, namely, base-level plain or peneplain. The older term, 
 base-level plain, once covered the condition described by peneplain, but the latter was 
 coined to describe surfaces which, though advanced toward the ultimate stages of 
 erosion, still retain a degree of relief inconsistent with the idea of a base-level or 
 grade plain. The latter term has almost gone out of use, except as a theoretical con¬ 
 cept. Peneplain, on the other hand, has been stretched in application to designate 
 surfaces where the relief was still so great that the term plain could in no sense be 
 applied to them. This misuse of the term has been particularly conspicuous in the 
 writings of those who have described Pacific Coast landscapes, and arises from the 
 fact that there are no peneplains in the mountains around the Pacific, while yet there 
 are old surfaces for which some designation is required. These surfaces present 
 features of mature topography, often of advanced maturity, but rarely, if ever, of 
 that extreme age to which the term peneplain may properly be given. In describing 
 these mature landscapes of Pacific regions, I find it convenient to use the word 
 matureland, which will appear frequently in the sequel. 
 
 As already indicated, the distinction between the term peneplain and a mature- 
 land is one which has a regional distribution. Remnants of peneplains can be identi¬ 
 fied in North America and northern Europe, on both sides of the Atlantic, and it is 
 there that the term has found its proper application. The fact follows naturally from 
 the inactivity of orogenic forces around the north Atlantic basin since the Triassic. 
 During the Jurassic and Cretaceous periods eastern North America and Europe 
 were reduced by erosion to a very low level. By the close of the Cretaceous a pene¬ 
 plain was very widely developed and it was extended during the early Tertiary. Since 
 the Miocene there has been a gradual elevation and the peneplain has been eroded, 
 but not destroyed beyond recognition. 
 
 Lands around the Pacific, on the contrary, have not come to rest for a time suffi¬ 
 cient to develop a peneplain landscape at any time in their recorded histories. Possibly 
 the late Carboniferous seas, in which the sediments appear to have been predomi¬ 
 nantly calcareous, may have been bordered by extensive plains. But local intrusions 
 

Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLIII 
 
 A. Salar de Infieles. Salt basin on fault zone northeast of Potrerillos; elevation about 13,000 
 feet (4,000 meters) ; Cerro de Infieles (16,570 feet), looking north. 
 
 B. Salar de Pedernales. Large salt basin occupying wide valley in Andean plateau, northwest of 
 Potrerillos; elevations 11,500 to 13.000 feet (3,500 to 4,000 meters) looking south. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLIV 
 
 A. Potrerillos (matureland northeast of). 11,500 to 13,000 feet above sea; Pliocene (?) volcano, 
 
 Dona Ynez, 16,630 feet (5.070 meters), in left center. 
 
 B. Potrerillos, Quebrada Asientos. Fringing gravels, cemented; elevation 10,000 feet 
 
 (3,000 meters). 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLV A 
 
 710° 
 
 Clqmque 
 
 21 ° 
 
 Ap.de Si iliMica"74650 
 
 S.de Huasdo^ ' r 
 C.Guai'l la f A-.fi 
 
 r^’ C.Napa;°A 
 Pintados 5lf4£^ 
 
 C.lrruputuncu d Embexa 
 
 15165 \ 
 
 IF 
 
 IF 
 
 \ 5200 
 
 oUyuni AC.Ubina 
 
 4800AC.Tasna 
 
 w \ 
 
 c .°lca7A . 
 
 v‘ 
 
 ) 
 
 C 44001 ^ 
 
 C.ChocayaA oAtocha 
 
 C.Auncanquilcha A 
 6180 ) 
 
 
 £ 
 
 
 C. Palpana A 
 6040 ' 
 
 $ 
 
 C.Colcha 
 
 l 
 
 ) 
 
 m ~S.de T A } | 
 
 Chiguanar-s C.Caiuincha 4800 ' r . 
 5 II 3^ a ~- 3 0 J AC.Lupijara 
 
 C. Escapa j 07 4400 ''oSanVicente 
 
 21 ' 
 
 r\ 
 
 ( 
 
 \ 
 
 •37-an A E.A^uasCalientes ^ 
 
 3730A o \ cs 
 ASCOtac'C^ / \ \ \ 
 
 / 
 
 \ 
 
 SieoP-S^'zabel 
 "”Ooan Fbblo 
 ij^C.Bonete 
 
 oTupiza 
 
 22 ° 
 
 0 
 
 )Toco]jilIa 
 
 O 
 
 M§ Je Cablor 
 Op. v ( j e oCalama 445f f 
 y^Hfiraje C.Chuschul a 404 0 
 
 -« 4 -fi ui p e ‘ 5 ^ CMorocol 
 
 C.deJorcadaj£Sonequer^ ^ Upez ' oS f ntaCatahna 
 
 V 1 ? LinzorA 5820 ,-P "PSPJuan -^ 444 n er \ C0 
 
 5560' ftC.Uturunco/ .. - « « ' > 4440 
 
 w i \- 
 
 -^Port.de^PanizoV ’ - 
 \ 51 00 c? 5650 A^. LorbWl^y 
 
 A. 
 
 / 
 
 San Pedro de Atacama o 
 
 !vO 
 
 5370 v 
 
 I SOJuan 
 " o O , 
 
 . A -AC.Li mitado 
 
 » I 
 
 /, 
 
 0 / 
 
 
 b- 
 
 CChajnatopA 
 
 5930 fi^ C.Sapaleri A 
 C.Lincabur 
 
 \ 
 
 <? 
 
 AC.Escaya 
 
 4369 
 
 ° ^inconada 
 
 J 
 
 )Meji]lono^ 
 
 Ant ofa casta 
 0 
 
 
 C.Quimal a4260 
 
 < o/ 
 
 C.l 
 
 V— 
 
 ( r 530 X cfAy dSario 
 ) z 
 
 / i 
 
 /AC.Totay / 
 4365 J / 
 
 / 
 
 0 °a 5400 
 a _ ^ C.lncahuasi 
 
 W V 
 
 Jfr 4560 ^ 9 ; de 
 / Bavaro 
 
 Trds Cruces 
 
 >£ 1 
 Puntas ^5770 2 
 
 Negras A5890 
 
 I 
 
 ' ^cr 1 
 C.lncahuasi 
 
 C.del 
 
 A 5594 
 
 mlac A 
 Q ' 
 
 Solar de t 
 PuntaNecg-a 
 
 VPS 
 
 o com pa ^03, 
 
 r<y 
 
 25 ° 
 
 JC Tall;d 
 
 A, 
 
 C. Guanaca A 
 dJ 
 
 C.Punta de! Viento ^4600 
 
 Q 1 
 / 
 or/ 
 
 4 / 0 ) 
 
 C.del Bolson A / 
 4900 I 
 U I 
 
 .A L^- 
 
 VPLlulia’/llaco 
 
 C 48 i 
 
 a 
 
 ' i 
 
 J 
 
 02 
 
 V UJ 
 
 6 
 
 24 
 
 5 Z 90 ^CTultul 
 Uj 
 
 I , I 
 
 Rincon J i SPAntonio vde 
 , 50500 I OS Cob 
 uC ChoriMos 
 
 res 
 
 Antofal la 
 oj 
 
 / . 0 A"" 
 
 '•V. Antofal la 
 
 S’, de Fed email’s / 
 
 >Chanaral 
 
 4 
 
 ( 
 
 5 
 
 \ 
 
 ! 
 
 I 
 
 / 
 
 fit' 
 
 -\ 
 
 Q\ 
 
 02 
 
 1 
 
 oO/ 
 O / 7 
 
 ^CAufoe 634 ^^ 1 ^ 
 
 " Rosa \/ 
 
 5200AC.Pircas 
 
 J oPoma Salta 
 
 _i 6500 o 
 
 C.Mojon Blartfo ^ A N 5 o d o e ^hi Rosan - 0 ^ eLfirm ^ 
 
 - '■ ( 75250 ° CaChi 
 
 *. AC.Tagarume 
 
 Muerto oMelinos 
 l 
 
 C.Bravos A 
 
 jb Crddera 
 Copiapoo 
 
 ) 
 
 “5280 l 
 V l. 
 
 )j 
 
 \ ' 640 CA S - Nevada C? 
 
 L -AV-Sarm iento 
 
 \ 
 
 \ 
 
 \ 
 
 . :<</, r 5500 C.Galan 
 Antofagasta - A - 7 
 
 0 7 ^Sierra / C.Leon Muerto 
 
 * | 
 
 ^ I 
 
 oSan Carlos 
 oCafayate 
 
 / 
 
 / 
 
 6300 ^^ 7 ^° 4200 r , 
 
 ’ ^ 5850 A C^e^ro . SdAb.deVentura 
 
 x? 93 ° j 7 uertox ^r aAuI 
 ^ -^6020 ‘t 5060 ddTh zu !, 
 
 4795 tC SP Francisco t 
 
 4960 /■ 
 C.Ojo de Maricunga 
 
 S ‘-^ 6356 ,'^--' 
 
 O Santa Maria 
 Tucuinan o 
 
 27 ° 
 
 / N?deTres CrucesC 
 
 /V I C ^ ^ 
 
 C.Copiapo A 6080 ; 6493 AC.deI Nacimiento 
 < / A 2 
 
 C. Paredomes a ^ 5 
 
 6(7° 
 
 / 
 
 / 
 
 Port, de Arr. Panq^pa ^ 80 
 C.Vidal Gormaz'X 5900 
 
 i i 
 
 14500 ) 
 
 Vt: 
 
 28° 
 
 7|0° 
 
 2 
 < 
 
 Port.de 
 los Aparejos 
 
 ^ '' ' Fiambala , O 
 
 ! 5800C.Punilla 
 
 ^A 5060 o 2 g= 
 
 C AWo ,do cjsy_Tinogastao 
 
 Salars 
 
 Divides 
 
 
 SCALES- 
 
 Passes X 
 
 - Peaks a 
 
 (Heights in meters) 
 
 0 20 40 60 80 MILES 
 
 I-T-^-T e -1 ‘l I 1 V — 1 I ‘| l‘ , * 
 
 0 20 40 60 80 100 120 KILOMETERS 
 
 Desert and Puna of Atacama (after Bowman). 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLV B 
 
 
 tv/ 
 
 "u. 
 
 Or 
 
 V s 
 
 •22 
 
 Tocopillai 
 
 -24 
 
 -26 
 
 -28 
 
 CaJani 
 
 5 anTedrc 
 deAtacania _. 
 
 r 
 
 / 
 
 fc> (?•' >A |p 
 Ar<$ C0 CO 
 
 # r Jj§£X 
 \Ol £ t y? © <*? c 
 if «f^©\ 8 § 3 y 
 
 /rT-I .. / 4 1c i) vSte/te 
 
 ^ /lama a® p ® stetei. 
 
 rj, . M « o J t® ® ® 
 lupizctx ' N &Sfs3©afV&V) 
 
 X.7 U ( fp> 6j '‘ 
 
 //■' __' /? & >* ®iffSfeD ©\ \j-'\ o ~ 
 
 ^ C’Q^<£wltfW^22-- 
 
 Lnci Quucuca xsf 
 
 Jtyrtti^Wsky' 
 
 hi 
 
 Saiar de p 
 AtpddpuL 
 
 ? / fl 
 
 / I 
 
 / i' 
 
 '•") 
 
 r-i 
 
 \:\ >v 
 
 ^0 
 
 «\ 
 
 <, Upskrit 
 
 i 
 
 M 
 
 . «. u’ ssr* -i 
 
 it.v <y?ra<! 
 
 Jaod&U 
 
 VIA 6 ?,&<S%:*d 
 
 V® 
 
 p) <P 
 
 Urf £/ 
 
 Vtete 
 ted./ 
 
 (•> fri 
 
 
 0 ° \ 
 
 gAntofatfast 
 de la Si err t ' 
 
 26 
 
 ,;>£ Coldera K 
 
 „ ,, c 
 
 |"opia'p« 5 /* x \ 
 
 4 
 
 / 
 
 ♦ 
 
 S' 
 
 0 
 
 Yallenanl i 
 
 I 
 
 Tinogdsia 
 
 Atu 
 
 {Bebeno^ 
 
 1 7 "' \ 
 
 &S«L 
 
 \V 
 
 v ^ 
 
 
 Santiago 
 
 ^stero 
 
 28 
 
 ^n\'" N 
 
 itamc 
 
 T*a 
 
 * 
 
 ( 
 
 ;oqulmlj<j'. 
 
 )/ 
 
 
 'V.A 
 
 An,, 
 
 5 \ c°4 
 
 '9 t r> v3/ ' 
 
 M/ La ,{i Mi« te 
 
 (/<§ 
 
 ( 
 
 % 
 
 1 
 
 70 
 
 v\°t\ = 
 
 y/ teA I ) 
 
 x , mMIi,, % I %\ = 
 
 f \ V V V _. I \ “ 
 
 S'an iJiiak^ 
 
 CordoodV 
 
 / iPV v '" ( B°) s\ 
 
 66° 1 
 
 -/ 
 
 
 ifMli ^o o<: fl an d Belt 
 
 ''mu' 
 
 .Eastern base of mountains 
 
 Salars 
 
 Railways -International boundaries 
 
 40 
 
 80 
 
 120 
 
 160 
 
 200 MILES 
 
 20 0 
 
 1 V 'l r-^i 1 1—S H—i 1 r—S r 1 —i—h H—i i 
 
 20 0 40 80 120 160 200 240 280 320 KILOMETERS 
 
 Puna of Atacama. Pacific slope, plateau of the high cordillera,and woodlands of the eastern slope (after Bowman). 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLVI 
 
 >trerillos. Elevation, 10,400 feet (3,100 meters). Terrace of fringing gravels which slopes down, unbroken to Pueblo Hundido, elevation 
 2,500 feet (790 meters) at the western base of the Andes, 40 miles (60 kilometers) distant. Official photograph Potrerillos Company. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLVII 
 
 Copiapo. W'ind-fretted pebbles from highest terrace west of Paipote in the Copiapo basin. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLVIII 
 
 A. River silt in the Copiapo basin, unusually well jointed for unconsolidated Pleistocene 
 
 deposits. 
 
 B. The Andes, 20 miles southeast of Santiago. Granite pinnacle in center with Jurassic lava 
 
 flows abutting on right. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate XLIX 
 
 A. Huasco valley, 7 miles west of Vallenar. Looking north up longitudinal valley; Coast Range 
 of Paleozoic rocks on left: mantling gravels (Pliocene?) in bluffs. 
 
 B. Rio Huasco (headwaters of). Cliffs of gravel (Pliocene?) above Laguna Grande: height 
 1,000 feet (300 meters) estimated: lower slopes are slides, effect of active fault. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate L 
 
 A. Copiapo valley, near Monte Amargo. Interbedded sands and peat beds in river valley. 
 
 B. Copiapo valley, near Monte Amargo. Peat digging. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LI 
 
 Bed of Potrerillos glacierette, on railroad above mining camp, elevation 11,000 feet (3,300 meters). Official photograph, Potrerillos Company. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate Lll 
 
 
 
 
 
 
 
 
 HiF 
 
 (/) 
 
 o 
 
 <L> 
 
 O 
 
 o 
 
 U 
 
 u 
 
 <v 
 
 z 
 
 U 
 
 <L> 
 
 <5 
 
 u. 
 
 o 
 
 V 
 
 o 
 
 £ 
 
 <D 
 
 <D 
 
 <L> 
 
 .5 
 
 *u 
 
 "Sd 
 
 in 
 
 o 
 
 a; 
 
 rn 
 
 u. 
 
 <L> 
 
 U 
 
 O 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LI 11 
 
 A 
 
 Vallenar. 
 
 Close view of gravels exposed in road-cut. showing steeply inclined stratification. 
 
 B. Quebrada de Hielo, 50 miles northeast of Copiapd. Limestone erratics lying on plain of 
 Tertiary tuff, elevation about 3,600 feet (1,400 meters) ; rocks show glacial striae and indicate 
 former existence of glaciers on high peaks farther east. They may have been transported to their 
 present position by floating ice or by cloudbursts. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LIV 
 
 A. Coquimbo. Looking east from Coquimbo point past La Herradura to Pliocene terraces 
 along Coast Range; jointed Paleozoic granite in foreground. 
 
 B Coquimbo. Looking northwest from Coquimbo point, showing broad, wave-cut bench and 
 
 cliff facing Pacific. 
 
LIBRARY 
 OF THE 
 
 UNIVERSITY Or ILLINOIS 
 
Events of Post-Cretaceous Time 
 
 85 
 
 of granite batholiths at one time or another, from Permian to Jurassic, and the sub¬ 
 sequent activity of orogenic forces, have prevented the erosion of any part of the 
 Pacific Coast to a peneplain condition, so far as the writer has been able to observe 
 or to ascertain. The oldest landscape surfaces present mature topography, that is, 
 they are maturelands. 
 
 The term matureland, as used in this report, is intended to describe a landscape 
 which is characterized by broad valleys, sharp divides, a degree of relief which may 
 amount to several thousand feet, and the survival of acute peaks that rise above the 
 ridges and are mountains of circumdenudation. The degree of relief is not an essen¬ 
 tial characteristic, but the sharpness of divides and the acuteness of peaks are 
 typical. 
 
 With this preface we are prepared to take up the post-Cretaceous history of the 
 Andes of Atacama. 
 
 TERTIARY MATURELAND 
 
 A matureland has been widely recognized in the Andes. It is a general feature 
 of the Cordillera. Bowman described its characteristic aspects as they are to be seen 
 in northern Chile . 1 The following quotations are here pertinent: 
 
 From the earliest descriptions of the mountain chains of the Andes one might suppose that 
 they were as rugged as they are lofty and that great peaks and canyons are the rule. The frontis¬ 
 piece of von Tschudi’s travels in South America is an almost glorious piece of misrepresentation 
 in its attempt to show everything connected with the Andes or its borders in one composite view. 2 
 This is not to say that canyons and peaks are lacking. Some of them are larger than any we have in 
 North America, that of the Apurimac in Peru being in places 10,000 feet deep. The Huatacondo in 
 Chile, on the eastern border of the Desert of Atacama, is 3,000 feet deep, and the Calchaqui valley 
 at the eastern edge of the Puna de Atacama has almost the proportions of the Grand Canyon of the 
 Colorado but without its amazing architecture. The Andes contain also the highest peaks of the 
 western hemisphere: Aconcagua, 22,868 feet; Sajama, 21,385; and Mercedario, 21,877. Such 
 figures of peak heights are of no value whatever unless we know how frequently we encounter them 
 and at what elevation stands the platform from which they rise. 
 
 In view of this special character of the Andes a brief explanation of their land forms is given 
 at this point that the subsequent narrative and description of the Puna and its settlements may be 
 better understood. The coastal belt has already been described; the present concern is with the 
 interior chains and plateaus that form the Puna de Atacama, the southernmost unit of the Central 
 Andes. 
 
 After repeated crossings of the Andes in widely different latitudes I should say that it is not 
 their height and ruggedness that is their most surprising feature but rather the wide extent of high- 
 level plateau fragments and lava fields which form the platform upon which the highest peaks stand. 
 East of Iquique the sky line of the western summit of the Andes for at least forty miles is almost 
 unbroken. The top, seen from the west, is as even as if cut by a knife drawn along the edge of a 
 ruler. The elevation of the top averages about 12,000 to 14,000 feet. From this lofty platform the 
 snow-capped Cordillera Sillilica rises several thousand feet, but it is only in this small elevation that 
 the Andes are able to show a mountainous appearance. Their whole elevation above the sea has no 
 expression in the relief of today. In the Puna de Atacama the average height of the basin floors is 
 over 12,000 feet, and peaks and ridges rise to heights of only 1,000 to 5,000 feet about them. The 
 Salar de Uyuni, at the southern end of the great basin of western Bolivia, is 12,000 feet above sea 
 level, and there is little scope for the volcanoes on its border to make their distance above sea count 
 in the relief. 
 
 The volcanic features of the Central Andes were preceded in their development by a land 
 surface modeled to mature and even old forms over a vast extent of mountain country. There ensued 
 
 1 Isaiah Bowman, Desert Trails of Atacama , Am. Geogr. Soc., Special Publication No. 5, 1924, pp. 252-255 
 and map, p. 259. 
 
 2 J. J. von. Tschudi, Reise durcli die Andes von Siid-Amerika, Leipzig, 1866-1869. 
 
86 
 
 Earthquake Conditions in Ciitle 
 
 wide and great uplift in the late Tertiary and Pleistocene periods. The elevation of the whole sur¬ 
 face to higher levels was accompanied by the dissection of the mountain border as the draining 
 streams had their gradients increased; and on the floors of the valleys the most striking features are 
 the marks of recent and continuing dissection. Turbulent streams flowing over steep gradients dis¬ 
 lodge and transport great quantities of waste, which is strewn over all the basin and valley floors. 
 These marks of erosion at lower levels make more impressive the even crest lines of many plateau 
 masses and the open and parklike character of the landscape. Grassy swards abound, and gentle, 
 beautifully graded slopes. One’s imagination rather pictures the wilder mountain scenery of the 
 lower level culminating in bold peaks, whereas quite the contrary is the case. The top of the country 
 has in many cases the gentlest relief. Where even crest lines are lacking there is at least a succession 
 of graded mountain slopes showing late maturity of form. In other places all hut fragments of older 
 surfaces may be buried under lava flows. Neither the Coast Range of Chile nor the so-called Pre- 
 Cordillera along the eastern front of the Andes of northwestern Argentina is noted for its volcanic 
 material but rather for its sedimentary and intrusive material modeled on smooth lines. 
 
 Were these generalizations limited to a small area they might have correspondingly small sig¬ 
 nificance. On the contrary, they are characteristic of the whole Central Andes. More than that, the 
 studies that Willis has made in northern Patagonia and others have made in Peru, Ecuador, and 
 Colombia reveal in effect a similarity of topographic features throughout the whole Andean realm. 
 
 Willis 1 described the matureland of Patagonia as it occurs in the relatively low 
 and deeply dissected section of the Cordillera in the humid, strongly glaciated region. 
 On page 738 he says: 
 
 “ In ascending from the rivers or lakes of the southern Andes one encounters a change of 
 slope and passes from the steep canyon side into a gentler valley or on to a mountain spur at an eleva¬ 
 tion which varies from 1,200 to 1,600 meters above the sea. Standing at this level the observer recog¬ 
 nizes two distinct topographic phases. The one below him is that of the immature canyons. The 
 one above him is that of the mature valleys and divides of the region above the canyons. The latter 
 
 is the older.The characteristics of the mature topography of the upper zone are broad valleys, 
 
 sharp ridges, acute peaks and sometimes fairly extensive plateaus. 
 
 The matureland, having been recognized south of central Chile and also in 
 northern Chile immediately adjacent to the region under discussion, was looked for. 
 It was also realized at the beginning of the geographic study that the matureland is 
 a feature which by the very conditions of its origin must have antedated the uplift 
 of the Andes and should now be found at great altitudes as well as in the lowlands 
 of the coast ranges. 
 
 The matureland was found to be developed and preserved in the vicinity of Val¬ 
 paraiso, where it lies at an average elevation of about 650 feet (200 meters) above sea. 
 It is a flat upland, which supports hills and ridges of acute relief and is dissected by the 
 younger valleys of the Limache and Aconcagua. The rivers have cut down to grade- 
 level and are widening their valleys. The decay of the rocks to a notable depth is a 
 condition which marks the surface as one that has long been exposed to atmospheric 
 agencies while standing at an altitude so low that the streams could not carry off the 
 products of decay. It did not escape the acute observation of Darwin, who says: 
 
 “ It is worthy of remark that nowhere near Valparaiso above the height of twenty feet, or rarely 
 of fifty feet, I saw any lines of erosion on the solid rocks, or any beds of pebbles. This, I believe, may 
 be accounted for by the disintegrating tendency of most of the rocks in this neighborhood.” 
 
 In Darwin’s day, of course, the effects of secular decay of rocks had not been 
 emphasized by Pumpelly, nor had the criteria for the recognition of maturelands and 
 
 1 Bailey Willis, Physiography of the Cordillera de los Andes between the Latitudes of 39 and 44 South, 
 Compte Rendu, XII Congres Geologique, Toronto, 1912, pp. 733-756, with map. 
 
Events of Post-Cretaceous Time 
 
 87 
 
 peneplains been interpreted. Otherwise his logical reasoning would have found in 
 the disintegrated state of the rocks additional evidence in support of the proposition 
 that he maintained, namely, that the land had risen from a lower to a higher 
 elevation. 
 
 Going northward from Valparaiso, as did Darwin, I was interested to study 
 the features which he had examined nearly a century earlier. He had the advantage, 
 however, of going on horseback, whereas I went by train and could observe only at 
 distant points what he traversed slowly and continuously. North of Vallenar, how¬ 
 ever, I was privileged to penetrate the Cordillera on horseback and thus to enjoy 
 opportunities similar to those of Darwin’s time, and I had the advantage of his work 
 and of a hundred years of research. 
 
 Calera, the junction station 43 miles (69 km.) northeast of Valparaiso, at which 
 the northern longitudinal railroad leaves the Valparaiso-Santiago line, was the first 
 place which offered a convenient opportunity to examine the structure and physiog¬ 
 raphy of the outliers of the Andes. The town is situated in a valley which is from 
 1.5 to 3 miles wide and trends in a general way north and south along the contact 
 between the pre-Mesozoic diorite and metamorphic rocks which form the immediate 
 coast range and the bedded porphyrites of Jurassic age that constitute the higher 
 mountains on the east. 
 
 The origin of the Calera Valley may be attributed to either one of two condi¬ 
 tions. It may be a zone which has remained low while the ranges on either side of it 
 have been uplifted and is in that case homologous with the larger valleys of this type 
 farther north, as, for instance, between Vallenar and Toledo. On the other hand, 
 the Calera Valley may be regarded as a valley of erosion controlled in its course by 
 the zone of decayed granodiorite at the contact with the Jurassic porphyrite. It is 
 not impossible that both conditions have had a part in developing the valley, but I am 
 inclined to think that erosion has played a larger role than warping in this locality. 
 
 From Calera I took an afternoon ride into the mountains on the east, toward the 
 conspicuous mountain peak El Caquis (altitude 7,000 feet; 2,132 meters). I did not 
 reach the peak itself, since evening came on, but I ascended to a spur from which I 
 could overlook the broad upland upon which it stands. El Caquis is a sharply sculp¬ 
 tured monadnock rising boldly above a matureland. The reason for its survival as a 
 height is found in the fact that it lies at the northern end of a broad syncline which 
 pitches southward from it. The syncline is composed of the Jurassic porphyrites and 
 of sedimentary rocks, including the lower Cretaceous (Neocomian) limestones, which 
 are quarried for cement near Calera and Quillota. The peak appeared to be a rem¬ 
 nant of the limestones, but of that I can not be sure. 
 
 The matureland is to be seen as a narrow but well-developed upland, extending 
 over all the long spurs of the ranges at an altitude of about 4,500 feet (1,400 meters) 
 above sea. It is evidently the oldest topographic feature in the landscape of this imme¬ 
 diate region, and since it compares closely with similar maturelands observed through¬ 
 out north-central Chile, I regard it as probably of the same age. We shall hereafter 
 find reason to attribute to the Quaternary the great terraces which rest upon this ero- 
 
 10 
 
88 
 
 Earthquake Conditions in Chile 
 
 sion surface. It may therefore be regarded as having developed during the later Ter¬ 
 tiary, presumably from the late Miocene on into and through the Pliocene. 
 
 Opinions may differ as to whether the height on which El Caquis stands .should 
 be regarded as an inner part of the Coast range or as an outpost of the Andes them¬ 
 selves. I incline to the latter as the more correct statement of the relations, since the 
 divide between the water-sheds of the Aconcagua River on the south and the Rio 
 La Ligua on the north is continuous from east to west and descends from the summit 
 of Potrero Potrillo (13,000 feet; 3,965 meters) on the main crest of the Cordillera 
 to the sea, without interruption by any longitudinal valley. The matureland is con¬ 
 tinuous from the highest altitude to the coast itself, and the east-west courses of the 
 Aconcagua and La Ligua Rivers are consequent upon its westward slope. Their 
 valleys and those of their tributary streams appear to be attributable exclusively to 
 erosion and not to any local warping of the matureland. 
 
 The valley in which Santiago lies and which extends southward from a point 
 south of the Aconcagua River is so wide that it can only he interpreted as an area 
 which has remained relatively low, while the ranges east and west of it have been 
 uplifted, producing both warped and faulted surfaces. But that depression termi¬ 
 nates a short distance north of Santiago, no doubt for good structural reasons. It is 
 possible that the great fault which bounds the valley of Santiago on the west trends 
 northeast up the Putaendo Valley and continues northward in the region of the head¬ 
 waters of the Rio Colorado, a branch of the Calindasta, which flows to the Atlantic. 
 I was unable, however, to test this inference, which rests upon a study of the maps 
 and the possible continuation southward of the fault systems observed north of 
 La Serena. In any case, the western slope of the Andes in the vicinity of latitude 32 0 
 may be regarded as continuous from the crest to the sea, and as scored simply by the 
 canyons of the consequent streams which have grown upon it and have sunk deeply 
 into it during the process of uplift. 
 
 At Combarbala the railroad reaches an altitude of 3,000 feet (900 meters). The 
 immediately surrounding landscape seen from the station is a hilly upland, the gentle 
 profiles of which may be followed up into the heights of the Andes toward the east 
 and also to the north and south. The deep canyon of the Rio de Combarbala, in which 
 the city itself lies, is easily overlooked in the view northeastward, and the still deeper 
 canyon of the Rio Guatulame on the west is not in sight. Both of these are much 
 younger gorges as compared with the matureland which is obviously a continuation 
 of that seen near El Caquis and in the heights of the Cordillera. 
 
 Combarbala is in latitude 31 0 11' S. Thence northward the railroad descends to 
 Ovalle, on the Rio Limari, and then winds northward through the coast range to 
 Coquimbo Bay. Following it, I did not again see the heights of the Cordillera until 
 in the vicinity of latitude 28°. But the matureland is recognizable in the coast range 
 and in the foothills of the Andes, and is without doubt continuous as a feature of 
 greater altitudes throughout the stretch of 210 miles (336 km.) between the areas at 
 which it was observed. It was found again in latitude 28°, on the headwaters of the 
 Rio Manfias. 
 
Events of Post-Cretaceous Time 
 
 89 
 
 Having followed up the Copiapo River to the point where it receives the Manfias 
 from the south, I ascended into the mountains between the Manfias and the Montosa 
 and proceeded south to the upper Manfias, the detour being necessary in order to 
 avoid the impassable canyon of the lower section of the Manfias. The divide between 
 the Manfias and the Montosa lies close to the latter and is formed by a high range 
 carrying the peaks of Cerro de la Iglesia (12,600 feet; 3,840 meters), Cerro Crespo 
 (13,600 feet; 4,150 meters), Cerro Berraca (14,660 feet; 4,470 meters), and Cerro 
 del Toro, of the same altitude as the last named. This ridge has a length of about 
 25 miles (40 km.) and rises boldly probably 3,000 feet (1,000 meters) above a group 
 of upland valleys. Its abrupt face is probably a deeply eroded fault scarp. The ele¬ 
 vated valleys are distinguishable by their deep soil and gentle grades from the rock- 
 walled canyons that are sunk far below them. I regard their area as representative of 
 the matureland seen elsewhere, both north and south. Its topographic aspects are re¬ 
 peated on the headwaters of the Manfias, where Cerro Pircas Blancas and Cerro Can- 
 taritos, rising to approximately 18,000 feet (5,500 meters), overlook extensive up¬ 
 lands of gentle relief. The same features are continued in the upper valley of the Rio 
 Laguna Grande and its immediate tributaries. The occurrence of extraordinarily 
 thick and heavy gravel deposits which form cliffs above Laguna Grande indicates that 
 the valley in which that little lake occurs is probably of post-Pliocene date, since the 
 gravels themselves may be assigned to that period or to the early Quaternary. But 
 Laguna Grande itself lies in a canyon about 3,000 feet (900 meters) below the level 
 of the passes which represent the matureland. 
 
 A little farther north, in latitude 27 0 50', and some 30 miles (48 km.) west of the 
 last-described region, is the Chanarcillo mining district, which is well known for its 
 very large production of silver. The altitudes in that vicinity range from about 2,500 
 to 3,000 feet (750 to 850 meters), but there is, nevertheless, the same type of mature 
 topography to be seen in these hills and valleys as in the heights of the Andes. The 
 type is one of mature relief, with broad, aggraded valleys and deep soil, except where 
 the wind has carried it away. At Chanarcillo, moreover, we have the evidence of 
 prolonged activity of the atmospheric agents in the enormous amount of secondary 
 enrichment of the mineral deposits. It is to the widespread occurrence of the mature- 
 land that Chile owes the great concentration of silver ores which have yielded so much 
 wealth. 
 
 In going north from Copiapo, the longitudinal railway turns first to the south¬ 
 east to Paipote and then winds up a long, steep grade to the pass of Chimbero, where 
 it reaches an altitude of 6,500 feet (1,978 meters). The lower part of the ascent is 
 up the aggraded younger valleys of Quaternary age, but after passing Carrera Pinto 
 one is again in the upland which represents the matureland and on which is situated 
 the well-known Dulcinea mine and many others. From Chimbero the matureland 
 descends toward the depression that lies to the north and east of Pueblo Hundido 
 beyond the Ouebrada del Rio Salado. 1 his is the first of the wide basins in which 
 the nitrates occur. 
 
90 
 
 Earthquake Conditions in Chile 
 
 The physiographic unity of the western slope of the Andes is well exhibited in 
 the ascent from Pueblo Hundido eastward to the great copper-mining camp of 
 Potrerillos. The distance in a straight line is about 50 miles (80 km.) and the differ¬ 
 ence of elevation is about 8,000 feet (2,400 meters), Pueblo Hundido being 2,500 
 feet above sea and Potrerillos camp 10,400 feet. The ascent is made up the canyon 
 of the Rio Salado and then by a winding grade along the canyon wall to the mining 
 camp, which is situated on a gravel plateau at 10,400 feet (3,100 meters). From 
 the camp the eye may sweep the entire western slope and may follow the long grade 
 of an old early Quaternary or Pliocene river terrace down the unbroken incline to 
 the basin at Pueblo Hundido. Behind one toward the east the hills and valleys rise 
 somewhat more steeply to the old valley levels at 12,000 to 14,000 feet (3,600 to 4,200 
 meters), which represent the old surface of mature topographic erosion that we have 
 traced from above Valparaiso and the vicinity of El Caquis. (See Plate XLVI.) 
 
 When one rides north and east from Potrerillos to the Salar de Pedernales and 
 thence north to the Salar de los Infieles one is on the high plateau of the Andes among 
 peaks that reach 18,000 to 20,000 feet (5,400 to 6,000 meters). The old erosion sur¬ 
 face persists at altitudes of 14,000 to 16,500 feet (4,200 to 5,000 meters) in the form 
 of wide valleys separated by low maturely eroded divides. It is, however, displaced 
 along fault-lines and is to a considerable extent buried beneath the debris from vol¬ 
 canic peaks that stand along the faults. Since the volcanic activity goes far back into 
 the Tertiary and comes down to the present there is every possible relation of age 
 between the different volcanic formations on the one hand and the matureland on the 
 other. But the latter is nevertheless recognizable as an extensive feature of the high 
 Cordillera. (See Plates XLIII, XLIV.) 
 
 From Potrerillos I returned to the longitudinal railway at Pueblo Hundido (lat. 
 26° 23') and thence went north by rail to Calama and the great copper mine of Chu- 
 quicamata (lat. 22 0 25'). The railroad skirts or crosses the nitrate basins, wide, flat 
 surfaces of gravel and soil impregnated with nitrate of soda, from which rise the 
 characteristic hills and peninsulas of a buried topography which, in its profiles, is iden¬ 
 tical with that of the landscape of the coast range itself and of the high Andes. 
 Everywhere are the signs of the mature phase of erosion. The nitrate basins lie at 
 elevations of 3,000 to 7,000 feet above sea (1,000 to 2,500 meters), with a somewhat 
 higher coast range between them and the ocean and the very much higher basins and 
 summits of the Andes east of them. The nitrate basins now lie at an elevation such 
 that rivers flowing from them, if there were any, would cut deep canyons and the 
 process of erosion would be destructive of their present form and also of the mature 
 forms that are buried beneath the debris with which they are deeply filled. It is obvi¬ 
 ous that the sculptured mature surface now stands high above its original position; 
 that is, it has been elevated, not depressed, with reference to sea-level. Nevertheless, 
 we constantly refer to these basins as depressions because they lie at a lower altitude 
 than that of the more vigorously uplifted mountain ranges which border them. 
 Although they have shared in that upwarping of a wide zone of the earth’s crust 
 which has formed the Andes, relatively to the mountain ranges they are downwarped. 
 
Events of Post-Cretaceous Time 
 
 91 
 
 The railroad journey afforded no opportunity for specific local observation, but 
 on arriving at Chuquicamata I was able to make extended excursions in the valley 
 of the Rio Loa and the adjacent mountain region. The country exhibits the same 
 characters of mature erosion marking the landscape of the oldest surface to be seen, 
 and I concluded that the earliest phase of physiographic history which could be iden¬ 
 tified in the coast ranges, in the Cordillera, and in the basins and valleys between them 
 was one and the same from Valparaiso to Calama, a distance of about 750 miles 
 (1,200 km.) from north to south. 
 
 EPOCH OF CANYON DEVELOPMENT 
 
 The cordilleran matureland which has thus been identified by Bowman and my¬ 
 self as a characteristic feature of Andean physiography, from latitude 44 0 in Pata¬ 
 gonia to latitude 18 0 in southern Peru, belongs to a long topographic cycle which 
 began with the elevation of the Andes above the Neocomian sea-level. That early 
 uplift and the minor steps by which the land reached its greatest elevation of that 
 time, at the close of the Mesozoic or during the Eocene, are not recorded. They were 
 lost as the matureland developed and it remains as the oldest general feature of the 
 Cordillera. 
 
 The matureland is now found underlying the nitrate basins and other wide 
 depressions of the Coast ranges and is also identified in the salt plains of the high 
 Cordillera, as well as in their surrounding divides. It can be traced from the lowest 
 to the higher elevations as an erosional surface, which is now entirely out of harmony 
 with its environment; that is to say, it not only could not have developed in the alti¬ 
 tudes and at the elevations where it still exists, but is either being buried or dissected 
 by the activities of aggradation or corrasion. A great change has occurred in the 
 zone of the Cordillera since the age when the matureland extended its hilly and 
 somewhat monotonous landscape over the Pacific coast of South America, and that 
 change is nothing less than the elevation of the Cordillera itself. 
 
 The elevation of the matureland resulted in the corrasion of canyons, typical 
 of the youthful phase of topography thus initiated. There was, of course, a drainage 
 system already established on the matureland. It had become adjusted to the struc¬ 
 tural trends of the land, except in so far as it had been disturbed and diverted by the 
 concurrent volcanic activity, which was both widespread and persistent, as is shown 
 by the Tertiary eruptives. But the adjusted drainage must have had predominantly 
 north-south trending valleys in the matureland, connecting with the sea by short 
 transverse courses. Thus the early Tertiary stream-pattern was of the grape-vine 
 type, somewhat like that of the Appalachians, but less regular in general plan and 
 locally very irregular. 
 
 The growth of the canyon system modified the older, adjusted drainage by 
 extending the water-sheds of the transverse courses and by capturing the adjusted 
 valleys in favor of the vigorous master-streams. The predominant effect was to pro¬ 
 duce such rivers as the Limari, the Elqui, the Huasco, the Copiapo, and the Salado, 
 which flow from the junctions of their main tributaries in rather direct and simple 
 
92 
 
 Earthquake Conditions in Chile 
 
 courses to the ocean. They are to a considerable extent consequent on the western 
 slope of the Cordillera and independent of structural control. 
 
 The headwaters of these streams show remnants of the older system and exhibit 
 signs of capture. Thus the Rio Hurtado, a branch of the Limari, makes a right-angle 
 bend just south of the Portillo de Tres Cruces (30° 20' south latitude), through which 
 it once flowed to the Elqui. The stronger Limari here captured the tributary of the 
 Elqui, which is represented by its beheaded lower course, the Ouebrada Pangue. 
 
 A similar capture is found on the Rio Elqui (just north of latitude 30°), where 
 both the Rio Claro and the Turbio change their courses sharply from northwest to 
 west and southwest. They may formerly have run to the truncated Rio Choros. 
 
 The captures thus effected by the Limari and the Elqui are such as would occur 
 if the captured headwater tributaries had been slowed up by faulting while at the 
 same time the grades of the southwest-flowing streams had been increased by the 
 elevation of the Cordillera de la Punilla on the north. It will be observed that there 
 are two thrust-faults which we saw at Rivadavia and Paiguano and which define the 
 zone of capture in such a way as to sustain this suggestion. 
 
 The headwaters of the Rio Huasco, comprising the Carmen and Transito, do 
 not betray their former courses to simple inspection, if indeed they have undergone 
 material change. At the point where the Transito turns west (near latitude 29 0 ), 
 the wide valley is appropriately called La Pampa, and a very narrow gorge just west 
 of La Pampa is known as El Portillo. These local features are probably due to the 
 fault that crosses the valley just west of El Portillo, but the plan of the stream is, 
 nevertheless, that which may reasonably be credited to the old adjusted, grape-vine 
 system. 
 
 The Copiapo River gathers its waters with both hands, so to say, at a point 
 within the zone of faulting in the high Cordillera. The Jorquera and Pulido from the 
 north and the Manfias and Montoso from the south meet in pairs after the fashion 
 of grape-vine drainage. Their united waters, however, take a peculiar northwest 
 course, in lieu of flowing west by the shortest route to the sea. It is possible that they 
 formerly did run west across that now arid basin whose center is by contrast with its 
 general sterility called Yerba Buena (latitude 28° 5'), and were diverted northward 
 and westward at an early stage of the general uplift and accompanying faulting. The 
 basin alluded to is characterized by the features of the matureland and by deep oxi¬ 
 dation of the ores, as at Chanarcillo. It is an area which has not undergone any con¬ 
 siderable erosion since the early or middle Tertiary. In these and other stream sys¬ 
 tems interesting problems are presented. They require careful study of the topogra¬ 
 phy and structural geology. They also have a bearing on the distribution of valuable 
 mineral deposits, since the latter are most likely to be found where the matureland 
 survives unchanged. 
 
 The object of this description and suggestion is to call attention to the epoch of 
 canyon development which ensued upon the beginning of the uplift of the Cordillera. 
 It is an occurrence which must necessarily be recognized as one of the phases of the 
 topographic cycle that is recorded in the features of any mountain range. It dates 
 
Events of Post-Cretaceous Time 
 
 93 
 
 from the beginning' of the uplift and it can not be said to have come to an end until 
 the topography passes into the phase of early maturity. That is very far from being 
 the case in the Andes. The mountain chain is still very young; nevertheless, there are 
 episodes which are superimposed upon the record of canyon development and which 
 demand consideration here, because they bear directly upon the earthquake problem 
 in its relation to the structure of the mountains. I refer to the gravel deposits that 
 now fill the valleys and canyons and which by the continuity of their surfaces demon¬ 
 strate that active faulting long ago ceased to be expressed at the surface, even where 
 earthquake shocks are violent. 
 
 The epoch of canyon development probably dates from the middle Tertiary and 
 extends down to and beyond the Present. The reason for assigning the date of begin¬ 
 ning of the epoch is found in the occurrence of Pliocene deposits along the present 
 coast in positions that had been shaped by the uplift and erosion before that period. 
 The Miocene, on the other hand, appears in very slight develoment, if at all, as 
 marine sediment. The single fossil from Coquimbo is the only local evidence, and it 
 is found in a faulted stratum in such relation as to indicate that it had been disturbed 
 before the Pliocene. We shall therefore not be far from the truth if we assign the 
 uplift and faulting of the coast range in this section to the late Miocene and Pliocene. 
 This is the early part of the stage of canyon development, corresponding with the 
 excavation of the river gorges as they now exist. But they have since been partially 
 filled with gravel deposits of unusual character. 
 
 GRAVEL DEPOSITS 
 
 The river valleys of the coast range and of the Cordillera to its highest plateaus 
 are filled with voluminous deposits of sands, gravels, and cobbles, which are so omni¬ 
 present that they form one of the most impressive features of the geologic record. 
 They are paralleled in other lands under different conditions. For instance, the ter¬ 
 races along the Columbia River in British Columbia and the northwestern United 
 States are similar in magnitude to those along the Huasco between Vallenar and the 
 sea. The terraces of the Loess district of China are equally striking. The desert 
 plains of Nevada stretch across deposits of the same order of magnitude, but not yet 
 terraced because the basins are still inclosed. Thus the accumulations of fluviatile 
 sediments are found where rivers, glaciers, or winds have worked. The three agents 
 have always worked together, but sometimes one, sometimes another, has been pre¬ 
 dominant. The texture, internal structure, or environment serve to distinguish the 
 different types of deposits, but they have in common the character of great volume 
 and wide distribution. 
 
 The condition precedent to the accumulation of voluminous deposits of this 
 character was the deep decay of the rocks during a prolonged period of relatively 
 humid climate and comparatively low level. Pumpelly first observed and described 
 this essential prerequisite. 1 It is so directly essential to the gathering of great alluvial 
 
 1 R. Pumpelly, The Relation of Secular Rock-disintegration to Loess, Glacial Drift, and Rock-basins, Am. 
 Jour. Sci. (3), 17, pp. I 33 -M 4 , 1879. 
 
94 
 
 Earthquake Conditions in Chile 
 
 deposits that one may fairly assume the previous existence of a matureland or pene¬ 
 plain in any now mountainous province in which they are found. This inference 
 is fully justified in Chile, as has been described. 
 
 Darwin was very much impressed by the gravel formations of the Patagonian 
 plateaus and of the Cordillera in central Chile. He described them in his Geological 
 Observations with his usual keenness and accuracy. 1 It is to be regretted that the 
 state of geologic opinion and theory in his early days leaned unduly toward the idea 
 of marine erosion, and he attributed the extensive river deposits to the action of 
 marine currents. Ingenious as is his reasoning in defense of the adopted hypothesis, 
 one can not help wondering whether it was wholly satisfactory to his logical mind. 
 It appears that he was influenced by observing at Coquimbo and La Serena the inti¬ 
 mate association of marine and fluviatile continental formations, where the deposits 
 naturally meet, just as the river naturally flows into the ocean. 
 
 The gravel deposits are now recognized as an effect of river action, it being 
 established that climatic changes have occurred and that the arguments which pre¬ 
 vailed with Darwin are not valid. While it is true, as he stated, that the rivers are 
 incapable of forming the terraces under present conditions, it is beyond question that 
 they have in the past had the appropriate volume to carry and the moderate fall on 
 which to deposit the detritus. We recognize the agent. It remains to distinguish the 
 combinations of conditions which enabled it to do the work. Climatic changes consti¬ 
 tute one important group, modifications of slope another. 
 
 My own observations accord entirely with Darwin’s. On the Rivers Elqui, 
 Huasco and Copiapo the canyons in the western slope of the Andes are fringed with 
 narrow terraces, as he has described them. The depressions that lie between the Cor¬ 
 dillera and the Coast range are floored by the gravels, and the valleys by which the 
 streams flow through the Coast range to the sea are also deeply filled and in part 
 reexcavated, forming terraces. 
 
 A somewhat different condition exists on the Rio Salado, in latitude 26° 30'. 
 The canyon through the Coast range is not conspicuously terraced, although its valley 
 is a gravel plain. At Pueblo Hundido, where the depression at the foot of the Andes 
 forms a desert basin at an elevation of 2,600 feet (800 meters) above sea, there be¬ 
 gins a long slope which rises to Potrerillos at 10,400 feet (3,100 meters). It is a 
 gravel slope, which fringes the canyon of the Rio Salado and all of its tributaries, 
 covering the rocks deeply, except where occasional pinnacles protrude through the 
 mantling deposit. The gravels are thus continuous from a comparatively low altitude 
 to the heights where the salt plateaus and volcanic peaks form the summit of the Cor¬ 
 dillera. They furthermore extend not only along the canyons between the precipitous 
 walls, as on the upper stretches of the other rivers named, but also over the inter¬ 
 stream areas of the old matureland. 
 
 The contrast between conditions on the Rio Salado and the rivers farther south 
 serves to emphasize the fact that the terrace deposits occupy two very different posi- 
 
 1 Charles Darwin, Geological Observations in South America, first edition, London, Smith, Elder & Co., 
 1846, pp. 62-67. 
 
Events of Post-Cretaceous Time 
 
 95 
 
 tions, even where the upper surfaces are confluent. This is but one suggestion of the 
 complexity of their constitution and of the diversity of age to be found among them. 
 Thus on the Elqui, Huasco, and Copiapo the gravels which fringe the canyons were 
 deposited necessarily after the canyons had been eroded, at the close of the period 
 of canyon development. This was long after the beginning of the uplift to which the 
 canyons are due. On the other hand, where the gravels cover the floors of the exten¬ 
 sive depressions, burying the matureland as they do in all of the longitudinal valleys, 
 they must have begun to accumulate as the basins were formed, that is during the 
 process of uplifting. Thus the lower formations in the basins are materially older 
 than the terraces in the canyons. 
 
 It is desirable to distinguish these two groups of terrace deposits or gravel for¬ 
 mations, and to do so I shall refer to the older, which covers the matureland, as the 
 mantling gravels or formation, and to the younger, which occurs along the canyons, 
 as the fringing deposit or formation. 
 
 It might, perhaps, be suggested that a geographic term should be used as a name 
 to designate each of these formations, but it does not appear appropriate to do so in 
 this report because of the brief and generalized character of the description, which 
 is all that my observations justify. The terms “ mantling ” and “ fringing ” are here 
 used, not as names, but as descriptive adjectives, which may serve adequately to dis¬ 
 tinguish the gravels of the basins from those of the river valleys. 
 
 The mantling gravels were first recognized in the longitudinal valleys. They 
 cover the matureland. A typical occurrence may be studied in the wide downwarp, 
 in which Vallenar is the principal pueblo, and in the valley of the Huasco, where it is 
 cut 200 meters deep in the deposits. 
 
 The downwarp extends 125 miles (300 km.) from north to south and is about 
 5 to 12 miles (8 to 20 km.) wide. The actual surface is a broad gravel plain, which is 
 locally scored by shallow ravines. Around the margins of the plain the latest of the 
 mantling gravels merges into alluvial cones of relatively recent deposition or rests 
 upon the decayed rocks of the matureland. It is thus a transgressive deposit, which 
 overlaps upon the old landscape surface. In some cases the old gravels abut against 
 freshly exposed rocks, as if along a fault scarp, but that is exceptional. Thus it ap¬ 
 pears that the deformation by which the downwarp was formed was accomplished by 
 flexure, rather than by fracture, at least in the later stages. The transgression upon 
 the matureland is well shown around the basin of the Rio Totoral, west of the rich 
 mines of Chanarcillo. 
 
 If we assemble into a moving picture the sequence of events connected with the 
 deposition of the mantling gravels, we first review the aspects of the matureland in 
 its last stage of erosion under the normal conditions of a humid climate, favorable to 
 rock decay and soil accumulation. Warping ensues. The area of the downwarp 
 becomes a basin, which, even though it be raised as it is warped, is nevertheless 
 aggraded by the loaded streams that flow from the adjacent upwarps. Alluvial fans 
 grow, coalesce and form a plain. Humid and arid climates, warm or cold may alter- 
 
96 
 
 Earthquake Conditions in Chile 
 
 nate; any phase of the activities of rivers, lakes, cloudbursts, or even of distant gla¬ 
 ciation may be represented in the basin deposits. 
 
 The latest of the mantling gravels are naturally sought in the highest terrace- 
 levels around the basins. They are very well preserved along the Copiapo River in 
 the southern part of the basin in which the city is built. The gravels consist of coarse 
 fluviatile material from which the sand has been blown away, leaving a surface of 
 large pebbles and cobbles. The stones are largely of Mesozoic porphyries, quite dark 
 in color but also darkened by desert varnish. They are very commonly pitted by wind 
 erosion, a typical characteristic that is significant of their age and is wanting on the 
 lower, younger terraces. (See Plate XLVII.) 
 
 Within this oldest terrace of the Copiapo Basin there are relatively recent river 
 deposits consisting of sands that are remarkably well jointed, as illustrated in Plate 
 XLVII I A. They belong to a much later activity than the deposition of the mantling 
 gravels and may be related to some recent phase of the fringing gravels. 
 
 The continuity of the highest and oldest terrace of the mantling gravels around 
 the basin of Copiapo is a striking fact. About a mile and a half (2 km.) southwest of 
 the city a long, low ridge of rock rises from the river plain to a height of 30 feet (10 
 meters) above it, and the slope is carried hack westward to the hills by an old alluvial 
 fan. Where the latter is cut away by erosion younger fans have developed at a lower 
 level. The rock ridge and the old fan belong to the epoch of the highest terrace and can 
 be followed around the western and southern sides of the valley to the Ouebrada de 
 Paipote. Along the eastern side erosion has cut more deeply into the old terrace. It is, 
 however, nowhere dislocated by faulting. The age of the highest terrace deposits in 
 this vicinity is indicated by the pitted, wind-eroded pebbles. (Plates XLVII, 
 XLVIII.) They reach far back into the middle or possibly early Pleistocene. What¬ 
 ever their age, they are younger than the latest notable displacement by faulting in 
 the Copiapo Basin. This conclusion banished the expectation of finding recent earth¬ 
 quake rifts by which to explain the severity of the shock of 1922, or of others which 
 have given Copiapo the distinction of being an earthquake center. 
 
 The mantling gravels exhibit a very interesting distribution. In the vicinity of 
 Coquimbo they are confined to the valleys immediately adjacent to the seacoast, if, 
 indeed, they are present as gravel deposits, or they are represented by the Pliocene 
 marine formations of Coquimbo Bay. Farther north, about Vallenar, the mantling 
 gravels have their typical development in the longitudinal valley, both north and 
 south of the Huasco. Still farther north they fill the basin in the vicinity of Pueblo 
 Hundido, but extend thence eastward up the slope of the Andes to an altitude of more 
 than 10,000 feet (3,000 meters), filling the ancient valley of the Rio Salado and its 
 tributaries. The terraces along the Salado extend for 50 miles (75 km.), from near 
 Pueblo Hundido to Potrerillos, without a break, but their present inclination is such 
 that the river has cut a canyon 1,600 feet (500 meters) deep through the gravels into 
 the underlying bedrock. 
 
Events of Post-Cretaceous Time 
 
 97 
 
 In the section on the Rio Salado the gravels are thick in the lower basin, but com¬ 
 paratively thin higher up on the slope. They thus appear to represent the accumula¬ 
 tions in the downwarp in the one case and in the ancient river valley in the other. 
 
 The distribution and thickness of the mantling gravels thus affords in general 
 a means of tracing out the ancient topography on which they were first laid down 
 and the subsequent changes of level that have favored their deeper accumulation in 
 the basins. Should they ever yield vertebrate or other fossils, as is not improbable, 
 they will furnish the data for dating the beginning of the actual uplift of the Coast 
 Range. 
 
 The fringing gravels are those which occur in the river canyons, along both 
 sides of the rivers, as described by Darwin. They are evidently younger than the 
 canyons in which they lie, whereas the mantling gravels are probably to a large extent 
 formed of the material eroded from the canyons and consequently of similar age. 
 
 The fringing gravels are well developed along the Rio Elqui, the Huasco, and the 
 upper Copiapo. They are typical river deposits, derived to a great extent from side 
 canyons and often consisting of nothing more than the alluvial fan of a tributary. 
 They do not appear to represent anything more than the transient aggradation of 
 the river’s course and subsequent partial erosion, in consequence of climatic changes, 
 under favorable conditions of high elevation. Nevertheless, these gravels are not 
 recent. The terraces which they constitute are usually high above the streams, beyond 
 the reach of the highest floods, and the rivers run in rock gorges in many long 
 stretches. The character of the gravels and the depth to which the rivers have cut 
 since they were deposited indicate a lapse of time coordinate with that which can 
 elsewhere be correlated with the epochs since the retreat of the older glaciation from 
 the Pacific ranges of the United States and British Columbia. 
 
 The Rio Huasco presents a peculiarly interesting opportunity to study the mant¬ 
 ling and fringing gravels. At Vallenar it exposes the deepest section in the former. 
 East of the longitudinal valley it is fringed with characteristic occurrences of the 
 latter; and above Laguna Grande, on its head waters, at an altitude that lies between 
 13,000 and 15,000 feet (4,000 and 4,500 meters) there are high cliffs of a gravel for¬ 
 mation, which by its great thickness and very coarse character challenges investiga¬ 
 tion. It presents the appearance shown in Plate XLIX B, as one looks up from the 
 outlet of Laguna Grande. The lake itself is formed by the blocking of the valley by a 
 large slide from the cliffs. The environment of the deposit could not be observed from 
 below. The best guess as to its correlation and origin which the available data permit 
 is that it is a remnant of the mantling gravels carried up in the elevation of the block 
 east of the fault that runs through the valley of Laguna Grande and past the peaks 
 of Las Cantaritas and La Iglesia. 
 
 As regards the age of the gravels, it will be apparent from what precedes that 
 there is reason to assign the oldest beds of the mantling gravels to the early Pliocene 
 or earlier and the fringing gravels to the Pleistocene. If we include with the latter 
 the recent and actual alluvial fans, the record is continuous down to the present. We 
 
98 
 
 Earthquake Conditions in Chile 
 
 thus introduce, however, the episode of river erosion by which the streams have 
 re-excavated their channels in the gravel formations. It is well to do so, since the 
 earlier history probably comprised similar changes in the activity of the rivers, which 
 at times aggraded and at other times eroded their beds. 
 
 The purpose of this chapter is accomplished if it has succeeded in suggesting 
 the complexity of the record that lies concealed in the gravel deposits of central Chile. 
 They appear to cover all late Tertiary, Pleistocene, and Present time. They have 
 accumulated under all the different conditions of climate which have passed over 
 the region during the later geologic ages. The oldest beds, although younger than 
 the middle Tertiary faulting, date from the beginning of the Cordilleran uplift. 
 The latest gravels were washed down in the last storm. The intimate study of the 
 formations will eventually decipher a sequence of events even more complex than 
 that of the glaciation of northern Europe and North America, for diastrophism is 
 associated with climatic change as a cause of variation in the nature of the deposits. 
 
 Since the gravel deposits include those of Pleistocene age, the observer will look 
 for evidences of glaciation and will find traces of them. But they are far from com¬ 
 mon and it is desirable to describe in some detail those which we happened to observe. 
 
 EVIDENCES OF GLACIATION 
 
 Central Chile is not a region in which one would expect to find evidences of gla¬ 
 ciation on any large scale. Of the conditions that favor the accumulation of neve 
 and glacial ice—humidity, high latitude, and high altitude—only the last named is 
 present, and it is obvious that the great altitudes of the Cordillera were requisite to 
 produce glaciers, in view of the aridity of the atmosphere and the relatively low lati¬ 
 tude of 30° more or less. It is therefore in the heights of the Andes that we should 
 look. 
 
 This deduction bears also upon the age of the uplift of the range in relation to the 
 glaciation. The Cordillera must have had nearly, if not quite, its present elevation 
 when glaciers developed. Either the uplift had attained its present condition before 
 the Pleistocene or if the Andes were materially lower than now at the beginning of 
 that period, the glaciation belongs to the later Pleistocene. 
 
 Certain evidences of glaciation were found near Potrerillos, in latitude 26° 30', 
 at an elevation of 11,000 feet (3,300 meters). The railroad which ascends from the 
 camp to the mine winds about a spur of the mountain at about a mile and a half 
 (2 km.) from the former, and runs along a steep slope into a ravine. The exposure is 
 toward the southwest, and in this southern latitude corresponds to the cold northwest 
 exposure of the northern hemisphere. Plere, if anywhere, snow would linger and 
 accumulate. 
 
 In excavating the grade the superficial talus was removed and a firm surface 
 of gravel was uncovered. It was fortunately not disturbed and in May 1923 showed 
 all the details of grooving and striation which are illustrated in Plates L and LI. They 
 appear to be the markings characteristic of the sole of a glacier. 
 
Events of Post-Cretaceous Time 
 
 99 
 
 The parallel grooves in the gravel and the striations on the pebbles slope down 
 the ravine in the direction which would have been followed by a mass of ice that filled 
 the ravine and ground against its side. The head of the ravine has not the cirque-like 
 form that would suggest glacial plucking, but is sufficiently inclosed by mountain 
 slopes that rise to 13,000 feet (4,000 meters) or more in altitude to afford a shaded 
 basin in which the neve could have gathered. 
 
 The alternative explanation that the gravels had been caught in a fault and 
 striated by friction on the fault plane was excluded by the character of the gravel 
 formation itself and by the impossibility of reconstructing an overlying rock-mass 
 that could have done the work. 
 
 The evidence appears to show conclusively that there was a Potrerillos glacier- 
 ette, which had mass enough to consolidate and striate its bed, but did not linger long- 
 enough to sculpture its valley to any perceptible degree. It was not over a mile and 
 a half (2 km.) long above the exposure and probably did not extend far down the very 
 steep gorge below; but small though it was, it has left an indubitable record of glacial 
 conditions in this latitude and at this altitude. 
 
 The age of the glacierette appeared a matter of much interest. In the bed was 
 a quartz boulder of a deep red color, which when dug out was found to be creamy 
 white. The red coloration was due to oxidation, which had affected the soled surface 
 left by the glacier and had penetrated about half an inch into the cobble. Since the 
 color was red, not yellow, there had been but little hydration, and the effect was chiefly 
 that of the dry air under the talus. There were no granite boulders with which to 
 compare, but the oxidation appeared to represent an effect comparable with that of 
 the decay of granite boulders in the drift of the United States and thus suggests that 
 the Potrerillos glacierette was an early Pleistocene incident. 
 
 A comparison with Patagonian glaciation also suggests that the cold episode in 
 this northern latitude probably corresponded with the earlier of the two glaciations 
 that have there been recognized, rather than with the later; for the large glaciers 
 that gathered in the Andes in latitude 41 0 south have left very distinct moraines, and 
 the older ones lie many kilometers further down the valleys. The earlier glaciation 
 was therefore the more severe and would be the one that would leave traces, if any 
 were left, in the drier, warmer zones. 
 
 In one other instance we ran across distinct evidences of glaciation, but not in 
 place. In the Quebrada del Hielo (an appropriate name) Dr. Felsch and I found a 
 small group of boulders of limestone lying as erratics upon a Tertiary volcanic tuff 
 in the flat floor of the valley. (Plate LII B.) They were distinctly out of place. 
 Nothing in the underlying rocks resembled them. They were rounded, surfaced, and 
 striated, and, being from 5 to 6 feet (1.5 to 2 meters) in diameter, were such masses as 
 to be beyond the carrying power of the small stream, unless in time of cloudburst or 
 floating ice. They may have been transported by the former agency, which is by no 
 means rare in these arid ranges, but the striations and planed surfaces can not be 
 attributed to anything except glacial grinding. 
 
100 
 
 Earthquake Conditions in Chile 
 
 The point where these boulders lie is west of a range which reaches altitudes of 
 15,000 to 16,500 feet (4,500 to 5,000 meters), being dominated by Cerro Azufre, a 
 volcanic peak which rises to 16,760 feet (5,080 meters) above sea. The latitude is 
 27 0 10', and therefore slightly more favorable than that of Potrerillos. It would thus 
 appear that the boulders are evidence of glaciation in the heights of this portion of 
 the Cordillera, at least to the extent of a glacierette or two. 
 
 These facts had already established glaciation as one of the conditions of which 
 I took account when I began the study of the Plio-Pleistocene section at Coquimbo. 
 It nevertheless was with surprise and doubt that I observed the large boulders which 
 occur in the marine section there and which seem to indicate that the coast also was so 
 refrigerated that ice formed locally in a deep ravine in such quantity as to be compe¬ 
 tent to float them. The facts are stated in the description of the Coquimbo formation. 
 
GEOLOGY ON COQUIMBO BAY 
 GENERAL STATEMENT 
 
 Coquimbo Bay occupies a structural depression and is doored with Pliocene and 
 Pleistocene sediments which also form terraces around its shores. It thus epitomizes 
 the later history of the Chilean coast. During the later Tertiary, possibly as early 
 as the Miocene, its basement of Paleozoic granite was faulted, a ridge was elevated 
 along its western margin, and a wide area east of the uplift was depressed. The 
 depression reached its lowest level during the Pleistocene, probably during a mid- 
 Pleistocene, interglacial stage, and the entire district has since been raised, including 
 the granite ridge on the west. The story may be read in the structure of the rocks, 
 the physiography of the hills, the fluviatile and marine terraces, the ice-transported 
 boulders, the fossils and the marine life now inhabiting the bay. It is a consistent 
 story, which can be sketched in outline from the observations of Charles Darwin and 
 his successors, but which still offers a rich opportunity for investigation to the stu¬ 
 dent who may have time to work out its details and the training required in various 
 branches of geology and paleontology. 
 
 The accompanying chart (Plate LV) shows that Coquimbo Bay is the southern 
 part of a larger embayment called La Babia de la Serena, and that south of it is a 
 small cove aptly named La Herradura, or the Horseshoe. Coquimbo Bay and La 
 Herradura were formerly united when the sea stood along the elevated beach-lines, 
 and they owe their actual basins to the currents that swept around the granite island 
 north of La Herradura. Non-deposition and submarine scour combined to prevent 
 them from being filled to the level of the deposits that accumulated in the lee of the 
 island and that now form the terrace which lies between them and connects the former 
 island with the mainland. The circular form of La Herradura is a very remarkable 
 example of current action. Coquimbo Bay owes its elongated shape to the trend of 
 the faulting in which it originated, and is modified in outline also by the ancient delta 
 of the Rio Elqui. 
 
 An extensive terrace fringes the base of the surrounding heights of the Coast 
 range and slopes toward the bays, to which the steeper descent steps down by benches 
 that vary greatly in width according to the conditions of erosion by the changing 
 currents as the land rose from its deepest submergence. Where the currents were 
 adequately strong they prevented or limited deposition. Beneath quieter waters fine 
 sediment gathered on the flat bottom. There has been but little subaerial erosion 
 since tbe sea-bottom was elevated, and it remains almost unchanged, bearing witness 
 to the recent occupation of the larger embayment by the sea, even as the marine 
 shells do. 
 
 101 
 
102 
 
 Earthquake Conditions in Chile 
 
 The strata of which the terraces are composed consist of sand and silt, with a 
 large proportion of shells, and some of them are cemented to hard limestone. Although 
 perfectly conformable in dip, they belong to several different periods, from Pliocene 
 to Present, and are associated with older formations. We may distinguish the fol¬ 
 lowing sequence of events: Late Paleozoic, intrusion of granite (older rocks not seen 
 in this vicinity) ; Mesozoic and probably Eocene Tertiary, uplift and erosion to the 
 extent of laying bare the granite, faulting possibly connected with the uplift; 
 Miocene ?, deposition of limestone against the exposed face of the granite on the fault 
 scarp (age not positively determined, possibly Pliocene) ; Pliocene, marked displace¬ 
 ment on the fault east of Coquimbo Point, depression of the block underlying Co- 
 quimbo Bay, and deposition of the sands and calcareous formation of the terraces, 
 continuing without recognized break into the Pleistocene; Early Glacial, distribu¬ 
 tion of large boulders, probably by floating ice; Later Pleistocene, continuation of 
 the subsidence and deposition of calcareous sands to the maximum extension of the 
 bay; Recent, retreat of the sea in consequence of elevation of the entire district, 
 producing a distinct disconformity marked by gravel beds and accumulations of shells 
 of species now living in the bay; Present, continued uplift without faulting. 
 
 The earlier events of this record may be passed over without discussion, since 
 they are not peculiar to the locality and their recognition does not depend upon any 
 observations pertinent to the description of Coquimbo Bay. The granite elsewhere 
 occurs beneath the Triassic of the Chilean coast and is therefore assigned by Felsch 
 to the Paleozoic. The erosion of overlying strata, including any that may have 
 been laid down on it in this vicinity, is complete. The first sedimentary rock which 
 is seen in contact with the granite is a limestone that has yielded one specimen of 
 Ostrea ingens Zittel and that may be of Miocene age. We may begin our description 
 with that occurrence. 
 
 In April 1923, the excavation at the northern end of the railroad yard, which is 
 located at the eastern base of the granite promontory on the extension of the main 
 street of Coquimbo, exposed blocks of limestone in contact with the granite. Some 
 of them were in place and consisted at the contact of calcareous sandstone a few 
 centimeters thick, followed by gray limestone of a much denser character than any 
 seen in the terrace deposits. The actual thickness seen amounted to about 1 meter. 
 The calcareous deposit penetrated the crevices of the steep slope and had evidently 
 been deposited against it. 
 
 A well-preserved specimen, since identified by Mr. Eric Jordan as Ostrea ingens 
 Zittel, was given me by the official in charge of the yard as having been taken from 
 the limestone. The evidence of Miocene or middle Pliocene age which it affords is 
 in keeping with the character of the rock as contrasted with the Pliocene of the ter¬ 
 race formation. 
 
 A fresh excavation, made while I was there and for the purpose of installing 
 a bumper at the end of the track, exposed an irregular displacement of the limestone, 
 which extended down into the granite. It was such a break as would occur in rocks 
 
Geology on Coquimbo Bay 
 
 103 
 
 at the surface, not under any load, at the outcrop of a fault. The fact that it went 
 down into the granite and inclined toward the hill precluded the alternative of a slide. 
 
 The displacement thus indicated is on the line of one of the upthrust faults traced 
 southward to Coquimbo and corresponds in its indications with the inferences confi¬ 
 dently drawn from the more general facts of the physiography of the region. The 
 scarp against which the limestone was deposited had been formed by faulting at some 
 earlier date. The fault, therefore, antedated the Miocene or middle Pliocene epoch 
 of deposition, but continued to be active at least into the Pliocene. 
 
 THE TERRACES 
 
 The terraces of Coquimbo were examined by Darwin in 1835 in the course of a 
 trip from Valparaiso to Huasco. He rode from point to point along the coast and 
 neighboring valleys, which he describes in his Journal with his characteristic atten¬ 
 tion to significant details. Regarding the terraces he wrote: 1 
 
 “ I spent some days in examining the step-formed terraces of shingle, first noticed by Captain B. 
 Hall and believed by Mr. Lyell to have been formed by the sea, during the gradual rising of the 
 land. This certainly is the true explanation, for I found numerous shells of existing species on these 
 terraces. Five narrow, gently sloping, fringe-like terraces rise one behind the other and where best 
 developed are formed of shingle; they front the bay and sweep up both sides of the valley. At 
 Guasco (Huasco), north of Coquimbo, the phenomenon is displayed on a much grander scale, so as 
 to strike with surprise even some of the inhabitants. The terraces are there much broader, and may 
 be called plains; in some parts there are six of them, but generally only five; they run up the valley 
 for thirty-seven miles from the coast. These step-formed terraces or fringes closely resemble those 
 in the valley of S. Cruz and, except in being on a smaller scale, those greater ones along the whole 
 coast-line of Patagonia. They have undoubtedly been formed by the denuding power of the sea, 
 during long periods of rest in the gradual elevation of the continent.” 
 
 In Darwin’s day the capacity of rivers to transport debris was underestimated, 
 the influence of climatic changes in causing them to erode what they had once built 
 up was not understood, and the analogy of the extraordinary fluviatile terraces of 
 South America with shingle beds forming in the fiords of southern Chile was strik¬ 
 ing. He was therefore led to set aside the evidence of river action in the valleys and 
 to ascribe all of the terrace deposits of the Andes, even those which now lie at great 
 elevations, to marine denudation and deposition. The undoubted marine terraces of 
 Coquimbo confirmed him in this generalization, although he himself observed the 
 mingling of marine and fluviatile deposits at the mouth of the Rio Elqui, where it 
 enters Coquimbo Bay. The river terraces are discussed elsewhere in this volume. 
 Darwin’s description of the marine terraces is not only of great interest as the record 
 of his observations, but is valuable in that it supplies many details of which the writer 
 either could not or did not take note. It is therefore quoted in full: 2 
 
 “ Coquimbo 
 
 “ A narrow fringe-like plain, gently inclined towards the sea, here extends for eleven miles 
 along the coast, with arms stretching up between the coast-mountains, and likewise up the valley of 
 Coquimbo: at its southern extremity it is directly connected with the plain of Limari, out of which 
 
 1 Charles Darwin, Journal of Researches into the Natural History and Geology of the Countries Visited 
 During the Voyage of H. M. S. Beagle Around the World, second edition, D. Appleton & Co., 1891, p. 343. 
 
 2 Charles Darwin, Geological Observations on South America, first edition, London, Smith, Elder & Co., 
 1846, pp. 36 - 4 1 - 
 
104 
 
 Earthquake Conditions in Chile 
 
 hills abruptly rise like islets, and other hills project like headlands on a coast. The surface of the 
 fringe-like plain appears level, but differs insensibly in height, and greatly in composition, in different 
 parts. 
 
 “ At the mouth of the valley of Coquimbo, the surface consists wholly of gravel, and stands 
 from 300 to 350 feet above the level of the sea, being about 100 feet higher than in other parts. In 
 these other and lower parts, the superficial beds consist of calcareous matter, and rest on ancient 
 tertiary deposits hereafter to be described. The uppermost calcareous layer is cream-coloured, com¬ 
 pact, smooth-fractured, sub-stalactiform, and contains some sand, earthy matter, and recent shells. 
 It lies on, and sends wedge-like veins into, 1 a much more friable, calcareous, tuff-like variety; and 
 both rest on a mass about twenty feet in thickness, formed of fragments of recent shells, with a 
 few whole ones, and with small pebbles firmly cemented together. This latter rock is called by the 
 inhabitants losa, and is used for building: in many parts it is divided into strata, which dip at an 
 angle of ten degrees seaward, and appear as if they had originally been heaped in successive layers 
 (as may be seen on coral-reefs) on a steep beach. This stone is remarkable from being in parts 
 entirely formed of empty, pellucid capsules or cells of calcareous matter, of the size of small seeds: 
 a series of specimens unequivocally showed that all these capsules once contained minute rounded 
 fragments of shells which have since been gradually dissolved by water percolating through the mass. 2 
 
 “ The shells embedded in the calcareous beds forming the surface of this fringe-like plain, at 
 the height of from 200 to 250 feet above the sea, consist of, 
 
 1. Venus opaca. 6. Monoceros costatum. 
 
 2. Mulinia byronensis. 7. Concholepas peruviana. 
 
 3. Pecten purpuratus. 8. Trochus (common Valparaisa spe- 
 
 4. Mesodesma donaciforme. cies). 
 
 5. Turritella cingulata. 9. Calyptnea Byronensis. 
 
 “ Although these species are all recent, and are all found in the neighbouring sea, yet I was 
 particularly struck with the difference in the proportional numbers of the several species, and of 
 those now cast up on the present beach. I found only one specimen of the Concholepas, and the 
 Pecten was very rare, though both these shells are now the commonest kinds, with the exception, 
 perhaps, of the Calyptrcca radians, of which I did not find one in the calcareous beds. I will not 
 pretend to determine how far this difference in the proportional numbers depends on the age of the 
 deposit, and how far on the difference in nature between the present sandy beaches and the calcareous 
 bottom, on which the embedded shells must have lived. 
 
 “ On the bare surface of the calcareous plain, or in a thin covering of sand, there were lying at a 
 height from 200 to 252 feet, many recent shells, which had a much fresher appearance than the 
 embedded ones: fragments of the Concholepas, and of the common Mytilus, still retaining a tinge 
 
 No. 8.-SECTION OF PLAIN OF COQUIMBO. 
 
 Surface of plain, 252 feet above sea. 
 
 B B 
 
 Fig, 6 —Section of Plain of Coquimbo (Darwin). 
 Level of sea. 
 
 A—Stratified sand, with recent shells in same proportions as on the beach, half filling up a ravine. 
 
 B—Surface of plain with scattered shells in nearly same proportions as on the beach. 
 
 D—LowYr C caf^areou S b ^ndy bed (Losa),} with recent shells > but not in same Proportions as on the beach. 
 E—Upper ferrugino-sandy old tertiary stratum, 
 
 F—Lower old tertiary stratum, 
 
 } 
 
 with all, or nearly all, extinct shells. 
 
 1 In many respects this upper hard, and the underlying more friable varieties, resemble the great superficial 
 beds at King George’s Sound in Australia, which I have described in my Geological Observations on Volcanic 
 Islands, p. 144. There could be 'little doubt that the upper layers there have been hardened by the action of rain 
 on the friable calcareous matter, and that the whole mass has originated in the decay of minutely comminuted 
 sea-shells and corals. 
 
 2 I have incidentally described this rock in a note, p. 145, of the above work on Volcanic Islands. 
 
Geology on Coquimbo Bay 
 
 105 
 
 of its colour, were numerous, and altogether there was manifestly a closer approach in proportional 
 numbers to those now lying on the beach. In a mass of stratified, slightly agglutinated sand, which 
 in some places covers up the lower half of the seaward escarpment of the plain, the included shells 
 appeared to be in exactly the same proportional numbers with those on the beach. On one side of a 
 steep-sided ravine, cutting through the plain behind Herradura Bay, I observed a narrow strip of 
 stratified sand, containing similar shells in similar proportional numbers: a section of the ravine is 
 represented in the following diagram, which serves also to show the general composition of the 
 plain. I mention this case of the ravine chiefly because without the evidence of the marine shells in 
 the sand, any one would have supposed that it had been hollowed out by simple alluvial action. 
 
 “ The escarpment of the fringe-like plain, which stretches for eleven miles along the coast, is in 
 some parts fronted by two or three narrow, step-formed terraces, one of which at Herradura Bay 
 expands into a small plain. Its surface was there formed of gravel, cemented together by calcareous 
 matter; and out of it I extracted the following recent shells, which are in a more perfect condition 
 than those from the upper plain : 
 
 1. Calyptraea radians. 
 
 2. Turritella cingulata. 
 
 3. Oliva peruviana. 
 
 4. Murex labiosus, var. 
 
 5. Nassa (identical with a living species). 
 
 6. Solen dombeiana. 
 
 7. Pecten purpuratus. 
 
 8. Venus chilensis. 
 
 “ On the syenitic ridge, which forms the southern boundary of Herradura Bay and Plain, 
 I found the Choncholepas and Turritella cingulata (mostly in fragments) at the height of 242 feet 
 
 9. Amphidesma rugulosum. The small 
 irregular wrinkles of the posterior 
 part of this shell are rather stronger 
 than in the recent specimens of this 
 species from Coquimbo. (G. B. 
 Sowerby.) 
 
 10. Balanus (identical with living species). 
 
 No. 9.- EAST AND WEST SECTION THROUGH THE TERRACES AT COQUIMBO, WHERE THEY 
 
 DEBOUCH FROM THE VALLEY. AND FRONT THE SEA.' 
 
 (F) 
 
 364feet 
 
 
 (E) 
 
 302 
 
 (C) 
 
 120 
 
 (B) 
 
 70 
 
 Sea Level 
 
 (A) 
 
 25 
 
 £sst Town of Coquimbo West 
 
 Fig. 7 — Section through terraces at Coquimbo. 
 
 Vertical scale T V of inch to 100 feet: horizontal scale much contracted. 
 
 above the sea. I could not have told that these shells had not formerly been brought up by man, if I 
 had not found one very small mass of them cemented together in a friable calcareous tuff. I mention 
 this fact more particularly, because I carefully looked, in many apparently favourable spots, at lesser 
 heights on the side of this ridge, and could not find even the smallest fragment of a shell. This is 
 only one instance out of many, proving that the absence of sea-shells on the surface, though in many 
 respects inexplicable, is an argument of very little weight in opposition to other evidence on the 
 recent elevation of the land. The highest point in this neighbourhood at which I found upraised shells 
 of existing species, was on an inland calcareous plain, at the height of 252 feet above the sea. 
 
 “ It would appear from Mr. Caldcleugh’s researches 1 that a rise has taken place here within 
 the last century and a half; and as no sudden change of level has been observed during the not very 
 severe earthquakes, which have occasionally occurred here, the rising has probably been slow, like 
 that now, or quite lately, in progress at Chiloe and at Valparaiso: there are three well-known rocks, 
 called the Pelicans, which in 1710, according to Feuillee, were a Hour d J eau, but now are said to stand 
 twelve feet above low water-mark; the spring-tides rise here only five feet. There is another rock, 
 now nine feet above high water-mark, which in the time of Frezier and of Feuillee rose only five or 
 six feet out of water. Mr. Caldcleugh, I may add, also shows (and I received similar accounts) that 
 there has been a considerable decrease in the soundings during the last twelve years in the Bays of 
 Coquimbo, Concepcion, Valparaiso, and Guasco; but as in these cases it is nearly impossible to dis¬ 
 tinguish between the accumulation of sediment and the upheavement of the bottom, I have not entered 
 into any details. 
 
 " Valley of Coquimbo —The narrow coast-plain sends, as before stated, an arm, or more cor¬ 
 rectly a fringe on both sides, but chiefly on the southern side, several miles up the valley. These fringes 
 
 1 Proceedings of the Geological Society, Vol. II, p. 446. 
 
106 
 
 Earthquake Conditions in Chile 
 
 are worn into steps or terraces, which present a most remarkable appearance, and have been compared 
 (though not very correctly) by Capt. Basil Hall, to the parallel roads of Glen Roy in Scotland: their 
 origin has been ably discussed by Mr. Lyell. 1 The first section which I will give, is not drawn across 
 the valley, but in an east and west line at its mouth, where the step-formed terraces debouch and 
 present their very gently inclined surfaces towards the Pacific. 
 
 “ The bottom plain (A) is about a mile in width, and rises quite insensibly from the beach to a 
 height of twenty-five feet at the foot of the next plain: it is sandy and abundantly strewed with 
 shells. 
 
 “ Plain or terrace (B) is of small extent, and is almost concealed by the houses of the town, 
 as is likewise the escarpment of terrace (C). On both sides of a ravine, two miles south of the town, 
 there are two little terraces, one above the other, evidently corresponding with B and C; and on them 
 marine remains of the species already enumerated were plentiful. Terrace (E) is very narrow, but 
 quite distinct and level; a little southward of the town there were traces of a terrace (D) interme¬ 
 diate between (E) and (C). Terrace (F) is part of the fringe-like plain, which stretches for the 
 eleven miles along the coast; it is here composed of shingle and is ioo feet higher than where com¬ 
 posed of calcareous matter. This greater height is obviously due to the quantity of shingle, which at 
 some former period has been brought down the great valley of Coquimbo. 
 
 “ Considering the many shells strewed over the terraces (A) (B) and (C), and a few miles 
 southward on the calcareous plain, which is continuously united with the upper step-like plain (F), 
 there can not, I apprehend, be any doubt, that these six terraces have been formed by the action of the 
 sea; and that their five escarpments mark so many periods of comparative rest in the elevatory move- 
 
 No. IO. - NORTH AND SOUTH SECTION ACROSS THE VALLEY OF COQUIMBO 
 
 Fig. 8 —North-south section across valley of Coquimbo (Darwin). 
 
 Vertical scale A of inch to ioo feet; horizontal scale much contracted; terraces marked with (?) do not 
 occur on that side of the valley, and are introduced only to make the diagram more intelligible. A river and 
 bottom-plain of valley; C, E and F, on the south side of valley, are respectively, 197, 377 , and 4 20 feet above the 
 level of the sea. 
 
 ment, during which the sea wore into the land. The elevation between these periods may have been 
 sudden and on an average not more than seventy-two feet each time, or it may have been gradual 
 and insensibly slow. From the shells on the three lower terraces, and on the upper one, and I may 
 add on the three gravel-capped terraces at Conchalee, being all littoral and sub-littoral species, and 
 from the analogical facts given at Valparaiso, and lastly from the evidence of a slow rising lately or 
 still in progress here, it appears to me far more probable, that the movement has been slow. The 
 existence of these successive escarpments, or old clifif-lines, is in another respect highly instructive, 
 for they show periods of comparative rest in the elevatory movement, and of denudation, which 
 would never even have been suspected from a close examination of many miles of coast southward 
 of Coquimbo. 
 
 “We come now to the terraces on the opposite sides of the east and west valley of Coquimbo: 
 the following section is taken in a north and south line across the valley at a point about three miles 
 from the sea. The valley measured from the edges of the escarpments of the upper plain (F) (F) 
 is about a mile in width ; but from the bases of the bounding mountains it is from three to four miles 
 wide. The terraces marked with an interrogative do not exist on that side of the valley, but are 
 introduced merely to render the diagram more intelligible. 
 
 “ A A The bottom of the valley, believed to be 100 feet above the sea: it is continuously united 
 with the lowest plain (A) of the former section. 
 
 “(B) This terrace higher up the valley expands considerably; seaward it is soon lost, its 
 escarpment being united with that of (C) : it is not developed at all on the south side of the valley. 
 
 “(C) This terrace like the last, is considerably expanded higher up the valley. These two ter¬ 
 races apparently correspond with B and C of the former section. 
 
 “(D) is not well developed in the line of this section; but seaward it expands into a plain; it is 
 not present on the south side of the valley; but it is met with, as stated under the former section, a 
 little south of the town.” 
 
 1 Principles of Geology (1st edit.), Vol. Ill, p. 131. 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 if 
 
 54 
 
 14 
 
 12 
 
 11 
 
 20 
 
 27 
 
 30 
 
 16 ” 23 31 
 
 26 
 
 1219 21 29 
 
 29 
 
 30 
 
 .{VA7 » 
 
 19: 4. ( Outer Pataros 
 •' 27 27 
 
 13 /.*. /18 20 27 25 
 
 17 
 
 16 34 
 
 25 
 
 12 
 
 11/ 
 
 21 
 
 al: -.:?8 14 2 P A j Xros 26 
 
 26 
 
 21 ; 
 
 19 
 
 la ,, f1304JH, 24 
 
 20 
 
 24 
 
 24 
 
 19 n ROCKS 
 
 * 14 25 
 
 24 
 
 11 
 
 23 
 
 19 
 
 23 
 
 24 
 
 17 
 
 22 a 21 IS 
 
 hJ 01 
 
 22 21 2B y* 8 
 
 14 1^ ,10. >7^- 7; ,7® Kfc 19 17 
 
 lo¬ 
 
 se 
 
 21 13 15 ** 21 
 
 27 .» 10 12 
 
 j. Pajaroa iXiios ^js 22 
 
 30 26 l«, 17 
 
 Pileartios Rk* .:•;!*.4.10 in 17 rky.S li; 
 
 9/7# su , 17 >7 lb 
 
 19 7 • 21 is rky 
 
 16 '•"•14 W 
 
 22 „ _ _ 
 
 la +tJ Light fl ashing whiteM G 1 8 ' 1& 38 
 
 ?* ±l 17 7 every 2 seconds <**, !j.» IS 14 
 
 18 
 
 , Of 
 
 rHis 
 
 17 
 
 17 
 
 s5sr 
 
 33 12 io 
 
 Jrf.SA / 
 
 10 
 
 U / 
 
 5A 
 
 13 lo'l I0r.i «’ 
 
 > '~ r Tort 11 da Pt 30 12 “» ~ 
 
 4 11 '''AX vA^ 2 T 2 >« £ 15 ^ 
 
 ^<1^15 10 
 
 Jf.S 
 
 25 
 
 25 23 . 6 A®_ 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 IO 
 
 14 
 
 16 15 14 
 
 35 
 
 Sh ,X S 17 20 17 
 
 12 
 
 M 
 
 l» Ht Z0 SJ* is 
 
 14 
 
 17 
 
 30 
 
 17 1 
 
 14 
 
 i612 8 ; 
 
 flash02 secteclipse I 8sec L j 
 90ft vis.10 m. 
 
 12 
 
 • i 6 | 8 7 
 
 -o v . 
 
 S aliefi'ig 5 
 
 39 j~ 
 
 64 \ 12 
 
 13 
 
 30 
 
 38 
 
 ' 
 
 13 13 
 
 12 
 
 , 44 io 12 
 
 Chalet/. -. 
 
 (Conapioj ‘ f % -3 10 ,-'12 11 12 
 
 H 4 *£tf ,S * 
 
 V. Abta^’ '***- 
 
 12 
 
 6? < 
 
 11 
 
 6? Gi 
 
 30 
 
 30 
 
 .20 
 
 30 
 
 26 
 
 30 
 
 0BS | P a °^ Ohs Point 9 0a 
 
 '?/#’ £ ,V C°nspic Clumprra JVff, & l 8 9 8 „ 
 
 'A ■ 4 405 f -*£ ^ 8 
 
 Mkk^rl 1 
 
 C O Q U I'M BO B A Y 6 j « 
 
 -- -_-19 ' fl 9 6 7 4 
 
 6i 6 5 * 
 
 7 7 67 
 
 &2 
 
 1 5i 
 
 42 
 
 30 
 
 25 16 /it! 
 
 26 
 
 , 1 
 
 20 
 
 IT ,y 
 
 14 ^. U 6 v*7 
 
 i 7 * 8 8 
 
 jf-JI^O&QalPierl 1 , 7 - 
 
 ,. , «>a 
 
 t>$ 
 
 62 # 6 i J/.S 
 
 1 65 - 6 4 7 6 5 3 
 
 > 5 , „i ACS 4 5i 
 
 !. si 8 * ei « 62 62 
 
 i. 5j. .. -i. 
 
 andmu Flac e •I 
 
 6 4 8 ; 3 45 4 
 
 5| 4^ ^ ^ 
 
 64 5 2 • ,3 4 .1 
 
 *iS s 4 * 44 45 
 
 3? 1 
 
 ,5 -as..- 4 J ,.-•••-•••;’ 
 
 J Mfatf»pan*n*riaee <t 4 . ~T. . ... ... 4* 4v .P 75 
 
 W 3 k^\? 4 45 4 a ^ 4 ^ ^ 4 2 ? * 
 
 3b 
 
 15 
 
 *16 
 
 30 TiiiaiaPt^i 
 
 
 4 1 
 
 
 30 
 
 30 
 
 L/f, 
 
 30 
 
 20 
 
 ., vOOUDCB 
 
 Jospital. . CUvircti Spire? 
 
 FENINS.UL^V^ I' 
 
 i * \ J M M 3 
 
 ' v aSglOwf^ii i-i i? 
 
 nnr* ^ hi if 
 
 fc ^ AS 
 
 tee Ccutsec 
 an d . 
 
 3 3* 3 Is: Y 3 — 
 
 I3t 3i **;»■ r.^: v »C,.i 4 ,r ^■■••3 34 3i 2i 3 it 
 
 sr*?** 6 4 e 
 
 2i 2 i 
 
 u /rx- 
 
 n- 2 
 
 , 25. 2 2 
 
 2 ,3 li 
 
 17 
 
 2 ? 
 
 2 
 
 30 
 
 30 30 -/ 
 
 21 
 
 19 
 
 "--•la 
 
 3n 30 
 
 ..30 22 17 
 
 Drill ^roun 
 
 \ - ' : P je*t 
 
 tail ••• /; 
 
 z? m: 
 
 ** n 2 . . . ... 
 
 ll 
 
 - .. 
 
 . :9 5 >- 4 1 ' ^ 
 
 , i i 1 7 -- 2 j 5 4 
 
 9 . 4 ■> -•_ 
 
 tffWFWWrtfr- 
 
 6 Of 
 
 /l‘\li U lg —'"V.,,,!:* 1 
 
 .30 
 
 30 
 
 IS . 
 
 . 65 1 ' 
 
 30 
 
 3-0 16 
 
 Flayn 111 art o a ~ 
 
 SbMieaoF^JV-^ 325 • 7 ^'^' 
 
 28 3 iftlta S ^ 
 
 11 n iX ^ 28 
 
 flerradural’t;.Ji u 7 30 30 
 
 22 
 
 23 
 
 HospilaK 4 
 Ceil 
 
 PooniDa 
 
 .. -» . as* 
 
 xbr'6 4 ©■"" 
 
 *5 ©P's-? 
 
 Ra.dio.,^t^L.° 
 
 
 13 
 
 21 
 
 -v a'u*’ 
 
 25 9 10 
 
 ~r*‘ 12oCfexyfeAleA 
 
 8 'x_//'l 
 
 Spire 
 
 ^ is ‘‘’ 8 "\C r ' 4 V^S|^^\\|k VAVACAW 
 / “» » fjf \V®&V 
 
 ^ IP 38 IS “ 12 9 4,S> -^4 
 
 v'— V#h 20 14 12 10 *&- 
 
 p a s"Woii^ 4 ’ 
 
 .V' 
 
 
 Ithilea 
 
 * ‘-«. N 
 
 
 00 17 16 
 
 • 14 13 
 
 
 / 
 
 / IW Cl S - / X J ,7 14 13 _ 3f 10 8 ,.3 :< »* “ 
 
 & { 14 13 U 7 ; 'll J fllfe . J 
 
 f 9 . v \/** £ ** AI >& R * / 4 . (i 22/ IJ f 
 
 12 
 
 PORT 
 
 4 , ‘ 1 * V4 * 
 
 ^ if 
 
 34 8 
 
 8 fi9 / .1 m 
 
 6? 6 4 /..l PC / 
 
 
 . • 
 
 .-•• .-v . 
 
 o' 
 
 •v JL-$a 
 
 7 7 f”- s : SK r« 7 /.: 
 
 ...... ,/ s . 4/ , partially \4 
 
 I V? 4 8 il/'/V R 44 b 24 ::a- cultivated \p, v 
 
 /i 2 3 2? 2 ? -X.,.3' 2 i ,5 ttfiMai 
 
 .X 
 
 
 ■Mi/ II 7 n s.st 15 ., r "’ O 
 m 2 - 15 2 2 ; ^ 
 
 
 f/W 
 
 K . } ..♦ 
 
 1 - Z rpWhale • 
 
 I ^Mii-oirtar 4 
 
 \ o ^WTells 
 
 r" 03 SI ^oo 3 wa.tei' ) \ x, Sv 
 
 8 r: - g Herr a dura. "V \ 
 
 ° a o„ t) 
 
 A. Hoen & Co. Lith. 
 
 CHART OF ( 
 
Plate LV 
 
 Cerro Grande 
 
 t B aena. Vista.) 
 
 1660 
 
 Abt&Oft 
 
 SOUTH AMERICA 
 
 AND 
 
 PORT 
 
 HER RAD URA 
 
 Original British Survey in 1868. 
 
 With additions from a French Survey in 1853 
 
 Observation Spot ©.Lat.29 ° 56'24" S. Long. 71° 21 53" W. 
 H.W.EAC.lXh.OCm._Spriii^ tides rise S feet 
 
 SOUNOINGS IN FATHOMS 
 HEIGHTS IN FEET 
 
 M.mu<i■ S. jtftrtfi.Sh^.’sheiLs. St-ston**. dJc. linr/c. r/cy. rocky 
 
 . ::v- 1 « 
 
 .ui. V>> ' 
 
 -55' 
 
 — 5 T 
 
 -59’ 
 
 Part of Hydrographic Office. U. S. N. Chart No. 1326. 
 
 QUIMBO BAY 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Geology on Coquimro Bay 
 
 107 
 
 The writer’s observations on the terraces were confined to the immediate vicinity 
 of Coquimbo and the bluffs along the Arroyo Gulebran, a ravine which enters the 
 bay from the east, opposite to the town. He concentrated on the stratigraphy of the 
 marine terrace deposits and the evidences of beach-lines on Coquimbo point. Detailed 
 descriptions of specific localities follow. (Plate LV.) 
 
 Fig. 9 —Section of bluff at mouth of Quebrada 
 Gulebron, Coquimbo. 
 
 Meters 
 
 Top, fine, gray-brown, sandy soil. I 
 
 Sand, crossbedded, with boulder. 
 
 Sand, with many fresh, perfect shells, and fragments 
 
 Sand, pebbles and boulder. 
 
 Disconformity. 
 
 Gray sand, weathering yellow, with four irregular but practically level layers of cemented shells; shells 
 
 dissolved, many casts. 1.80 
 
 Ferruginous gray sand, weathering yellow. 2.00 
 
 7-30 
 
 Bottom not exposed, just above tidal marsh. 
 
 My notes read: “ The basal sand contains weak iron concretions, but no fossils; it is not evidently stratified; 
 is wet and covered with an efflorescence. 
 
 The shell layers are irregular, exhibit many hollows, and are in part cemented to hard limestone. The shells 
 are broken; the number of fragments is large and many retain the sculpture, but there are also many casts from 
 which the shells have been dissolved. 
 
 The gravel and cobbles lie upon an eroded surface, washed by the waves of a retreating sea and covered with 
 its detritus. 
 
 Before entering the bay the Arroyo Gulebron is crossed by the railroad, and 
 above that point meanders in a broad meadow. The meadow is bounded by bluffs of 
 stratified sands and limestone layers, rising successively higher to the levels of the 
 terraces as they recede toward the hills. It is evident that the Gulebron has corraded 
 its channel in the strata and that the bluffs expose sections of the sediments that were 
 once laid down continuously from side to side of the present valley. It is not equally 
 
108 
 
 Earthquake Conditions in Chile 
 
 certain that the terrace fronts around the bay represent eroded scarps of subaerial 
 origin. They may have been shaped by currents during or subsequent to deposition, 
 and they may have received later deposits on their surfaces. The first inspection of 
 the plan of the terraces, particularly of Herradura Cove, suggested that these latter 
 conditions had probably existed, and supporting evidence was found in the stratigra¬ 
 phy. The study was not, however, exhaustive, and it is possible that the seemingly 
 simple terrace deposits include other disconformities in addition to those which I 
 found. 
 
 Immediately east of the crossing of the Gulebran by the railroad is a bluff 26 
 feet (8 meters) high. Its base is of yellow sand; there is a capping of harder sands 
 with limestone layers, and the top consists of sands with gravel and cobbles. The 
 detailed section, which is sketched in figure 9 from field notes, is shown on page 107. 
 
 The conclusion stated in the last paragraph followed from the examination of 
 the section in detail. It was not anticipated, but was suggested by the very evident 
 difference in the shells above and below the contact. Those above retained their color 
 as freshly as any washed on the beach a few weeks before. Those below had long 
 been subjected to the action of filtering waters, which had both dissolved and cemented 
 them. The cobbles also were foreign to the lower sediments and indicated a change. 
 
 Seeking to extend the observations, I went north and east along the slope skirt¬ 
 ing a meander of the Arroyo Gulebron. There were no exposures for a distance of 
 some 2,000 feet (600 meters) ; nothing but loose sand and brush; then a slight reen¬ 
 trant angle which ended in a vertical chimney gave a section 65 feet (20 meters) high. 
 The detailed section was: 
 
 Level of outer edge of terrace; terrace slopes north i° io' toward the bay. Meters 
 
 Sand with fresh shells, large Pectens. 7 
 
 Gravel at the contact. 
 
 Limestone . 1.5 
 
 Sand with Pectens . 11.5 
 
 20.0 
 
 Raised edge of meadow. 
 
 The lower sands in this exposure were strongly cross-stratified. They were wind- 
 drifted sands, blown against the eroded face of the cliff, which they obscured, except 
 at the projecting limestone ledge. The little chimney in the sands had been washed 
 out in some recent rain and the stormwaters had carried down the large Pectens, 
 which were scattered on the surface or buried on edge. 
 
 It seems not improbable that an occurrence of this kind was observed by Darwin, 
 who described and sketched it as the recent result of deposition by the retreating sea, 
 which had cut out the ravine by the force of the waves and currents, according to the 
 hypothesis entertained in his day. 
 
 Eastward from the last observation, for a space of 1,650 feet (500 meters), the 
 surface slopes consisted of wind-blown sands, obscuring all the marine deposits, but 
 beyond that point there were precipitous bluffs. At one of these the section, on page 
 109, 190 feet (57 meters) high, was measured. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LVI 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LVII 
 
 A. Coquimbo. Qucbrada Gulebron, Marine Pliocene at base of cliffs. 
 
 P>. Coquimbo. Quebrada Gulebron. Secondary limestone capping upper 
 terrace; described by Darwin as “ losa.” 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LVIII 
 
 A. Coquimbo. Quebrada Gulebron. Upper terrace near Estancia San Martin, showing upper 
 horizon of erratics in marine strata: the lower horizon is just below the bottom of the view. 
 
 B. Coquimbo. Quebrada Gulebron. Cliffs on south side showing large erratic in marine strata 
 
 in center of view. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LIX 
 
 A. Coquimbo. Pliocene, marine strata with embedded erratic ; the tripod is one meter long; 
 looking south at cliffs south of the Quebrada Gulebron. 
 
 B. Coquimbo. Near view of same large erratic in Pliocene strata south of Quebrada Gulebron. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LX 
 
 A Coquimbo. Quebrada Gulebron. Rock 
 
 gorge from which erratics were presumably derived. 
 
 B. Coquimbo. Quebrada Gulebron. South bank in which erratics occur embedded : very large 
 erratic in foreground; about 23 feet long by 12 feet high (7 meters by 4 meters). 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXI 
 
 A. Coquimbo. Looking south past the curve of La Herradura cove. Large boulder buried in 
 marine Pliocene on the terrace ioo feet above sea, 1.5 miles west of the Quebrada Gulebron. 
 
 P>. Coquimbo. Marine strata with embedded boulder ; locality in the railroad cut east of 
 
 La Herradura cove. 
 
Geology on Coouimbo Bay 
 
 109 
 
 The sands in the above section were all marine, as is shown by the abundant fos¬ 
 sils which they contain. The limestones were also marine deposits. They too contain 
 
 Section of Marine Pliocene in Bluff North of the Arroyo Gulebron, Half a Mile East of the Railroad 
 
 [Fossils were collected from the strata marked with roman numerals and are described in 
 the report by Eric Jordan under the same numbers.] 
 
 Front of lower, high level terrace: Meters 
 
 Sand, fine, brown, and earthy. 2.0 
 
 Calcareous sand and pebbles. 0.5 
 
 Sand . 3-5 
 
 Cemented shell bed, coquina with pebbles. 0.5 
 
 Sand . 3 0 
 
 Coquina, III, included with I and II. 2.0 
 
 Sand . 3-0 
 
 Coquina with pebbles . 4 0 
 
 Sand . 6.0 
 
 Coquina in two benches. 3.0 
 
 Sand . 2.5 
 
 Coquina . 1.0 
 
 Pebble layer . 0.2 
 
 Coquina . 0.4 
 
 Sand . 0.8 
 
 Coquina . 0.2 
 
 Sand . 0.3 
 
 Coquina, II . 2.5 
 
 Sand, I . 1.0 
 
 Slope of loose sand. 20.0 
 
 Level of meadow. - 
 
 Thickness . 56-4 
 
 numerous fossils; they are distinctly stratified with the sands; and they do not exhibit 
 the textures or inclusions which are found in the subaerially concentrated lime for¬ 
 mation that caps the uppermost terrace. The section thus seems to record a continu- 
 
110 
 
 Earthquake Conditions in Chile 
 
 ous subsidence of the block on which the sediments were laid down, rather than any 
 alternation of rise and fall of land or sea. The conditions that determined the forma¬ 
 tion of coquina or the deposition of less calcareous sands escape our analysis, but 
 may probably have resulted from minor rhythms of climatic changes and of the living 
 conditions in the bay, in which winds and ocean currents played their part. (Plate 
 LVI.) 
 
 A careful field inspection failed to show any difference in the fossils contained in 
 the different horizons of this section. Jordan did not recognize any distinction 
 between the few forms obtained from the horizon III and those collected from the 
 two lower strata at the very bottom of the section. The whole fauna appeared to 
 correspond with the Cape Fairweather Pliocene. It is not impossible, however, that 
 more careful collecting by an experienced paleontologist may indicate changes cor¬ 
 responding to a passage from middle to later Pliocene or even to Pleistocene. My 
 collections were by no means exhaustive and the material secured was not satisfac¬ 
 tory. The collecting is difficult, the coquina being very hard, the sands very soft and 
 friable, and the shells generally large. The fossils do not break out of the coquina, 
 and they do not hold together in the sands. A mass of sand which was inclosed in 
 plaster of Paris at the place where it was excavated had dried out and crumbled to 
 loose debris before it reached the laboratory. In view of the classic interest attaching 
 to the locality and the opportunity which it affords to fix the dates of beginning and 
 ending of the subsidence, a thorough investigation is desirable, with intensive study 
 on the spot. 
 
 The absence of Recent shells from the uppermost strata of this section marks it 
 as less complete than the one observed at the bluff near the railroad and suggests that 
 the retreat of the sea had been accomplished earlier at this point. 
 
 The meadows of the Arroyo Gulebron terminate a short mile south of the bay, 
 where the stream comes out of a rocky canyon. (Plate LIX.) The outcrops of 
 old igneous rock are capped on both sides by the highest terrace of marine sedi¬ 
 ments, corresponding to the one designated (F) by Darwin, that is, to the terrace 
 which is continuous with the highest levels of the adjacent valleys in the coastal 
 mountains. It is upon this terrace that the “ losa ” or secondary limestone is strongly 
 developed. 
 
 It is striking evidence of the keenness of Darwin’s observation and analysis that 
 he recognized the secondary character of the massive limestone stratum which is 
 extensively developed on the upper terrace and goes by the Spanish term “ losa ” or 
 “caliche.” It varies from 3 to 6 feet (1 to 2 meters) in thickness, contains many 
 marine shells, probably of Pleistocene or Recent age, and is firmly cemented. The 
 essential condition of its development is the rise and evaporation of ground-water 
 charged with lime, and as this is variable, the occurrence of the superficial formation 
 is correspondingly irregular. It is very strongly developed just south of the Quebrada 
 Gulebron and the Estancia San Martin, and forms great slabs where it is undermined 
 on the edge of the bluff. (Plate LVII B.) The principal interest attaching to this for¬ 
 mation is the age of its fauna. It represents the farthest advance of the sea, and 
 
Geology on Coquimbo Bay 
 
 111 
 
 consequently the turning-point at which subsidence gave place to elevation. It will be 
 seen by reference to Jordan’s report on the collections which I was able to make that 
 the differences between the Pliocene and Pleistocene faunas in this region are not 
 readily detected, except by exhaustive and thorough study, for which this reconnais¬ 
 sance offered no opportunity. If, as seems probable on the evidence of the great 
 erratics embedded in the shell deposits at a lower level, the terrace formation includes 
 the early Pleistocene as well as the Pliocene, then we have the subsidence extending 
 into the latter epoch and must date the elevation from a time succeeding the earliest 
 glaciation. 
 
 The evidence of the erratics which occur in the shell deposits south of the Oue- 
 brada Gulebron, and particularly on the slopes north of the Estancia San Martin, 
 presents a problem which requires further investigation. One is puzzled to know how 
 boulders of such size as are found in the evenly stratified shell beds could have been 
 transported and dropped where they lie. They are also widely distributed over the 
 floor of the ancient bay and along the coast of the island that now forms Coquimbo 
 Point. Some agency which was active on the shores and in the bay itself was com¬ 
 petent to carry boulders 8 or io feet (2 or 3 meters) in diameter to distances of a mile 
 or more from their source in the canyon of the Gulebron or on the slopes of the old 
 island. 
 
 The facts of occurrence in the terraces above the Gulebron meadows are as fol¬ 
 lows: No boulders of any notable size were seen on the northern side of the Que- 
 brada. On the southern side there is a precipitous cliff with a cascade of the inter¬ 
 mittent stream which flows from the Estancia San Martin. The strata of this section 
 are more firmly cemented than they are on the north, and thus have the appearance 
 of greater age, but they are continuous and the induration is a local accident. About 
 60 feet (20 meters) below the top of the cliff is a layer which contains a number of 
 large rocks completely surrounded by the deposits of shells. The rocks rest on strata 
 composed of shells, are covered by shells, and in some cases even have barnacles 
 adhering to them. They are thus integral elements of the deposit. A second horizon 
 marked by boulders of smaller sizes occurs about 30 feet (10 meters) higher. 
 
 The size of the embedded rocks is that of boulders which would be among the 
 largest moved by a torrential stream on a steep grade. That agency of transporta¬ 
 tion is, however, excluded by the fact that they were deposited in marine waters, 
 where nothing stronger than a shore current could have existed. It might be sug¬ 
 gested that they represented the outwash of a torrent formed by a cloudburst or 
 similar accident, but they are not associated with the deposits of mud which in that 
 case should accompany the boulders, and their distance from the rock slope, which 
 is about a mile, is such that the force of a torrential current would have been ex¬ 
 hausted before they could have reached their present position. The boulders under 
 discussion are shown in Plates LVIII-LX. 
 
 The stratification of the shell-beds, the embedding of the boulders, and their size 
 are clearly distinguishable. It will also be noted that they are sharply angular and 
 exhibit no signs of stream abrasion. 
 
112 
 
 Earthquake Conditions in Chile 
 
 The erratics are all of one kind of rock, a dark, fine-grained igneous rock, prob¬ 
 ably a diabase, which outcrops in place in the canyon of the Quebrada Gulebron from 
 a half mile to a mile from the points at which they now lie. Their occurrence at one 
 horizon, embedded in marine shells, appears to limit the agency of their transporta¬ 
 tion to marine currents, and it would be consistent with the general direction of cur¬ 
 rents such as probably existed in the ancient day that the rocks should occur where 
 they do, on the south side of the Quebrada, since the principal sweep of the winds and 
 waves was from the north. It is, however, clearly beyond the power of any marine 
 current to transport rocks of this size unless they were floated. 
 
 Two agencies of flotation may be imagined. One would consist of rafts of tree 
 trunks carrying the rocks in their roots, the other is ice. There remains absolutely 
 no evidence of either, and we are left to conjecture on the basis of probabilities. 
 
 The suggestion that the rocks may have been carried by floating tree trunks is 
 put to rather a severe test by their size. It would require a large trunk, or a raft of 
 them, to support a boulder 6 feet (2 meters) across, and some of these exceed that 
 dimension. On the climatic side it appears improbable that the coasts of the Desert 
 of Atacama have supported trees of sufficient size to do the work, and there is no evi¬ 
 dence of the existence of such forest growth. If it occurred it was probably restricted 
 to trees in the canyon, like the red-wood groves on the coast of California. 
 
 On the other hand, the occurrence of ice in the form of heavy floes could occur 
 in latitude 30° on the shores of the Pacific Ocean only during a glacial epoch, and even 
 then only under exceptional local conditions. It would be unreasonable to postulate 
 any general development of such ice masses. Their local occurrence, however, seems 
 not improbable and would explain the facts presented by the boulders without de¬ 
 manding unreasonable assumptions. 
 
 It is of course a fact that the glacial epochs are represented by some sort of 
 record, either in the terrace deposits of Coquimbo Bay or in the sculpture of their 
 surfaces. The extremely recent character of the shell deposits on the bluff at the 
 mouth of the Quebrada Gulebron indicates that the land stood at least 30 feet (10 
 meters) lower within the present biologic episode of time. It is not beyond the recog¬ 
 nized effects of uplift to assume that it may have been raised 300 feet (100 meters) 
 since the middle Pleistocene, and the accumulation of 65 feet (20 meters) of shell 
 deposits is within the effects of deposition of a small part of the period. These are 
 the changes which have taken place since the deposition of the large erratics in the 
 terrace formation, and the estimate would carry 11s back to the early Pleistocene. 
 
 Evidences of glaciation in the Andes are described elsewhere in this report. They 
 indicate that the early Pleistocene was a time of the maximum expansion of glacia¬ 
 tion in the Cordillera and was marked by glaciers in localities which now stand 10,000 
 feet (3,000 meters) or more above sea in this or warmer latitudes. It also appears 
 that there was a later, less extensive glaciation, at least farther south. The ice never 
 approached the sea and we can not attribute any direct effect to glaciation along the 
 coast, but it is probable that the climate was severe, at least in winter, even at sea- 
 level. 
 
Geology on Coquimbo Bay 
 
 113 
 
 Recognizing these conditions, I would suggest the following hypothesis to 
 account for the transportation of the erratics: The Quebrada Gulebron, though not 
 so deep as at present, was a rock-walled ravine which lay in the shadow of the hills 
 where it skirts the first range above the terraces in descending from the valley in the 
 Coast range. The winter climate was sufficiently cold and precipitation sufficiently 
 heavy to produce banks of snow and ice in sheltered places, and during exceptional 
 successive seasons the summers were too short and chill to melt them. The winds 
 blew the snow from the terrace levels and drifted it into the ravine, and thus there 
 accumulated in the narrows of the Quebrada Gulebron a miniature glacierette. 
 During seasons of high floods masses of ice from the ravine were floated out over 
 the bay, carrying with them the erratics which now present the anomalous evidence 
 of cold climate. This occurred at two levels, possibly in conjunction with the two 
 glaciations. The hypothesis must be extended to cover the effects of ice on Coquimbo 
 Point, which are yet to be described, and to account for the large boulders that lie 
 on the terrace east of La Herradura. These imply that the climate must have been 
 so severe that some coast ice formed in sufficient masses to afford local transporta¬ 
 tion. The episode, however, was singular, for the erratics deposited on the terrace 
 seem to be limited to a single horizon. They do not appear to be repeated. It would 
 seem, therefore, that we have to deal with a phenomenon which was the result of 
 unusual conditions and was abnormal, even for the glacial epoch. The reader is 
 asked to bear this hypothetical suggestion in mind in reading the further descrip¬ 
 tion of the boulders distributed over the surfaces of the terraces and on Coquimbo 
 Point. 
 
 At sea-level surrounding its eastern extremity La Herradura presents the smooth 
 beach of a confined water-body, and from the water a long slope rises to the foot 
 of a terrace in which there is an excavation for the railroad that connected with the 
 smelter on the northern side of the cove. On top of the terrace, east of the railroad 
 and 145 feet (44 meters) above sea, are several large erratics. They lie on the sur¬ 
 face, which consists of the horizontally bedded Pliocene shell deposits, but around each 
 of them is a slight excavation which is probably due to wind action, and it is possible 
 that they may have been undercut by the wind and may thus have sunk a little deeper 
 into the shells. They are distinctly erratic or out of place in their present setting, and 
 they are not to be assigned to the Pliocene with which they are associated. They are 
 therefore without date, but by inference may be correlated with the boulders actually 
 embedded in the strata south of the Quebrada Gulebron. The latter lie at a higher 
 level and are covered by 20 meters of additional strata. If these boulders on the plain 
 ever were so covered they have been denuded by currents of the retreating sea. It is 
 also possible that the deposits out in the bay were lacking on account of strong cur¬ 
 rents which kept the bottom scoured. In any case, the presence of large rocks such 
 as that shown in Plate LXI demand some transporting agent, such as ice, which 
 would drop them where they now lie. 
 
 It is obvious that a comparison of marine bench-marks on Coquimbo Point with 
 those which have been described by Darwin as characteristic of the eastern shore 
 
114 
 
 Earthquake Conditions in Chile 
 
 would afford opportunity for correlating the movements of the two sides of the bay 
 during the Pleistocene uplift. It is therefore of interest to note that the elevated shell 
 deposits are found on Coquimbo Point immediately above the town, and that there 
 are beach lines on the granite slopes which are marked by rows of large boulders that 
 have been carried some distance from the dikes of intrusive rock in which they 
 originated. 
 
 The limestone on Coquimbo Point appears to be identical with that on the east¬ 
 ern side of the bay. It is horizontally stratified, consists of interbedded sands and 
 hard limestone, and contains similar shells. The uppermost level is 245 feet (72 me¬ 
 ters) above sea, as determined by aneroid. The determination does not suffice for an 
 exact comparison with levels on the eastern side of the bay, since the measurement is 
 not exact and the precise stratum represented in either locality could not be identified 
 in the other. It is, nevertheless, highly probable that there is not much difference of 
 elevation, and consequently there has been no marked tilting or dislocation during the 
 uplift of the region around the bay. The shell deposits above the town are shown in 
 Plate LXII. This observation bears upon the activity on the faults, since the fault 
 which runs through the railroad yard lies between the opposite shores of the bay. 
 
 The town of Coquimbo lies crowded on the bare granite ledges of Coquimbo 
 Point to a height of about 165 feet (50 meters) above the water and scattered houses 
 occur at higher elevations. At 230 to 250 feet (70 to 75 meters) there is a marked 
 bench above which there are gentler slopes and limited areas of nearly level ground. 
 The limestone deposits described in the last paragraph occur at this elevation and 
 occupy a reentrant angle south of a dominant pinnacle of black rock. Northward 
 along the granite are strewn large black boulders, which are gathered at and just 
 below the line of the bench. The pinnacle itself is composed of similar boulders that 
 still rest in the soil formed by the subaerial decomposition of the dike. The soil is 
 lacking on the slope along which the other boulders have been carried, and they lie 
 on the bare granite (Plate LXIII). 
 
 The bench line is distinct in some profiles of the point, but is lacking in others. 
 A somewhat careful survey indicated that its development depended on conditions 
 of exposure to the waves and upon the source of material with which to form it. It 
 follows a contour so far as it can be traced. Thus it represents to all appearances an 
 elevated beach line, which has been washed away where it was sandy, but remains 
 where the cobbles and boulders were spread. It is a weakly marked line, yet appears 
 to be unequivocal in its evidence of the former level of the sea against the islet that 
 is now the point. The shell-bearing strata confirm the observation of the profiles, 
 although they lie a few meters lower, as might be expected of sediments laid down off 
 a rocky shore. It thus appears to be the fact that Coquimbo Point was submerged 
 to a level some 245 feet (75 meters) lower than that at which it now stands. 
 
 The date of the submergence is indicated by the boulders. They compare in size 
 with those seen up the Quebrada Gulebron and on the terraces above La Herradura. 
 Too large to have been carried by waves along the inner shore of the islet, they also 
 require some peculiar mode of flotation to account for their distribution. As has 
 
Geology on Coquimbo Bay 
 
 115 
 
 already been suggested, the action of shore-ice during a brief episode of unusually 
 severe climate in the earliest glacial epoch seems to afford the most probable 
 explanation. 
 
 The physical evidence which would lead to the conclusion that the maximum 
 submergence of Coquimbo Bay had been reached during the early Pleistocene, but 
 at a distinct interval after the earliest glaciation, meets with some contradiction, or 
 at least lack of confirmation, in the biologic evidence; for if the stratified marine sedi¬ 
 ments represent continuous deposition, we should expect that the warmer conditions 
 of the Pleistocene habitat would be distinguishable from the colder waters of the 
 glacial epoch and possibly from the later Pleistocene by faunal differences. So far 
 as we have the evidence this is not the case. 
 
 From his examination of the fossils which I was able to secure from several 
 localities Jordan concluded that: 
 
 “ This fauna could not have lived under conditions any more severe than the present climate 
 of Coquimbo. The conditions were probably a little warmer than at present, for not one of the living 
 forms is typical of southern Chile and most of the species belong more truly in Peru than in the 
 latitude of Coquimbo. The climatic change between the deposition of these beds and that of the 
 glacial boulders must have been great, much greater than that between the Lower and Upper San 
 Pedro beds of California and perhaps about equal to that of a change from the climate of middle 
 Lower California to that of British Columbia.” 
 
 We may accept Jordan’s conclusion as definite and final for the material which 
 he had available for examination, but I, who collected it, do not regard that material 
 as adequate and consider that the question is still open whether there may not be a 
 cold-water fauna in certain strata which would represent the colder phases of the 
 Pleistocene. To my observation, the shells above the horizon of the erratics in the 
 southern side of the Quebrada Gulebron were practically identical with those below 
 it, and we know that the earlier and later climates were certainly warm climates; but 
 I did not secure a collection from the horizon of the boulders themselves, and the few 
 fossils I did obtain from locality III, near the top of the bluff north of Gulebron, were 
 not distinctly identified when the collection was unpacked. Neither could I be sure 
 that they represented a horizon above the boulders, even if they had been recognized, 
 because the boulder zone was not found in that section and levels were not carried 
 across to its position on the south side. It is therefore possible that some more care¬ 
 ful observer and collector may yet discover a fauna indicative of colder waters, either 
 at and restricted to the boulder horizon or even occupying the strata to some height 
 above that zone. If so, it would be obvious that the fauna of the milder climate 
 retreated and returned, as that of a colder latitude advanced and retreated, while the 
 Andes assumed a glacial cap and the shores were fringed with ice, or both took on 
 semi-tropical aspects. 
 
 With reference to diastrophism, the evidence is more conclusive. The fault in 
 the railroad yard traverses limestone that has yielded a typical Miocene fossil, Ostrea 
 ingens Zittel. Movements therefore occurred during or after the Miocene and, since 
 the Paleozoic granite had been raised to near sea-level before that epoch, the faulting 
 probably began much earlier. But the apparent uniformity of level of the Pliocene 
 
 12 
 
116 
 
 Earthquake Conditions in Chile 
 
 beds east and west of the fault indicates that it had ceased to be active at least before 
 the upper strata were laid down, that is, during the Pliocene. Subsidence continued, 
 however, in the area of Coquimbo Bay, including the granite west of the fault, at 
 least to the end of the Pliocene and probably well into the Pleistocene. This area 
 then began to share in the uplift that has affected the whole Cordillera since Pliocene 
 time. The evidence of that process of elevation is found in the physiography and is 
 discussed elsewhere. 
 
REPORT ON FOSSILS FROM COQUIMBO 
 
 By Eric Jordan 
 
 INTRODUCTION 
 
 Following is a brief report on the fossils from the vicinity of Coquimbo. I have given two lists, 
 one of the species collected from each locality, the other a full list of all of the forms recognized from 
 the two formations represented. I have also given a brief discussion of the probable climatic relations 
 of the faunas. The lists are not quite complete, but I believe that little of the remaining material 
 is sufficiently well preserved to be identified with certainty. Two species believed to be new will be 
 described later. 
 
 Whether, on the basis of this collection, much can be added to the knowledge of the Coquimbo 
 formation is doubtful. However, I do not know the extent of Moericke’s paper. Most of the extinct 
 species represented in the collection were described by Philippi , 1 or by older writers. Whether or 
 not Moericke 2 discusses the climatic relations of the Coquimbo formation, I also do not know. 
 
 Species Recognized from Each Locality 
 
 Quebrada Gulebron ; bank on northeastern side near the mouth; 3 Pleistocene: 
 Pecten purpuratus Lamarck. 
 
 Marcia rufa Lamarck. 
 
 Quebrada Gulebron I and II; base of the visible Pliocene section: 
 Ostrea patagonica d’Orbigny. 
 
 Mytilus chorus Molina 
 Venus sp. 
 
 Panopea coquimboensis d’Orb. 
 
 Acanthina calcar-longum Martyn. 
 
 Chorus labialis Hupe. 
 lsevis Philippi, 
 blainvillei d’Orbigny. 
 
 Railroad cut, 0.75 Mile East of Guayacan. (Upper strata of terrace which has been scoured by marine currents, 
 that probably removed a considerable thickness down to a hard surface in the Pliocene section.—B. W.) 
 
 Glycimeris ovata Broderip 
 Pecten purpuratus Lamarck 
 Marcia rufa Lamarck 
 Chione spurca Sowerby 
 Chione cf. polydora Philippi 
 Venus sp. 
 
 Psammobia sp. 
 
 Semele solida Gray 
 Panopea guayacanensis Philippi 
 Panopea sp. 
 
 Arcularia cf. complanatus Powis 
 
 Oliva peruviana Lamarck 
 Trophon cassidiformis Blainville 
 Tritonalia crassilabrum Gray 
 Acanthina doliaris Philippi 
 Turritella cingulata Sowerby 
 Cerithiopsis sp. 
 
 Bittium sp. 
 
 Trochita trochiformis Gmelin 
 Crepidula sp. 
 
 Balanus sp. 
 
 Balanus sp. 
 
 Terrace between Coquimbo and Guayacan. Limestone in bottom of old channel. (Same as above.—B. W.) 
 Turritella cingulata Sowerby 
 Balanus sp. 
 
 Railroad Yard on Coquimbo Point. (Disturbed limestone; probably materially older.—B. W.) 
 
 Ostrea ingens Zittel 
 
 1 Tertidren und Quataren Vcrsteinerungen Chiles, Leipzig, 1887. 
 
 2 W. Moericke, Vcrsteinerungen der Tcrtidformation von Chile, Jahrbuch fur Min., Geologie, und Pal.. 
 Beilage Band 10, 1895-96, S. 548-612. 
 
 3 Superficial sediments forming the top of the bluff above an unconformity. B. W. 
 
 117 
 
118 
 
 Earthquake Conditions in Chile 
 
 Species Recognized from the Pliocene and Pleistocene of Coquimbo 
 
 ! E indicates species not known to be living] 
 
 PLEISTOCENE 
 
 
 Mouth of Quebrada Gulebron 
 
 Pecten purpuratus Lamarck 
 
 Marcia rufa Lamarck 
 
 
 £ 
 
 Quebrada Gulebron I and II; Railroad cut 0.75 mile East of Guayacan; 
 Terrace between Coquimbo and Guayacan; Railroad yard on Coquimbo 
 Point. 
 
 Glycimeris ovata Broderip 
 
 Ostrea patagonica d’Orbigny (E) 
 
 Ostrea ingens Zittel (E) 
 
 Pecten purpuratus Lamarck 
 
 Mytilus chorus Molina 
 
 Marcia rufa Lamarck 
 
 Chione spurca Sowerby 
 
 Chione cf. polydora Philippi (E) 
 
 Venus sp. 
 
 
 M 
 
 Venus sp. 
 
 
 H 
 
 Psammobia sp. 
 
 W 
 
 s 
 
 Semele solida Gray 
 
 £ 
 
 PCS 
 
 Panopea coquimboensis d’Orbigny (E) 
 
 w 
 
 u 
 
 0 
 
 Panopea guayacanensis Philippi (E) 
 
 0 
 
 
 Panopea sp. 
 
 J 
 
 M 
 
 Arcularis complanatus Powis 
 
 cu 
 
 s 
 
 Oliva peruviana Lamarck 
 
 
 1—1 
 
 Trophon cassidiformis Blainville 
 
 
 a 
 
 Tritonalia crassilabrum Gray 
 
 
 0 
 
 Acanthina calcar-longum Martyn 
 
 
 U 
 
 Acanthina doliaris Philippi (E) 
 
 
 
 Chorus labialis Hupe (E) 
 
 Chorus kevis Fhilippi (E) 
 
 Chorus blainvillei d’Orbigny (E) 
 
 Turritella cingulata Sowerby 
 
 Cerithropsis sp. 
 
 Bittium sp. 
 
 Trochita trochiformis Gmelin 
 
 Crepidula sp. 
 
 Balanus sp. 
 
 Balanus sp. 
 
 DISCUSSION 
 
 Pleistocene 
 
 The shells from the mouth of Quebrada Gulebron are undoubtedly of Pleistocene age; the 
 preservation indicates very recent deposits. As there were only two species in the lot, it is impossible 
 to determine the climatic relations of the fauna. Both are now living at Coquimbo, but it may be 
 of interest to note that both range north into the tropics, Coquimbo being practically the southern 
 limit of their range. 
 
 Pliocene 
 
 The above list includes 31 forms from the various localities around Coquimbo. Owing to the 
 rather poor condition of some of the material, in contrast to the excellent preservation of other of it, 
 full identification with any degree of certainty was in many cases impossible. Out of the list, 22 have 
 been specifically determined. Perhaps with further work one or two more might be added. 1 Of 
 these 22 recognized species, 9, or nearly one-half, are not known to be living at present. One genus, 
 Panopca, has no recent representatives on the Pacific coast of America south of California. A num¬ 
 ber of the species are present in the Pliocene Cape Fairweather 2 series of Patagonia, and a few 
 
 1 The Bittium and Cerithiopsis are undoubtedly new; they may or may not be extinct. 
 
 2 Ortmann, Princeton Expedition to Patagonia, vol. IV, Paleontojogy, part II, 1901. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXII 
 
 A. Coquimbo. Marine sediments on granite promontory west of bay, just above town, 
 
 looking south. 
 
 B. Coquimbo. Marine sediments, just above town; near view, looking into artificial cave. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXIII 
 
 A. Coquimbo. Black point above town : a mass of boulders in place in the decayed surface of 
 
 the diabase dike. 
 
 B. Coquimbo. Wave-cut bench marking high level of sea on granite islet, which is now 
 western side of bay; boulders of black diabase, moved along beach. 
 
LIBRARY 
 OF THE 
 
 UNIVERSITY Of ILLINOIS 
 
Report on Fossils from Coquimbo 
 
 119 
 
 occur in the Miocene of Patagonia. The Coquimbo formation has been described as Pliocene, 1 and 
 apparently considered as belonging to one horizon throughout. The big oyster is distinctly a Miocene 
 type, even in the Southern Hemisphere, and, although it, too, is common in the Cape Fairweather 
 formation, I believe, on the basis of this collection, that if the beds at Coquimbo are all of the same 
 horizon, they are of the middle Pliocene or older. However, with the relatively small amount of 
 material at hand it is impossible to make a definite determination. Probably Moericke was able to 
 locate the series more accurately. 
 
 As to the climatic conditions under which this assemblage lived, no definite statement can be 
 made in degrees of temperature or latitude, for the list is not long enough, and our knowledge of the 
 recent distribution of the species not sufficiently full. Nevertheless, some facts are evident as fol¬ 
 lows : (i) This fauna could not have lived under conditions any more severe than the present 
 climate of Coquimbo; (2) the conditions were probably a little warmer than the present, for not 
 one of the living forms is typical of southern Chile and most of the species belong more truly in Peru 
 than in the latitude of Coquimbo; (3) the climatic change between the deposition of these beds and 
 that of the glacial boulders must have been great—much greater than that between the Lower and 
 Upper San Pedro beds of California, and perhaps about equal to that of a change from the climate 
 of middle Lower California to that of British Columbia. 
 
 SUMMARY 
 
 It seems to me probable that these beds do not represent the top of the Pliocene, and that 
 between them and the period of floating ice there was a hiatus, perhaps considerable, represented 
 only by some obscure disconformity with no discordance in bedding. During this lost period the 
 climate changed from subtropical to distinctly cold temperate. The fauna of the cold periods may 
 well have been meager, or not represented at all in the section at Gulebron. At the close of the one or 
 two glacial periods there was, then, return to climatic conditions at least as warm as the present, 
 under which conditions the Pccten beds at the mouth of the Quebrada were deposited. 
 
 1 Presumably by W. Moericke in G. Steinnmann, Neues Jahrbuch fur Mineralogie, Geologie, und Paleon- 
 tologie, Beilige Band X, 1896. 
 
SAN FELIX AND SAN AMBROSIO 1 
 
 GENERAL DESCRIPTION AND GEOLOGY 2 
 
 San Felix and San Ambrosio are volcanic islands in the South Pacific ocean, 
 San Felix being situated in latitude 26° 15' south and longitude 8o° 7' west of Green¬ 
 wich and San Ambrosio lying about 16 km. to the east-southeast. They are about 500 
 miles (800 km.) west of Chanaral, on the coast of Chile, and the same distance due 
 north of the group of Juan Fernandez and Mas-a-fuera. The South Pacific charts 
 show several known rocks or islets and some whose existence is recorded as doubtful, 
 which, with the above-named islands, form an archipelago strewn on a narrow sub¬ 
 marine ridge that extends along the meridian of 8o° west from about 36° south to 26° 
 south, the ridge being defined by the 1,000 fathom (2,000 meter) contour line. Know¬ 
 ing that all these islands and islets are the peaks of volcanoes, we may suspect that 
 there are more of them than we can see; but this must remain an unverified guess 
 until detailed soundings can be made. The depth of the ocean in this region, which 
 lies west of the Richards Deep, varies from 2,000 to 2,500 fathoms (4,000 to 5,000 
 meters). The islands, therefore, represent the summits of volcanoes probably sixteen 
 to eighteen thousand feet or more in height—that is to say, they compare with the 
 great volcanoes of the Andes, which are situated on the other side of the deep. 
 
 San Felix and San Ambrosio are the remains of two large, distinct craters. A 
 third crater is (possibly) indicated by Peterborough Cathedral, a precipitous islet 
 about one mile northwest of San Felix. The rocks that rise above the sea are, how¬ 
 ever, little more than small remnants of the original group, and there is free play for 
 the imagination in extending the curves of the crater walls beneath the unbroken 
 expanse of sea in their vicinity. 
 
 Having sailed in May 1923 from Chanaral, the nearest port in Chile, I ap¬ 
 proached San Ambrosio from the east practically end on. It is an imposing rock, 
 rising on its southern side 850 feet (254 meters) in a sheer precipice from the surf 
 and sloping down northward to cliffs that are in general 350 feet (100 meters) high 
 along the northern shore. The width of the island is but 2,600 feet (800 meters) and 
 it is only 2 miles (3 km.) long. The chart gives its highest elevation as 1,500 feet 
 (450 meters). There is little in its somewhat oval form to suggest the curve of a 
 crater, but the obvious slope of the upper surface from south to north, and of the 
 bedded lavas of which it is formed, indicates that there was a crater south of the 
 existing fragment of the rim. On nearer approach, in circumnavigating the island, 
 a very large number of distinct lava-flows are recognizable and many vertical dikes 
 cutting through the flows can be made out. The volcanic structure is obvious. 
 
 1 Bailey Willis and H. S. Washington, San Felix and Sait Ambrosio, their Geology and Petrology, Bull. 
 G. S. A., Vol. 35 , PP- 365-384, X 9 2 4 . 
 
 2 By Bailey Willis. 
 
 120 
 
San Felix and San Ambrosio 
 
 121 
 
 It is possible to land on San Ambrosio at one point, Covadonga Cove, which is 
 nothing more than a niche in the cliffs, with just room for a moderate-sized rowboat. 
 There, in good weather, skillful seamen may effect a landing, and from that point 
 the cliffs have been climbed. The summit plateau is frequently covered with mist, 
 condensed from the air currents that ascend along the southern cliffs, and is there¬ 
 fore covered with vegetation, consisting, according to reports, of low, spreading 
 shrubs (Thaumoseris n. g. lacerata Ph.). 1 
 
 I did not myself land on San Ambrosio and am indebted to Captain Stuart D. 
 Campbell for a specimen of the lava taken from the foot of the cliffs at Covadonga 
 Cove. 
 
 The island of San Felix, unlike San Ambrosio, is a low platform, forming a 
 crescent and ending in two rounded hills. At the northwest extremity the so-called 
 Cerro Amarillo is 600 feet (183 meters) high and of a deep yellow color, due to the 
 decomposition of the basic tuff of which it is composed. At the other, the south¬ 
 eastern extremity, is a similar hill of the same material, 435 feet (132 meters) high, 
 which is known as Islota Gonzales. It is separated from the main island by a breach, 
 where the breakers roll over the scarcely submerged rocks. The intervening plat¬ 
 form, which stretches between Cerro Amarillo and Islota Gonzales, has an altitude 
 of 200 to 250 feet (60 to 70 meters) in the cliffs along the southern, inner, side of the 
 crescent and of 50 to 65 feet (15 to 20 meters) along the northern coast. The total 
 length of the curving island and islet between the extremities is about 3 miles (5 km.), 
 and that of the island of San Felix is but 2 miles (3 km.). The width of San Felix 
 varies from 1,600 to 3,300 feet (500 to 1,000 meters). 
 
 In approaching San Felix from San Ambrosio—that is, from the southeast— 
 one is struck by the difference in form between the rounded hills at the extremities 
 and the flat table between them. The difference in color is also notable, the hills being 
 bright yellow, whereas the table is jet black. On closer examination it is apparent 
 that the yellow tuff is the older and the black lava is the younger of the two. 
 
 It seems worth while here to introduce the story of a change of opinion that was 
 forced on me by the actual relations of the rocks as contrasted with those which 
 seemed to be apparent, in the view from a distance. I approached San Felix with 
 certain preconceptions connected with the earthquake of November 10, 1922, and 
 suggested by the accounts of the island given me by Captain Campbell, who had 
 visited it in October 1922, and again in February 1923. I11 the latter visit the after¬ 
 shocks of the great earthquake were frequent and severe during the four days the 
 Captain spent in the vicinity of the island and on it. He was overcome by volcanic 
 gases on ascending to the platform with the intention of climbing Cerro Amarillo, 
 and he had become convinced that the volcano was an active center in which the 
 earthquake had originated. His account was very circumstantial and so fitted in with 
 general facts of volcanic phenomena that I expected to find evidences of recent 
 eruption. 
 
 1 Report of an exploration of the islands of San Felix and San Ambrosio by the frigate Covadonga, Don 
 Ramon Vidal Gormaz, captain, 1875. 
 
122 
 
 Earthquake Conditions tn Chtle 
 
 In approaching the island, we sailed around the southern side with a leeway of 
 about a mile from the two extremities of the crescent, and we could clearly see the 
 surf dashing high on the cliffs of the black platform. Captain Campbell had told me 
 that he and his sailors had seen a dull red glow on the summit of Cerro Amarillo, 
 when anchored some eight or ten miles distant. I therefore examined the peak for 
 evidences of eruption. The top was cup-shaped and within it lay a mass of black lava 
 from which small streams had run down the cliffs to the sea. No one who examined 
 it from that distance could reasonably doubt that it was a very recent, though small, 
 local eruption. It might even still be hot. 
 
 On the following day, with several officers of the naval vessel which the Chilean 
 Government had courteously put at my service for the trip, I climbed Cerro Amarillo, 
 keeping well to windward of possible gas emanations. My chagrin may be imagined 
 when I found small bushes growing on the supposed hot lava, and was forced by a 
 study of its relations to recognize it as a splash from the old crater which had been 
 thrown up on the yellow tuff and had run back into the crater at the time of the erup¬ 
 tion of the black table lava. 
 
 It had been reported in perfect good faith that San Felix was shaken by the earth¬ 
 quake, and that its eastern end was broken off and had sunk beneath the sea, and 
 that it was the center of violent convulsions. It shows cracks attributable to the earth¬ 
 quake, but the rest of the statement is as much the work of imagination as was the 
 recent eruption of which I thought that I saw evidences. The island is volcanic and 
 it is probably not many centuries since the eruption of the black lava. Volcanic gases 
 were still issuing from a crevice in the southern rim in May 1923, and they were 
 reported by Captain Campbell and by the sailors who accompanied him in February 
 as having been sufficient in volume to overcome him. 
 
 The bird life of the island, which many visitors have described as exceedingly 
 abundant, had either been destroyed or driven away. I counted twenty-five live birds 
 and fifty dead ones on the entire island, where formerly there must have been many 
 thousands. It is probable that most of those that were killed were eaten by other 
 birds and by insects, and that their light bones and feathers were blown from the 
 unprotected rocks into the sea. The large colony of lobsters which lived on the reefs 
 around the island and which formed an attraction that drew fishermen like Captain 
 Campbell to it had been destroyed, leaving but few survivors. A Spanish diver, 
 Mauricio Pardesano, who was with Captain Campbell on his two fishing expeditions 
 and who also accompanied me, stated that the sea-floor was covered with the cara¬ 
 paces of dead lobsters. Captain Campbell and Pardesano independently stated that 
 during their visit in February the ocean water was tepid, distinctly warm. They said 
 that it was warmer immediately succeeding each one of the repeated earthquake 
 shocks, and Pardesano found it much warmer on the bottom than at the surface. 
 
 These facts all point to considerable emanations of gas at the time of the great 
 earthquake and during the succeeding months. In May, as already stated, some gas 
 was still issuing from a crevice along the southern cliffs of the island, as was shown 
 

 
 
 
 
 
 
 
 
 
Plate LXIV 
 
 Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 A. San Ambrosio. Near view of southwest cliff, showing bedded lavas and vertical dikes. 
 
 B. San Ambrosio. From the west in silhouette against the morning sun, 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXV 
 
 A. 
 
 Isla San Felix. 
 
 Looking east over anchorage to basalt pinnacles known as the Catedral 
 de Peterborough. 
 
 B. San Ambrosio. From the southeast. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXVI 
 
 A. Jsla San Felix. Cerro Amarillo, the hill of yellow tuff, as seen from black lava flow looking 
 
 north; height of Cerro 660 feet (200 meters). 
 
 I>. fsla San Felix. Western base of Cerro Amarillo, sloping into crater showing structure of tuff. 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXVII 
 
 A. Jsla Sau Felix. Cave at junction of younger black lava flow with older tuff of Cerro Amarillo. 
 
 B. Isla San Felix. Looking south from Cerro Amarillo over recent black lava flow; Isla San 
 
 Ambrosio in distance; Isla Gonzales on right. 
 

Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 A. Isla San Felix. View of island, looking south from ship at anchor. 
 
 On 
 
 right is Cerro Amarillo, 660 feet 1b 
 a large cave. Only feasible landing I 
 
Plate LXVIII 
 
 fe, toward left stretches plateau of recent basalt flows; at contact of basalt with tuff hill the waves have eroded 
 Ian wave-cut shelf at right of cave. 
 
 erescent, which terminates in island at right, surrounds about two-fifths of crater. In distance is seen the 
 inrosio. 
 

 
 
 
 
 
 
 
 
 
 
San Felix and San Ambrosio 
 
 123 
 
 by the sulphurous smell and puffs of blue vapor observed by me and by the Chilean 
 officers. In this sense and to this extent we may consider San Felix an active volcano. 
 
 The date of the latest eruption, that of the black lava, is a matter of considerable 
 interest, but we are forced to set it prior to the discovery of .the island, in 1574, be¬ 
 cause there seems to have been no change in the general configuration of the group 
 since Tuan Fernandez first discovered it. Were this fact not unquestionable, one 
 would not suppose the black lava to be 350 years old or more. Its surface still shows 
 the distinct forms of pahoehoe, the glistening surfaces and the ropy eddies of recently 
 cooled slag. One is not surprised that there is no soil, for the winds blow everything 
 but coarse sand from the rocks, but as one walks over the irregular surface of the 
 old flow it is very difficult to believe that it is actually as old as it must be. When, 
 however, I ascended to the cliffs of the southern side and looked from them over the 
 site of the old crater from which the lava must have flowed, it was less difficult to 
 realize its antiquity. At least three-fifths of the crater wall is gone and the ocean 
 rolls over its foundations. The southern crater wall must have existed and have stood 
 at a height greater than that of the remaining remnant or the lava would not have 
 poured out where it did. Whether the missing part was blown up, or melted down, or 
 faulted off, one may guess according to one’s inclinations; there is no evidence one 
 way or the other. 
 
 Not only is the crater wall of greater San Felix lost beneath the ocean, but an 
 even larger part of the old crater of San Ambrosio is gone and the Cathedral of 
 Peterborough is a central remnant, a volcanic neck of a third lost crater. 1 
 
 The Cathedral of Peterborough is a very striking rock, a group of columns rising 
 about 175 feet (50 meters) above the sea, pierced through by the waves and sur¬ 
 rounded by reefs that seem to represent other columns that have fallen. It is practi¬ 
 cally inaccessible, but its dense, black, jointed, columnar masses leave little doubt that 
 it is a basaltic, volcanic neck. 
 
 I spent two half-days on San Felix and recognized three distinct types of rock 
 of as many different periods of eruption. The youngest is the black lava which forms 
 the platform of the island. It very distinctly overlies and is splashed up on the yellow 
 tuff, both at Cerro Amarillo and at Islota Gonzales. The contact is easily observed at 
 the landing place, where a cavern has been worked out of the rock. In the adjacent 
 cliffs one may count fifteen or more distinct layers (flows), all of the same dense, 
 black, vesicular lava, which is so uniform in appearance from end to end of the island 
 that I was convinced that it was all of one and the same eruption. I was, therefore, 
 satisfied to collect specimens from one locality only, namely, from the upper 10 or 15 
 feet (3 or 4 14 meters) of the black cliff immediately above the landing, and I would 
 suppose that any differences in the chemical composition, such as have been found in 
 the specimens, may be explained as differences in the somewhat considerable volume 
 of the magma. 
 
 1 It seems to be possible, judging from the soundings given on the chart and from its columnar structure, 
 that Peterborough is a parasitic cone of San Felix or more probably the end of a massive flow from this crater.— 
 H. S. W. 
 
124 
 
 Earthquake Conditions in Chile 
 
 The next older lava is the yellow tuff which forms the Cerro Amarillo and the 
 peak of Islota Gonzales. In Cerro Amarillo the structure is that of concentric layers, 
 which strongly suggest those that are seen on a smaller scale in the cone that forms 
 around a small orifice in larger craters. The layers are steeply inclined and concen¬ 
 tric to the cone, on the north side all around from east to west; on the southern side 
 they are less complete. I do not feel sure, however, that these are original structures. 
 The rock is greatly decomposed and the bedded structure might be due to chemical 
 reaction and increase of volume. The latter suggestion is strengthened by the fact 
 that they are very thin, but a few inches to a foot in thickness, and there seems to 
 have been no crater from which the tuffs could have been extruded to form an indi¬ 
 vidual cone. If, as seems most probable, the yellow tuff of Islota Gonzales is identical 
 with that of Cerro Amarillo, they were both erupted from the intervening crater, 
 and the conical structure of Cerro Amarillo would be secondary rather than original. 
 
 The third type of rock on San Felix is a light gray trachyte, which exhibits a 
 very thinly laminated structure and strikingly suggests a schist. It occurs in frag¬ 
 ments up to a foot in diameter in the yellow tuff of Cerro Amarillo and was obviously 
 torn off from some deeper mass and brought up with the tuff. The schistose struc¬ 
 ture is so striking that I did not suspect the volcanic nature of the rock and framed 
 some entertaining hypotheses of a continental platform or submarine fault. 
 
 The trip to San Felix was undertaken in connection with the great earthquake 
 that shook northern Chile on the tenth of November, 1922. The immediate incentive 
 was found in the reports of Captain Campbell, who on his return from the islands 
 in February wrote me regarding his experiences. The basic facts were as he saw 
 them, so far as I was able to judge, even though his fancy suggested inferences that 
 proved to be exaggerated. It seems evident that the earthquake shook not only Chile, 
 but also the other side of the great deep, 500 miles (800 km.) off the coast. It also 
 broke cables at a depth of 1,200 fathoms (600 meters) in the intervening depression, 
 and it shook down buildings in mining towns 100 miles (160 km.) east of the coast; 
 that is to say, the width of the zone of recognized activity is 600 miles (1,000 km.). 
 From south to north the earthquake was distinctly felt through twenty degrees of 
 latitude, from Concepcion to Iquique, approximately 1,400 miles (2,250 km.). In 
 other words, it was so extensive that it could not be attributed to any local center of 
 activity, such as a volcano, but may rather be classed as a regional phenomenon 
 expressed in the elastic vibration of an enormous mass of rock underlying the great 
 deep off the Chilean coast. 
 
San Felix and San Ambrosio 
 
 125 
 
 PETROLOGY OF SAN FELIX 1 
 General Statement 
 
 The specimens entrusted to me by Professor Willis for study represent the three 
 kinds of rock that were observed by him to occur on San Felix. It would appear, from 
 the few chemical analyses that I have made, that the trachytes are rather uniform in 
 general composition, whereas the later flows of basalt that make up the midway pla¬ 
 teau differ somewhat more widely in their characters; so that further collections 
 from different points on the island, especially from the latest splash of lava that has 
 been described by Willis, and from the upper and the lower flows, would be very desir¬ 
 able. The analysis of a specimen of lava from San Ambrosio that was given to 
 Professor Willis by Captain Campbell is described separately at the close of this 
 paper. 
 
 Trachyte 
 
 There are two varieties of the trachyte that occur as blocks in the yellow tuff 
 of Cerro Amarillo; one is very schistose and typically holocrystalline, the other is 
 massive and decidedly vitreous. The two types appear to differ slightly in chemical 
 composition, but less so in their mineral characters. 
 
 The variety of trachyte that seems, from the description by Willis and from the 
 specimens collected by him, 2 to be the more abundant is medium gray, densely com¬ 
 pact, aphanitic and aphyric; none of the specimens is vesicular. The rock is mark¬ 
 edly, but variably, schistose. Some of the specimens split readily into thin, fairly 
 smooth plates, whereas in others this character is less pronounced, but is still evident. 
 The schistosity of most of the specimens is so prominent that both of the authors were 
 led, on a first inspection, to think that the rock was a metamorphic schist. 
 
 In thin section the rock shows a somewhat peculiar trachytic texture, which 
 resembles that of the trachyte of Mas-a-fuera described by Quensel, 3 that of Puu 
 Anahulu on the Island of Hawaii, 4 and of the trachyte of Lahaina on Maui. 5 The 
 texture seems to be rather usual in the trachytes of the Intro-Pacific volcanic islands. 
 Ill-defined laths of alkali feldspar make up most of the rock. For the most part these 
 are arranged irregularly, but here and there flow texture is evident. A considerable 
 number of the feldspar laths are somewhat shorter and thicker; these are uniformly 
 dull and cloudy, as if from kaolinization, although the very small amount of water 
 shown in the analysis is opposed to this explanation. But they are of different chemi¬ 
 cal composition from the longer, thinner, clearer and more numerous laths, whose 
 optical characters indicate that they are more sodic. Many very small prismoids of 
 colorless pyroxene, which is presumably acmite, almost without diopside, judging 
 
 1 By H. S. Washington. 
 
 2 There are four specimens of this variety and one of the other. 
 
 3 P. D. Quensel, Die Geologic der Fcrnandesinseln, Bull. Geol. Inst. Upsala, xxx, vol. n, 1912, p. 283. 
 
 4 Whitman Cross, An Occurrence of Trachyte on the Island of Hawaii, Jour. Geol., vol. 12, 1904, p. 510; 
 and Lavas of Hawaii and their Relations, U. S. Geol. Surv. Prof. Paper 88, 1915, p. 35. H. S. Washington, 
 Petrology of the Hawaiian Islands: II, Hualalai and Mauna Loa, Am. Jour. Sci., vol. 6, 1923, p. 106. 
 
 5 Whitman Cross, Lavas of Hawaii and their Relations, U. S. Geol. Surv. Prof. Paper 88 , 1915, P- 26. 
 
126 
 
 Earthquake Conditions in Chile 
 
 from the chemical analysis, and minute grains of magnetite are scattered through 
 the rock. A scanty, colorless, isotropic or feebly birefringent base is probably the 
 nephelite that is shown in the norm. 
 
 An analysis of a moderately schistose specimen is given in No. i of the accom¬ 
 panying table. It is that of a dominantly sodic trachyte, such as is associated with 
 highly sodic, nephelite-bearing rocks in many well-known comagmatic regions. The 
 high alkalies and the high ratio of ferric oxide to ferrous, the latter characteristic of 
 holocrystalline as opposed to hyaline lavas, are the most notable features, and the 
 rather high zirconia is a minor feature of some interest. The norm (table III, No. I) 
 shows a small amount of diopsidic acmite and of nephelite. The average feldspar is 
 a decidedly sodic orthoclase. It is probable, as has been remarked, that the stout 
 cloudy feldspars are of potassic orthoclase, whereas the more numerous clear, thin, 
 and longer tables are of a more sodic anorthoclase than the average. 
 
 The great similarity between this trachyte and those of other Intro-Pacific 
 islands is shown by the analyses of such lavas that are cited in Table I for compari¬ 
 son. They will be discussed later. 
 
 H yalo-T rach yte 
 
 One of the specimens of trachyte from Cerro Amarillo is of a type rather differ¬ 
 ent from that just described. This rock is much darker gray, and it shows many 
 minute glistening faces of feldspar in a dense, very dark gray, aphanitic groundmass, 
 which has the subresinous luster characteristic of many vitreous lavas. There is only 
 a very slight tendency to schistosity in this specimen; the fracture is generally even, 
 but parallel to one plane the fracture surface is slightly wavy, made up of narrow, 
 parallel, low, rounded ridges, like a slightly crumpled schist. 
 
 The thin-section shows some small phenocrysts of orthoclase, as sharply defined, 
 well-shaped, thick tables, many of which are twined according to the Carlsbad law. 
 These appear to be of orthoclase that contains little or no soda, which was the first 
 mineral to crystallize. There are present also rather more numerous, less well- 
 bounded, thinner and longer tables of a more sodic feldspar. These feldspars lie, with 
 marked flow texture, in a base of light-brown glass, which itself shows flow texture in 
 streaks of slightly darker material. Very few, minute crystals of olivine are present, 
 which for the most part are seen clearly only under high powers. Grains of mag¬ 
 netite are very rare and no pyroxene is present. 
 
 The chemical composition of this trachyte (No. 2, Table I) differs from that of 
 the schistose type chiefly in the lower silica and soda, the higher ferrous oxide, and 
 the slightly higher magnesia and lime, although these differences change the position 
 of the rock in the quantitative classification only in the subrang. Phosphorus pen- 
 toxide is rather high, a feature that seems to be characteristic of many of the lavas 
 of the Intro-Pacific volcanoes. The norm (Table III) shows the presence of a little 
 nephelite but no pyroxene. There appear to occur in the Pacific fewer analogues of 
 this type of trachyte than of the other. 
 
San Felix and San Ambrosio 
 
 127 
 
 Table I —Analyses of trachytes 
 
 1 
 
 I 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 SiO, . 
 
 62.54 
 
 58.22 
 
 6343 
 
 62.02 
 
 61.90 
 
 58.84 
 
 1 A1203 . 
 
 18.33 
 
 18.31 
 
 18.64 
 
 18.71 
 
 18.37 
 
 20.30 
 
 FeiOa . 
 
 2.11 
 
 2.63 
 
 2.78 
 
 4-30 
 
 2.46 
 
 2.74 
 
 FeO . 
 
 0.82 
 
 1.91 
 
 1.02 
 
 0.10 
 
 0.66 
 
 0.64 
 
 MgO . 
 
 0-33 
 
 0.97 
 
 1.38 
 
 0.40 
 
 0.46 
 
 0.60 
 
 CaO . 
 
 0.92 
 
 1.52 
 
 1.68 
 
 0.86 
 
 0.58 
 
 1.66 
 
 Na 2 0 . 
 
 8.02 
 
 6.14 
 
 6-77 
 
 6.90 
 
 7-95 
 
 748 
 
 K 2 0 . 
 
 5-70 
 
 578 
 
 3.82 
 
 ,4-93 
 
 5-36 
 
 572 
 
 H2O -f- . 
 
 0.15 
 
 14 7 \ 
 
 
 / 0.80 
 
 i-52 
 
 0.68 
 
 H2O — . 
 
 0.05 
 
 0.86/ 
 
 0.24 
 
 I0.31 
 
 0.61 
 
 0.31 
 
 CO2 . 
 
 none 
 
 none 
 
 n. d. 
 
 none 
 
 n. d. 
 
 n. d. 
 
 TiOa . 
 
 1.24 
 
 0.92 
 
 0.28 
 
 0.31 
 
 0.20 
 
 0.72 
 
 Zr0 2 . 
 
 0.12 
 
 n d. 
 
 n. d. 
 
 0.06 
 
 n. d. 
 
 n. d. 
 
 P2O5 . 
 
 0.13 
 
 0.90 
 
 0.18 
 
 0.24 
 
 0.01 
 
 0.13 
 
 Cl . 
 
 n. d. 
 
 n. d. 
 
 0.04 
 
 none 
 
 n. d. 
 
 n. d. 
 
 s.. 
 
 0.03 
 
 n. d. 
 
 O.OI 
 
 0.02 
 
 n. d. 
 
 n. d. 
 
 O20.1 . 
 
 none 
 
 n. d. 
 
 n. d. 
 
 none 
 
 trace 
 
 0.02 
 
 MnO . 
 
 0.15 
 
 0.16 
 
 0.09 
 
 0.15 
 
 0.26 
 
 0.12 
 
 BaO . 
 
 none 
 
 n. d. 
 
 n. d. 
 
 0.02 
 
 n. d. 
 
 0.07 
 
 
 100.64 
 
 9979 
 
 100.36 
 
 100.13 
 
 1 
 
 100.34 
 
 100.03 
 
 1. Schistose trachyte, blocks in tuff, Cerro Amarillo, San Felix. H. S. Washington, analyst. 
 
 2. Hyalo-trachyte, blocks in tuff, Cerro Amarillo, San Felix. H. S. Washington, analyst. 
 
 3. Trachyte, Mas-a-fuera, Juan Fernandez Islands. Sahlbom, analyst. P. Quensel, Bulletin of the Geological 
 Institute of Upsala, volume 11, 1912, page 283. 
 
 4- Trachyte, Puu Anahulu, Hualalai, Hawaii. Washington, analyst. H. S. Washington, American Journal 
 of Science, volume 6, 1923, page 108. 
 
 5. Nephelite trachyte, Mauratapu, Huahine, Society Islands. Morley, analyst. Iddings and Morley, Pro¬ 
 ceedings of the National Academy of Sciences, volume 4, 1918, page 114. 
 
 6. Phonolite, Vaitia, Taiarapu, Society Islands. Morley, analyst. Iddings and Morley, op. cit., page 114. 
 
 Nephelite Basanite 
 
 The “ basalts ” of the low middle portion of San Felix appear megascopically 
 to be quite uniform, but the specimens collected by Willis show, chemically, consid¬ 
 erable variation. They are all dense, black, mostly aphanitic and almost aphyric lavas. 
 Most of the specimens are of typical pahoehoe, fresh and with the characteristic 
 corded surfaces and finely uniform vesiculation of this form of lava. These have 
 rather sparse, very small phenocrysts of dark-green olivine scattered through a dense, 
 aphanitic, slightly brownish-black groundmass, which has a subresinous luster. One 
 specimen comes from what appears to be a flow of aa lava; at least the vesiculation 
 is of the kind with few irregularly shaped and rather large vesicles. This is very dark 
 gray, not the jet black of the pahoehoe specimens, and contains some small phenocrysts 
 of yellow olivine in a dense aphanitic groundmass that has a dull stony luster without 
 any resinous quality. 
 
 The thin-sections of all these basalts are very unsatisfactory for study, because, 
 even if very thin, they are so black, dense and opaque that very little of their texture 
 or mode is visible. Both types show some small (up to i mm.), well-formed phe¬ 
 nocrysts of fresh olivine, which is entirely free from inclusions. There are no phe¬ 
 nocrysts of feldspar, pyroxene or other minerals. The groundmass in the pahoehoe 
 specimens is black and almost perfectly opaque, the thin edges alone showing slight 
 indications of the presence of extremely minute feldspar needles and small prismoids 
 
 13 
 
128 
 
 Earthquake Conditions in Chile 
 
 of pyroxene embedded in a brown dusty glass. These are seen rather better in the 
 specimen of aa, which is slightly more crystalline than the pahoehoe, but the feldspar 
 needles are too minute for satisfactory identification of the kind of plagioclase. No 
 trace of flow texture is visible in any of the thin-sections. 
 
 Table II — Analyses of nephelite basanite and basalt 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 SiO, . 
 
 46.22 
 
 43.20 
 
 43-47 
 
 43-37 
 
 46.43 
 
 44-74 
 
 4376 
 
 AhOa . 
 
 12.29 
 
 8.51 
 
 17.30 
 
 8.48 
 
 10.91 
 
 16.74 
 
 11.58 
 
 FejOn . 
 
 2.14 
 
 3-49 
 
 6.87 
 
 2.91 
 
 3.15 
 
 3-70 
 
 4-39 
 
 FeO . 
 
 7.91 
 
 7.84 
 
 7.09 
 
 11.00 
 
 10.26 
 
 8-53 
 
 7-57 
 
 MgO . 
 
 7-55 
 
 12.04 
 
 8.60 
 
 25-93 
 
 11.08 
 
 4.80 
 
 12.97 
 
 CaO . 
 
 8.94 
 
 10.21 
 
 6.09 
 
 5-03 
 
 10.09 
 
 9.88 
 
 9.64 
 
 Na 2 0 . 
 
 4.04 
 
 5-07 
 
 2.53 
 
 1-33 
 
 3.16 
 
 4.42 
 
 3-03 
 
 KaO . 
 
 3-33 
 
 0.69 
 
 0.74 
 
 0.58 
 
 0.54 
 
 1.14 
 
 1.84 
 
 H 2 0 + . 
 
 H2O — . 
 
 0.08 
 
 0.04 
 
 5.86 
 
 0.78 J 
 0.71 J 
 6.78 
 
 3-46 
 
 | 0.19 
 
 0.66 
 
 0.15 
 
 2-59 
 
 1 . 12 
 0.33 
 3-68 
 
 0.47 
 
 Tib* . 
 
 2.68 
 
 1.03 
 
 3-41 
 
 Zr 0 2 . 
 
 0.02 
 
 n. d. 
 
 n. d. 
 
 n. d. 
 
 none 
 
 n. d. 
 
 n. d. 
 
 P 3 0 6 . 
 
 1.12 
 
 0.58 
 n. d. 
 
 0.27 
 
 0.18 
 
 0.19 
 
 0.08 
 
 0.67 
 n. d. 
 
 0.70 
 n. d. 
 
 045 
 
 n. d. 
 
 ci . 
 
 n. d. 
 
 s . 
 
 0.02 
 
 n. d. 
 
 0.12 
 
 trace 
 
 0.07 
 
 n. d. 
 
 n. d. 
 
 Cr a 0 3 . 
 
 0.05 
 
 n. d. 
 
 n. d. 
 
 n. d. 
 
 none 
 
 trace 
 
 n. d. 
 
 MnO . 
 
 0.17 
 
 0.15 
 
 0.07 
 
 9-13 
 
 0.09 
 
 0.19 
 
 n. d. 
 
 BaO . 
 
 none 
 
 
 n. d. 
 
 n. d. 
 
 none 
 
 n. d. 
 
 n. d. 
 
 
 
 
 99.78 
 
 100.05 
 
 99.60 
 
 100.25 
 
 99-85 
 
 99-97 
 
 99.72 
 
 1. Nephelite basanite (pahoehoe), San Felix. Washington, analyst. 
 
 2. Nephelite basanite (aa), San Felix. Washington, analyst. 
 
 3. Nephelite basanite, Mas-a-fuera, Juan Fernandez Islands. Sahlbom, analyst. Quensel, op. cit., page 280. 
 
 4. Picrite basalt, Mas-a-fuera. Sahlbom, analyst. Quensel, op. cit., page 287. 
 
 5. Olivine basalt, lava of 1801, Hualalai, Hawaii. Washington, analyst. American Journal of Science, 
 volume 6, page 102. 
 
 6. Nephelite basalt, Tapahi, Tahiti, Society Islands. Foote, analyst. Iddings and Morley, Proceedings of 
 the National Academy of Sciences, volume 4, 1918, page 115. 
 
 7. (Nephelite) basalt, Matavanu Volcano, Savaii, Samoan Islands. Heussler, analyst. Klautsch, Jahrb. 
 Preuss. Geol. L.-Anst., volume 27, 1910, page 174. 
 
 Table III — Norms of San Felix rocks 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 Or . 
 
 33-92 
 
 34-47 
 
 19.46 
 
 3-89 
 
 Ab . 
 
 49-51 
 
 48.99 
 
 14.67 
 
 12.05 
 
 An . 
 
 
 1-95 
 
 5.84 
 
 
 Ne . 
 
 6.96 
 
 1.56 
 
 10.51 
 
 15-05 
 
 C . 
 
 
 1.22 
 
 
 
 Ac . 
 
 4-63 
 
 
 
 2.77 
 
 Di . 
 
 1.72 
 
 
 24.61 
 
 36.66 
 
 01 . 
 
 1.68 
 
 7.52 
 
 10.10 
 
 Mt . 
 
 
 3-71 
 
 3.02 
 
 371 
 
 11. 
 
 2.28 
 
 1.82 
 
 n.25 
 
 12.92 
 
 Hm . 
 
 0.48 
 
 . 
 
 
 
 Ap . 
 
 0-34 
 
 2.02 
 
 2.69 
 
 1-34 
 
 1. Schistose trachyte, No. 1, Table I, I(II).5".1."4. 
 
 2. Hyalo-trachyte, No. 2, Table I, I(II).5.1.3(4). 
 
 3. Nephelite basanite, No. 1, Table II, III.6."2.(3)4 
 
 4. Nephelite basanite, No. 2, Table II, IV.2.2.2".2. 
 
San Felix and San Ambrosio 
 
 129 
 
 Two analyses were made of these “ basalts,” one of a very fresh, corded pahoehoe 
 (Table IT, No. i), the other of the specimen of aa (Table II, No. 2). Although they 
 resemble each other in their most general features, there is considerable difference 
 between them. The low silica and alumina and the high soda show that they are not 
 analyses of ordinary basalts, and the norms (Table III) indicate that much nephe- 
 lite would have been present had they been fully crystallized. The norms indicate 
 also that the feldspar is, in general, oligoclase or even more alkalic, and the norm of 
 No. 2 shows a small amount of acmite, indicating an excess of soda. The presence 
 of such highly sodic feldspar in rocks that are so femic is somewhat unusual. The 
 percentage of titanium dioxide is very high in both rocks, as is also that of phos¬ 
 phorus. The former feature appears to be general among the more femic lavas of 
 the Pacific, while high phosphorus is common in the more feldspathic ones. 
 
 Tuff 
 
 The tuff that makes up Cerro Amarillo, and presumably Islota Gonzales also, is 
 dense, compact and very coherent, breaking with an uneven fracture. It can be read¬ 
 ily scratched, but not cut, with a knife-blade. Its color is a rather deep yellow-orange, 
 about the “ cinnamon ” of Ridgway (15") ; the luster is dull and earthy. Throughout 
 the mass are scattered many small (from 1 mm. to 1 cm.), usually rounded frag¬ 
 ments of a jet-black substance, with a vitreous luster, which study of the thin-section 
 shows to be a basaltic glass. None of the specimens brought back by Willis shows 
 the platv parting noted by him in the mass. 
 
 The thin-sections show that the tuff is composed for the most part of a bright 
 orange-yellow, opaque or subtranslucent, indefinite substance, partly in somewhat 
 rounded or irregular areas, with narrow veinlets of calcite between them here and 
 there. Small crystal fragments of olivine are not very numerous; there are rare 
 small black grains of magnetite, but no definite crystals of either feldspar or pyroxene 
 are present. The black basaltic inclusions consist very largely of a light yellowish- 
 brown glass, in which are scattered many sharply formed crystals and fragments 
 of colorless olivine, which contains few very minute grains of magnetite. In the 
 thinner parts of the glass base can be seen, somewhat vaguely, very small thin prisms 
 of a colorless, transparent mineral, with oblique extinction, which is considered to be 
 pyroxene. No crystals of feldspar could be definitely made out. The glass is finely 
 vesicular, with many small rounded vesicles, some of which are filled with secondary 
 calcite. The basalt resembles the very glassy nephelite basanites already described, 
 except that the glass base of the fragments in the tuff is much lighter brown and far 
 more transparent, without the abundant black dust of the flow material and with 
 minute microphenocrysts of pyroxene rather than of feldspar in the glass base. An 
 analysis of these fragments would be of interest. The contacts between the basaltic 
 fragments and the yellow tuff base are sharp. The yellow tuff is probably a lithic, 
 devitrified and somewhat decomposed tuff 1 of the glassy basalt of the fragments, 
 which approaches the nephelite basanites in composition. 
 
130 
 
 Earthquake Conditions in Chile 
 
 An analysis was made of a typical specimen of the yellow tuff, the results of 
 which are given in Table IV, No. i, with some of the very few usable analyses of 
 basaltic tuffs that are to be found in the literature. The analysis is notable chiefly 
 for the high alkalies, in which respect (as well as in the low alumina) it is in marked 
 contrast with the other analyses, which are of basaltic tuffs. The high titanium diox¬ 
 ide and phosphorus pentoxide may also be mentioned. These three features, as we 
 have seen, are characteristic of the analyses of the black, highly vitreous, nephelite 
 basanites that make up the flows of San Felix. This correspondence in certain chemi¬ 
 cal features gives additional weight to the supposition, already suggested by the pres¬ 
 ence of the fragments of brown hyalo-basalt, that the yellow tuffs of San Felix are 
 derived from nephelite basanite; they are certainly not derived from ordinary basalts, 
 as the analyses in Table IV render evident. 
 
 Table IV— Analyses of tuffs 
 
 I 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 SiO; . 36.35 
 
 39.00 
 
 4743 
 
 34-39 
 
 37-82 
 
 43-48 
 
 45-18 
 
 AkO, . 8.14 
 
 15-58 
 
 17.20 
 
 13-05 
 
 13-16 
 
 9-74 
 
 10.55 
 
 Fe 2 0 3 . 5-57 
 
 6.13 
 
 4.20 
 
 5.20 
 
 14.11 
 
 6.66 
 
 2.85 
 
 FeO . 3-50 
 
 3-11 
 
 5-2 7 
 
 0.98 
 
 0.14 
 
 4.19 
 
 7.90 
 
 MgO . 9-05 
 
 6.55 
 
 4-85 
 
 8.62 
 
 H -75 
 
 10.83 
 
 9.90 
 
 CaO . 744 
 
 6.82 
 
 7-56 
 
 18.52 
 
 13-39 
 
 8.90 
 
 9.68 
 
 t Na 2 0 . 4-70 
 
 3.22 
 
 3-53 
 
 2.56 
 
 1.66 
 
 5.62 
 
 4.61 
 
 K 2 0 . 3-25 
 
 0-59 
 
 1.51 
 
 0.24 
 
 1.49 
 
 3-89 
 
 2.03 
 
 H >0 + . 4.01 
 
 6.03 
 
 2.42 
 
 3.72 
 
 
 
 
 H ,0 . 8.33 
 
 8.18 
 
 3.T2 
 
 2.22 
 
 
 
 
 1 CO- . 4.00 
 
 1.83 
 
 none 
 
 10.89 
 
 5.56 
 
 
 
 T iO.. 4-76 
 
 2-59 
 
 3.00 
 
 0.63 
 
 n. d. 
 
 5-70 
 
 6.38 
 
 P 2 0 5 . 0.83 
 
 n. d. 
 
 n. d. 
 
 n.d. 
 
 0.82 
 
 0-99 
 
 0.86 
 
 MnO . n. d. 
 
 n. d. 
 
 n.d. 
 
 n. d. 
 
 0.24 
 
 
 
 
 
 
 
 
 
 99-95 
 
 99.63 
 
 100.09 
 
 101.09 
 
 100.41 
 
 100.00 
 
 100.00 
 
 1. Yellow basanite tuff, Cerro Amarillo, San Felix Island. Washington, analyst. 
 
 2. Yellow basalt tuff, Monte Pozzolana, Linosa Island. Washington, analyst. Journal of Geology, volume 16, 
 1908, page 29. 
 
 3. Gray basalt tuff, Monte Levante, Linosa Island. Washington, analyst. Loc. cit. 
 
 4. Basalt tuff, Copper Island, Commander Islands, Bering Sea. Staronka, analyst. Morozewicz, Com. C. 
 Russ., Mem. 72, 1913, page 73. 
 
 5. Basalt tuff, Punch Bowl, Oahu, Hawaiian Islands. Lyons, analyst. American Journal of Science, 
 volume 2, 1896, page 427. Ignited before analysis; includes 0.15 SOo, 0.05 FeS 2 , 0.07 CuO. 
 
 6. Yellow tuff, San Felix, calculated free from H 2 0 and C 0 2 . 
 
 7. Mean of nephelite basanites of San Felix, calculated free from H 2 0 and C 0 2 ; minor constituents 
 neglected. 
 
 If it be assumed that the water and carbon dioxide of the tuff are in large part 
 addition products, and that there has been relatively little loss of the original material, 
 and the analysis is recalculated to ioo per cent on a water-free and carbon-dioxide- 
 free basis, the figures shown in No. 6 of Table II are obtained. Comparison of these 
 with the figures of the two analyses of San Felix nephelite basanite given in Table II 
 
 1 L. V. Pirsson, The microscopical characters of volcanic tuffs—a study for students, Am. Jour. Sci., 
 vol. 40, 1915, pp. 201-208. 
 
San Felix and San Ambrosio 
 
 131 
 
 shows the remarkable correspondence. In the tuff, ferric oxide is higher relatively 
 to ferrous because of oxidation, but the mean of the chief constituents of the two 
 nephelite basanites is remarkably like the recalculated analysis of the tuff, as will be 
 seen on comparing Nos. 6 and 7 of Table IV. 
 
 General Conclusions 
 
 It would appear from the specimens brought back by Willis that the lavas of the 
 San Felix volcano are, so far as known, of only two kinds—a decidedly sodic trachyte 
 and somewhat variable nephelite basanite, which seems to be uniformly highly vitre¬ 
 ous. There is little doubt that the yellow tuff is derived from nephelite basanite 
 magma closely similar to that of the flows. The prominent characteristic of these two 
 types of lava is their high content in alkalies, especially in soda, while high titanium 
 and phosphorus appear to be other constant characters of minor, but still considerable, 
 interest. This conclusion as to the generally highly sodic character of the San Felix 
 lavas is subject to the limitations imposed by the absence of specimens from the lower 
 flows and from various parts of the island. Such basaltic lavas, especially if highly 
 vitreous, may appear megascopically to be very uniform and yet be modally and chemi¬ 
 cally very diverse. It is, therefore, possible that the earlier, lowermost flows are less 
 sodic and more typically basaltic than the upper, which were the ones examined. 
 
 In this predominantly highly sodic character of its lavas San Felix appears to 
 differ widely from other Pacific islands. At Mas-a-fuera, it is true, both soda tra¬ 
 chyte and nephelite basanite, closely like those of San Felix, occur, but these are 
 accompanied by basalt and picrite basalt, whereas at the neighboring Juan Fernandez 
 the lavas appear to be, to judge from Quensel’s descriptions, only olivine basalt, with 
 neither trachyte nor basanite. Trachyte, also highly sodic, occurs at several other 
 Pacific volcanic islands, as do also nephelite basanite and similar rocks high in soda; 
 but at all of them the predominant lavas are more or less normal basalts or andesites; 
 so that the general magmatic character is basaltic—that is to say, sodi-calcic, some¬ 
 what modified by distinctly sodic facies. But this is not the place for a general dis¬ 
 cussion of the Intro-Pacific lavas, and reference may be made to papers by Lacroix, 1 
 Marshall, 2 and Iddings. 3 
 
 One further point may be briefly spoken of. From the field observations made 
 by Willis, especially the inclusion of the trachyte blocks in the yellow tuff and the 
 relations of the tuff and the basanite flows, it would appear that the trachytic lavas at 
 San Felix were earlier, in the sense that lavas of trachyte had been poured out and 
 consolidated before those of basanite, which they must underlie. 
 
 At Mas-a-fuera Quensel noted that the trachyte occupies the higher parts of the 
 island, while the basalt and basanite flows lie below them on the lower parts. He 
 argues from this that “ there had taken place in the volcanic throat a differentiation 
 
 1 Lacroix, Les roches alcalines de Tahiti, Bull. Soc. Geol. France, vol. io, 1910, p. 120. 
 
 2 Marshall, The Geology of Tahiti, Trans. New Zealand Inst., vol. 47, 1915, p. 361. 
 
 3 Iddings, The Petrology of the South Pacific Islands and its Significance, Proc. Nat. Acad. Sci., vol. 2, 
 1916, p. 413. 
 
132 
 
 Earthquake Conditions in Chile 
 
 according to specific gravity.” It is somewhat difficult to follow the reasoning of 
 Quensel, because, if the (supposedly) liquid trachytic magma formed a layer above 
 that of the heavier basaltic magma in the volcanic throat, one might reasonably 
 expect the trachytic flows to have been the first to have been extruded, and so to have 
 formed the lower parts of the volcano, whereas the lower-lying basaltic magmas 
 would have followed these and hence have formed the upper parts of the volcano. 
 Without fairly detailed field observations as to whether the various types of lava 
 issued from lateral vents at different elevations or overflowed the crater edges, it is 
 impossible to discuss such occurrences with intelligence, and in the absence of such 
 observations any generalizations based on such supposed “ sequences ” appear to us 
 to be premature. In any case, the sequence at San Felix appears to be contrary to 
 what Quensel imagines it to have been at Mas-a-fuera. 
 
 It should be said, furthermore, that in these and all such cases we have under 
 our observation only the extreme uppermost tip, an almost infinitesimal part, of a 
 colossal volcano, comparable with the giants of the Andean line, and of which we 
 know, and can know, little or nothing of its lower lavas. It behooves us, therefore, 
 to be cautious in our generalizations, or, still better, to abstain from them until more 
 data are available. 
 
 Basalt of San Ambrosio 
 
 After the preceding pages had been put into type for the article in the Bulletin 
 of the Geologic Society, the specimen of basalt collected by Captain Campbell on San 
 Ambrosio came to hand, and thin-sections and a chemical analysis of it were made. 
 It turned out to be an olivine-free basalt, containing a little orthoclase and nephelite, 
 similar chemically to the specimen of pahoehoe from San Felix, the analysis of which 
 is given in No. i of Table II. 
 
 The rock is very dark gray, almost black, very dense and fine grained, and 
 entirely without vesicles. It is probably from the interior of a thick aa flow. No 
 phenocrysts of any kind are present. Thin-sections show that it is made up largely of 
 a peculiar augite in very small equant anhedra or thin prisms. The color of the augite 
 is somewhat variable, mostly gray with a slightly purplish tone, partly yellowish or 
 light brownish through incipient alteration. Small, thin plates and laths of multiply 
 twinned plagioclase, mostly about Ab2Am to AbiAm, are rather abundant, and there 
 are less well-shaped and generally thicker plates of what appears to be sodic ortho¬ 
 clase; these are mostly untwinned. Small grains of magnetite are present, but are 
 not numerous. No olivine grains are to be seen. There is a small amount of clear 
 colorless basis interstitial in patches; some of this is feebly birefringent and some 
 isotropic. It is probably the nephelite indicated by the norm as present or, in part, 
 glass. The microtexture is typically basaltic, and there is no indication of flow. 
 
 A chemical analysis gave the results shown below. This and the corresponding 
 norm greatly resemble the analysis and norm of the pahoehoe of San Felix, which 
 has been called nephelite basanite because of its content in olivine and the notable 
 
San Felix and San Ambrosio 
 
 133 
 
 amount of nephelite in the norm. Limburgitic basalt would probably be a more 
 appropriate name for this than the one used above. Because of the small amount of 
 nephelite present and the absence of olivine the San Ambrosio lava may best be called 
 tephritic basalt. 
 
 Si 0 2 ., 
 A 1 2 Os 
 F e 2 0 3 
 FeO . 
 MgO 
 CaO . 
 Na 2 0 
 K 2 0 . 
 H 2 0 + 
 
 h 2 o- 
 
 Ti 0 2 . 
 P 2 Os . 
 MnO 
 
 4541 
 
 14-58 
 
 3-22 
 
 874 
 
 4.98 
 9-83 
 3-53 
 2-39 
 0.82 
 0.27 
 5-30 
 1.00 
 n. d. 
 
 Norm 
 
 Orthoclase . 1446 
 
 Albite . 19.39 
 
 Anorthite . 16.96 
 
 Nephelite . 5.40 
 
 Diopside . 20.51 
 
 Olivine . 5.24 
 
 Magnetite . 4.64 
 
 Ilmenite . 10.03 
 
 Apatite . 2.35 
 
 x 00.07 
 
 Tephritic basalt, (III).5"."3.4. San Ambrosio Island, South Pacific. Washington, analyst. 
 
 In the analysis of the San Ambrosio basalt may be noted the rather high alkalies, 
 especially potash, and the high titanium and phosphorus oxides. Both of these last 
 two peculiarities appear to be characteristic of the more fernic lavas (basalt, basanite, 
 etc.) of the Intro-Pacific volcanoes. In the San Ambrosio rock the abundant titan¬ 
 ium is mostly in the augite, as is shown by its peculiar color and the small amount 
 of “ ore.” The resemblance of this analysis to that of the San Felix pahoehoe indi¬ 
 cates the intimate relation of the two volcanic islands. 
 
APPENDIX I 
 
 REPORT ON SEISMOGRAMS OF THE EARTHQUAKE 
 
 OF NOVEMBER 10, 1922 
 
 BY J. B. MACELWANE, S. J., AND PERRY BYERLY 
 
THE EPICENTER OF THE EARTHQUAKE AS DETERMINED BY 
 
 SEISMOGRAPHIC DATA 
 
 It may seem superfluous to discuss the seismographic records of the Chilean 
 earthquake of November io, 1922, in view of the two studies already published by 
 Sieberg and Gutenberg and by the latter alone. 1 However, the authors feel that the 
 more extensive material available to them and their entirely independent analysis 
 of the records and calculation of the epicenter are a sufficient contribution to require 
 publication in this volume if the study of the earthquake is to be complete. 
 
 This instrumental part of the report was undertaken at the request of Professor 
 Willis after he had completed his study of the phenomena in the field but before any 
 of his conclusions were available. Most of the labor of preparing it has devolved upon 
 the junior author. The senior author has been able to do little more than suggest and 
 criticise throughout the progress of the work. 
 
 For the purpose of the location of the epicenter of the earthquake of Novem¬ 
 ber 10, 1922, Professor Bailey Willis has collected from a great number of seis¬ 
 mographic stations throughout the world original seismograms of this earthquake, 
 or copies of them. In addition to these there were available reports from certain 
 other stations. These stations are listed in tables on page 139, and in the last column of 
 each table the nature of the data is given: O representing original seismogram; C, 
 copy; and R, report only. A considerable number of additional records were loaned 
 but these were not suitable for the exact determination of times. 
 
 When the study was first undertaken it was suggested by Professor Willis that, 
 since the field observations pointed to more than one center of violent intensity, the 
 analysis of the seismograms might also point to this same multiplicity of epicenters. 
 Gutenberg 2 has concluded from the study of the records that perhaps three shocks 
 were registered, of which the second originated at a point west of the first. But 
 impulses which arrive after the beginning of the earthquake and which may be due 
 to later shocks at the source are difficult to identify exactly as to time of arrival since 
 they are confused by the motion due to the earlier shock. 
 
 However, the possibility was considered that two shocks from separate foci 
 might have occurred at times so close together that waves from one source would be 
 the first to arrive at stations in one direction while waves from the other source would 
 arrive first at stations in another direction. 
 
 1 A. Sieberg und B. Gutenberg, Das Erdbeben in der chilenischen Provins Atacama am io November 1922, 
 Ver. der Reichsanstalt fur Erdbebenforschung in Jena, Heft 3, 1924; also B. Gutenberg, Bearbeitung der instru- 
 mentellen Aufzeichnungen des Atacamabebens am 10 November, 1922, Nachtrag zu Heft 3. 
 
 2 Gutenberg, loc. cit. 
 
 137 
 
138 
 
 Earthquake Conditions in Chile 
 
 In this study there was a lack of seismograms from stations close to the center 
 of disturbance and the location of the epicenter was thus dependent on observations 
 at distant stations. In such a case, the imperfections of the travel time curves for 
 these distances together with the possibility that at some stations one of the early first 
 preliminary waves of Mohorovicic 1 may have been registered, or perhaps the begin¬ 
 ning of Pn may have failed to register, cause a considerable discrepancy to enter into 
 the computed epicentral distances of the stations. Thus for this earthquake the epi- 
 central distances as computed from the S-P intervals at the various stations fail to 
 reach to a common intersection. The tables given by Gutenburg in Sieberg’s “ Erdbe- 
 benkunde ” were used in the investigation. 
 
 In the first trials an effort was made to reduce these discrepancies by assuming 
 two epicenters, one near Iquique with a time of occurrence of o = 4 — 32 — 42, and 
 the other near Coquimbo and a time of occurrence about 20 seconds earlier. But this 
 did not offer a satisfactory solution. Nor were other efforts to explain discrepancies 
 of computed distances by multiple epicenters successful. 
 
 Finally a group of 26 stations at epicentral distances of less than ioo° were 
 chosen since for such distances our travel time tables are less in error. Where possi¬ 
 ble these stations were selected for the sharpness of the first arrival and the excel¬ 
 lence of the time service, but in certain regions all the stations available were used. 
 
 The times of the arrival of P at these stations were taken and the probability 
 method of Geiger 2 was applied to compute a most probable position of the epicenter. 
 After two adjustments this resulted in placing the epicenter at <po = 29°oo'± 14' 
 Xo = 69°59' ± 19'; and the time of occurrence at to = 411 32m 33s ± 2s U. T. 
 November 11, 1922. 
 
 From the co-ordinates of the various stations and those of the epicenter, the 
 epicentral distance of each station was computed. This distance was then used with 
 Gutenberg’s tables and the expected arrival times of P and S were computed. 
 
 In table 2 are given for the 26 stations used in locating the epicenter the ob¬ 
 served arrival times of P and S together with the differences of the observed and 
 computed values. In table 3 the same data are given for other stations. 
 
 It must be remembered that the epicenter of an earthquake as indicated by the 
 records of seismographs points to the region of the beginning of disturbance and 
 does not at all define the extent of the source. 3 
 
 1 A. Mohorovicic, Rad Jugoslavenske Akadcmije, 1922. 
 
 2 L. Geiger, Herdbestimmung bei Erdbeben aus den Ankunftsseiten, Gottingen, 1910. 
 
 3 H. F. Reid, Starting Points of Earthquake Vibrations, Bull. Seis. Soc. America, vol. 8, pp. 79-82, 1918. 
 
Report on Seismograms 
 
 139 
 
 Arrival Times of P and S 
 
 Station 
 
 A° 
 
 P 
 
 o-c 
 
 s 
 
 O-C 
 
 Data 
 
 Station 
 
 A’ 
 
 P 
 
 1 O-C 
 
 s 
 
 O-C 
 
 Data 
 
 
 
 tn s 
 
 S 
 
 m s 
 
 
 
 
 
 m s 
 
 
 m s 
 
 s 
 
 
 Santiago . 
 
 4-5 
 
 33 35 
 
 — 8 
 
 34 24 
 
 
 0 
 
 Vera Cruz ... 
 
 54-4 
 
 42 02 
 
 — 4 
 
 49 39 
 
 —OI 
 
 R & C 
 
 1 Villa Ortuzar . 
 
 H -3 
 
 35 21 
 
 + 3 
 
 36 36 
 
 + 10 
 
 R 
 
 Tacubaya . 
 
 56.0 
 
 4216 
 
 —03 
 
 49 50? 
 
 —13 
 
 R & C 
 
 I La Paz . 
 
 12.6 
 
 35 40 
 
 + 5 
 
 
 
 R 
 
 Cambridge .... 
 
 71.0 
 
 43 42 
 
 -08 
 
 52 46 
 
 —26 
 
 O 
 
 Rio de Janeiro. 
 
 24.8 
 
 38 00 
 
 — 5 
 
 42 27 
 
 + 4 
 
 O 
 
 foahnnesburg . 
 
 84.0 
 
 45 00 
 
 — 3 ? 
 
 55 33 ? 
 
 — I 
 
 O 
 
 Washington .. 
 
 68.2 
 
 43 33 
 
 + 1 
 
 52 30 
 
 — 4 
 
 C 
 
 Spokane . 
 
 87.7 
 
 44 47 
 
 —37 
 
 55 12 
 
 —6l 
 
 O 
 
 Georgetown ... 
 
 68.2 
 
 43 37 
 
 + 5 
 
 
 
 R 
 
 Coimbra . 
 
 89.7 
 
 45 14 
 
 —21 
 
 56 25 
 
 — 7 
 
 O 
 
 ! St. Louis . 
 
 70.2 
 
 43 45 
 
 + 2 
 
 52 55 
 
 — 3 
 
 O 
 
 Marseilles .... 
 
 99.9 
 
 46 30 
 
 + 3 
 
 57 27 
 
 ?—31 
 
 R & O 
 
 Ithaca . 
 
 7*-7 
 
 43 53 
 
 — 1 
 
 
 
 C 
 
 Oxford . 
 
 100.6 
 
 46 25 
 
 — 6 
 
 
 
 C 
 
 Ann Arbor .... 
 
 72.4 
 
 44 04 
 
 + 8 
 
 5316 
 
 — 8 
 
 O 
 
 West Bromwich 
 
 100.7 
 
 46 23 
 
 -08 
 
 
 
 C 
 
 Chicago . 
 
 72.6 
 
 44 01 
 
 + 3 
 
 53 09 
 
 —19 
 
 C 
 
 Paris . 
 
 IOI.O 
 
 46 34 
 
 +01 
 
 
 
 C 
 
 | Good Hope ... 
 
 73-1 
 
 44 20 
 
 + 19 
 
 53 42 
 
 + 8 
 
 C 
 
 Edinburgh ... 
 
 102.0 
 
 46 33 
 
 —04 
 
 
 
 O 
 
 Northfield .... 
 
 73-2 
 
 44 07 
 
 + 6 
 
 53 31 
 
 — 3 
 
 O 
 
 Uccle . 
 
 103. I 
 
 46 34 
 
 —08 
 
 
 
 C 
 
 Ottawa . 
 
 74-6 
 
 44 11 
 
 + 1 
 
 53 43 
 
 — 8 
 
 C 
 
 Zurich . 
 
 IO3.8 
 
 46 48? 
 
 +03 
 
 
 
 O 
 
 Lick . 
 
 82.1 
 
 44 57 
 
 + 5 
 
 53 03 
 
 - II 
 
 O 
 
 Rocca di Papa. 
 
 IO3.9 
 
 46 45 
 
 —01 
 
 
 
 0 
 
 Berkeley . 
 
 82.8 
 
 44 54 
 
 — 2 
 
 55 21 
 
 0 
 
 O 
 
 Strasbourg .... 
 
 IO3.9 
 
 46 48 
 
 + 02 
 
 
 
 c 
 
 Lisbon . 
 
 88.3 
 
 45 24 
 
 - 4 
 
 56 32 
 
 +13 
 
 O 
 
 OeBilt . 
 
 104.2 
 
 46 41 
 
 -06 
 
 
 
 c 
 
 
 88.7 
 
 45 28 
 
 - 2 
 
 56 36 
 
 + 13 
 
 c 
 
 
 
 46 19 ? 
 
 — 3 ° 
 
 
 . 
 
 0 
 
 Malaga . 
 
 90.0 
 
 45 31 
 
 — 6 
 
 O 
 
 Frankfort . 
 
 IOS.I 
 
 46 49 
 
 —02 
 
 
 
 0 
 
 Victoria . 
 
 90.9 
 
 45 40 
 
 — 2 
 
 56 21? 
 
 —22 
 
 O 
 
 Nordlinger .... 
 
 105-7 
 
 46 S 3 
 
 —02 
 
 
 
 0 
 
 Toledo . 
 
 92.1 
 
 45 49 
 
 0 
 
 56 41 
 
 —13 
 
 C 
 
 Munich . 
 
 106.0 
 
 46 50 
 
 —05 
 
 
 
 0 
 
 
 Q 3.3 
 
 4 s ; 57 
 
 4 - 2 
 
 57 02 
 
 
 O 
 
 
 
 a 6 za.? 
 
 + 20 
 
 
 
 c 
 
 
 04.0 
 
 46 03 
 
 
 57 07 
 
 
 O 
 
 
 108.9 
 
 47 08 
 
 0 
 
 
 
 0 
 
 Cartuja . 
 
 95-5 
 
 45 46 
 
 —20 
 
 
 c 
 
 Batavia . 
 
 144-7 
 
 5210? 
 
 (po—12 
 
 
 
 c 
 
 Tortosa . 
 
 95-5 
 
 45 58 
 
 — 7 
 
 (57 17 ) 
 
 (-3) 
 
 c 
 
 Bombay . 
 
 144.7 
 
 49?47 
 
 — 5 
 
 
 
 0 
 
 Barcelona . 
 
 96.8 
 
 46 09 
 
 — 3 
 
 
 
 c 
 
 Tokyo . 
 
 I 54 -I 
 
 52 33 ? 
 
 (P')—08 
 
 
 
 c 
 
 Honolulu . 
 
 98.6 
 
 46 39 
 
 +18 
 
 57 23 
 
 —24 
 
 c 
 
 Osaka . 
 
 157-7 
 
 52 52 
 
 (P 04 
 
 
 
 R & C 
 
 Balboa . 
 
 39-1 
 
 40 27 
 
 +11 
 
 
 
 0 
 
 Manila . 
 
 162.4 
 
 52 49 
 
 (PO— 4 
 
 
 
 C 
 
 Vieques . 
 
 47-4 
 
 41 02? 
 
 —16 
 
 
 
 c 
 
 Hong Kong ... 
 
 172.3 
 
 52 50 
 
 (PO —7 
 
 
 
 c 
 
APPENDIX II 
 
 DISTRIBUTION OF INTENSITIES 
 
 By DR. LUIS SIERRA VERA 
 
Note. Dr. Luis Sierra of Copiapo, a devoted student inspired 
 by Comte Montessus de Ballore, undertook the labor of analyzing 
 the responses to the questionnaires, which were sent out to secure 
 information regarding the personal experiences and observations 
 of the inhabitants in the shaken region. The three hundred answers 
 have been summarized in an earlier part of this volume (pages 42 
 to 45), but no attempt was there made to evaluate the intensities at 
 different points. To this task Dr. Sierra brought special experience 
 and knowledge of his countrymen. His digest of the data and his 
 estimates of intensity, expressed in terms of the Rossi-Forel scale, 
 are given in the following tables. The localities are arranged in 
 order of latitudes, from north to south. B. W. 
 
 142 
 
Distribution of Intensities 
 
 Distribution of Intensities 
 
 143 
 
 d 
 
 u 
 
 25 
 
 to 
 
 <u 
 
 73 
 
 43 
 
 to 
 
 3 
 
 <L> . 
 
 <U V 
 U V 
 
 bo v« 
 u to 
 •O v 
 73 
 
 rG 
 
 %•& 
 > bo 
 c/)W 
 
 1> . 
 
 <D D 
 
 h, <d 
 bO p 
 (U bfl 
 73 <D 
 
 o ±; jd o 
 
 Q g^P 
 5.9 
 
 C/3 W 
 
 bo 
 
 <d 
 
 72 
 
 SP 
 
 > 
 
 c/3 
 
 o 
 
 p 
 
 ° o 
 
 pp 
 
 o 
 
 p 
 
 bo 
 
 D 
 
 73 
 
 43 
 
 bO 
 
 3 
 
 o 
 
 p 
 
 bo 
 
 43 
 
 bo 
 
 3 
 
 <u 
 
 u 
 
 P 
 
 bfl 
 
 O 
 
 P 
 
 bo o 
 G +* cii' CJ 
 ^ o CTJp 
 
 £ 
 
 f 
 
 bO 
 
 CO 
 
 4*5 
 
 O 
 
 rt 
 
 G 
 
 rt 
 
 > 
 
 tM 
 
 0 d 
 
 G 
 
 43 
 
 M 
 
 73 
 
 G 
 
 Vp O 
 
 c 
 
 ? 
 
 rt 
 
 r 5 
 
 bfl 
 
 42 C 
 .tJ O 
 
 6*^ 
 
 43 ^ 
 
 •p cj 
 
 0 
 
 • M C# 
 
 •43 0 
 
 B 
 
 rt 
 
 72 
 
 O 
 
 0 
 
 
 * 
 
 • £ 
 
 73 
 
 tM 
 
 CO 
 
 72 72 
 §» 
 
 •a h 
 
 l § 
 
 ■d " 
 
 § « 
 
 O to 
 
 Wood 
 
 zinc 
 
 42 
 
 0. 
 
 72 
 
 < 
 
 43 43 
 G bO 
 0*42 
 £c/3 
 
 >, *}.ajd 
 »~3 C bO bO 
 G O ; -1 • 
 
 Q£ C/3 C/3 
 
 43 43 
 G G 
 O O 
 
 43 
 
 G 
 
 o 
 
 £ 
 
 0) 43 
 G G 
 o o 
 
 <D 
 
 G 
 
 o 
 
 £ 
 
 V 
 
 
 0 
 
 
 jj 
 
 2 
 
 rt 
 
 
 42 
 
 rt 
 
 
 42 
 
 rt 
 
 8 
 
 
 « a 
 v 
 
 6 
 
 D 
 
 73 
 
 P 
 
 43 
 
 p 
 
 n 
 
 
 a, 
 
 to 
 
 a 
 
 
 
 0, 
 
 
 CL 
 
 • 
 
 0 
 
 < 
 
 if) 
 
 < 
 
 
 0 
 
 G 
 
 o 
 
 K 
 
 u O 
 
 P O 
 O ^ 
 
 o 
 
 G 
 
 43 O 
 
 M P 
 
 V 
 
 73 
 
 g rt 
 ° bo 
 £ 
 
 • 73 
 
 I G 
 
 72 
 
 G 
 
 •73 
 
 : c 
 
 . rt 
 
 • 43.G . 
 
 I G N *2 o 
 
 Cj C 
 
 : S 1 *-* i-p 
 
 O ^ EM 
 
 73 rr'n <»72 
 O 4_» o G G 
 0 *h ^ h rt 
 
 *- G 
 1 rt ^ 
 
 CJ 
 
 <u 
 
 G 
 
 CO 
 
 u 
 
 , 0 *rp'73 
 
 p^ 3 
 
 • o G 
 
 £ 
 
 o 
 
 o 
 
 \-i 
 
 73 
 
 G 
 
 Cj 
 
 72 
 
 G 
 
 C3 
 
 d 
 
 G 
 
 rt 
 
 u 
 
 > CO to 
 
 * .2_g «73 
 
 •a S.2o^ g 
 
 g.G p.72 o g 
 
 k? N cj Gt 2 £ 
 
 £ H < 
 
 73 . 
 O • 
 O • 
 
 OJ CJ 
 
 a^a 
 
 2 S 5 
 
 
 73 
 
 O 
 
 O 
 
 £ 
 
 73 
 
 G 
 
 rt 
 
 42 
 
 o 
 
 72 
 
 < 
 
 72 
 
 G 
 
 G 
 
 O 
 
 p 
 
 o 
 
 72 
 
 v 
 
 42 
 
 O 
 
 CO 
 
 73 
 
 G 
 
 G 
 
 O 
 
 C/3 
 
 P 
 
 “1 
 
 G g 
 
 * g G 
 
 St: 
 
 p <D 
 
 > 
 
 S 
 
 .5 
 
 ’> 
 
 G 
 
 a 
 
 d 
 
 4> 
 
 43 
 
 bo 
 
 jq 
 
 c /5 
 
 o 
 
 C/3 
 
 *72 
 
 : g 
 
 . rt 
 
 rt 
 
 <D 
 
 W 
 
 73 
 
 G 
 
 3 
 
 in 
 
 o 
 
 in 
 
 72 
 
 <D 
 
 42 
 
 <D n3 
 
 1=3 
 
 G 
 G 
 
 gIE w.T. 
 
 — 72 <3 T2 
 
 Pc/) < c/3S>c/3 
 
 o 
 73 P 
 
 O • 
 If) • 
 
 j* 
 
 a -m 
 0.73 
 Wc/3 
 
 o 
 
 C/) 
 
 >» 
 
 <u 
 
 >> 
 
 cj 
 
 0 
 
 o 
 
 a 
 
 G 
 
 • H 
 
 > 
 
 G 
 
 o 
 
 p 
 
 o 
 
 p 
 
 rt> 
 +-» 
 o o 
 
 ^ B 
 
 P 
 
 id 
 
 o 
 
 <L> 
 
 4*5 
 
 42 
 
 G 
 
 O 
 
 o 
 
 4*5 
 
 cc) 
 
 >» 
 
 > 
 
 1) 
 
 44 
 
 O 
 
 P 
 
 bfl 
 
 G 
 
 ’u 
 
 a 
 
 o 
 
 o 
 
 44 
 
 >» 
 
 > 
 
 C3 
 
 <L> 
 
 43 
 
 .72 
 • G 
 G 
 o 
 
 72 
 G 
 G 
 
 Vh Ui L 
 CM bo 4J bfl <y 
 
 O Vh 73 Ih rr~i 
 
 (DJ3 ^ c 
 U 'S 5? G 
 *5 -g ^ ^ G M 
 
 V P h « b U 
 
 gd gris 
 
 P C^Pq^P 
 
 G 
 
 o 
 
 G, 
 
 V 
 
 44 
 
 rj 
 
 <D 
 
 U 
 
 U 
 
 * v 
 
 * ID g 
 P’S ^ 
 w c 
 
 ■oE" 
 
 G 
 
 2«^ 
 
 -5a 
 
 cd 
 
 V V u 
 
 XrX'Z. 
 
 PP 
 
 b 
 
 72 
 
 G 
 
 G 
 
 43 
 
 a* 
 
 p 
 
 t: 
 
 o 
 
 a 
 
 o 
 
 G 
 
 <D 
 
 44 
 
 <D 
 
 72 
 
 G 
 
 £% 
 
 *-i m 
 
 <D 
 
 43 <D 
 
 p 
 
 CS 
 
 o 
 
 D 
 
 44 
 
 73 
 
 i 
 
 O 
 
 H 
 
 o 
 
 G 
 
 73 
 
 u 
 
 d 
 
 £ 
 
 o 
 
 H 
 
 o 
 
 P 
 
 G 
 
 
 
 
 
 * 
 
 
 
 
 
 
 
 
 
 I CO of 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 : ^ j; 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 0 
 
 
 
 
 
 q 
 
 
 
 
 
 
 
 
 
 • p 
 
 _ 72 *9 
 
 
 *D 
 
 
 
 *CJ 
 
 <D 
 
 2 : 
 
 
 2 
 
 
 2 
 
 vp 
 
 
 
 •3 d <-> 
 
 72 6 
 
 »M 
 
 
 Vp 
 
 <-M 
 
 
 <4-* 
 
 
 «+4 
 
 
 
 
 
 
 ^ & 
 
 53 tJ 
 
 bfl 
 
 
 bo 
 
 bO 
 
 ?! MMM . 
 
 bfl 
 
 
 bfl 
 
 bO 
 
 bo 
 
 Q 
 
 G 
 
 
 G 
 
 G C 
 
 P C 
 
 SCO 
 
 3 C 
 
 
 G 
 
 G C 
 
 O 
 
 .5 <n ?! 
 
 <0 w 
 
 3 4J 
 
 <L 
 
 2 
 
 2 P 2 222P 
 
 5° i 
 
 43 43 2 P 
 
 p 
 
 43 2 d ^ d 
 
 •a u 
 
 0 0 
 
 
 0 
 
 0 
 
 « c 
 
 0 0 
 
 
 0 . c 
 
 0 c 
 
 O 
 
 0 4) rt (U 
 
 CO 
 
 z fe: 
 
 'z 
 
 
 Iz 
 
 p : 
 
 £ 
 
 
 z:z ^ : : 
 
 Z H H 
 
 
 M 
 
 
 
 
 
 
 
 
 
 
 
 
 
 6 
 
 to 
 
 D 43 
 c. bo 
 
 £ 
 
 0 
 
 • M 
 
 2 « 
 
 G S 
 
 0 v~> 
 
 
 £ 
 
 0 
 
 to 
 
 O 
 
 O to 
 
 CO 
 
 CO 
 
 to 
 
 to 
 
 
 to 
 
 
 
 to to 
 
 to to to to 
 
 to 
 
 7" 
 
 
 
 7- 
 
 to 
 
 7- 
 
 
 w B 
 
 A 
 
 p 
 
 42 M 
 
 : < 
 
 
 *H M 
 
 *-« *H *-H t-t 
 
 J= 
 
 M 
 
 H 
 
 M M 
 
 l-H 
 
 M 
 
 p 
 
 M 
 
 
 t-l *H 
 
 M M »H H« 
 
 M 
 
 
 
 l-« M 
 
 M 
 
 b-t 
 
 p 
 
 G 
 
 O 
 
 a 
 
 o 
 
 B 
 
 rt 
 
 G 
 
 cr 
 
 c4 
 
 CJ 
 
 u 
 
 G 
 
 ctJ 
 
 to 
 
 CJ 
 
 m 
 
 cd 
 
 c3 
 
 73 
 
 N 
 
 o 
 
 S 
 
 G 
 
 o 
 
 •2 
 
 PN 
 
 U <D 
 
 G^ 
 bo o 
 
 G o 
 
 QJ C_j 
 
 a .S 
 
 <D W. 
 to rt 
 
 <D 
 
 P 
 
 2 
 
 *rt 
 
 I 
 
 o 
 
 o 
 
 « 
 
 (A 
 
 .2 C 
 
 3 
 P 
 
 2§ 
 
 d 
 
 .a C 
 
 pLi 3 
 
 CO 
 
 G 
 
 «4T 
 
 O G 
 
 B.2* 
 
 p p 
 <D C 
 
 ffiw 
 
 »o ^ I cd 
 2 £m° 
 
 gas i 
 
 iC'-'O-l <D 
 
 Oh w s 
 
 c 
 
 S H 3 J. 
 rt m-^'p 
 
 
 rt 
 
 ? l - 
 £ 
 
 d _o 
 ^G O 
 *7 O 
 
 O 1 ^ 
 O 1> 
 .2 G 
 o o* 
 
 S’C 
 2 c 
 p p 
 
 m 
 
 o 
 
 73 
 
 CJ 
 
 p 
 
 *G cJ 
 
 .Sp 
 
 G 
 
 s* 
 
 I B 
 
 cj a> 
 G 43 
 fe*G 
 
 WO 
 
 d 
 
 m 
 
 73 
 
 in 
 
 d 
 
 G 
 
 < 
 
 .2 
 
 *G 
 
 « 
 
 G 
 
 cJ 
 
 P 
 
 w 
 
 a 
 
 .2 
 
 *+3» 
 
 G 
 
 rt 
 
 C/3 
 
 42 
 
 < s 
 
 2 K 
 
 <4 a 
 
 G 
 
 t: 
 
 c 
 
 o 
 
 4> 
 
 G 
 
 4: 
 
 rt 
 
 cj 
 
 s 
 
 ip?. Js 
 
 N . 8^3^ 
 
 ^ vo' *o 2 ^ 2 
 
 O n 5 . 
 •gS'S'S 0 fe 
 
 0 g .t: cj vo ^ > 
 
 •S.G t*o>^<D-r 
 ^ 13 g,2 .ts 
 
 ^22 4> w 
 03 w 
 
 bfl 
 
 ^ CO 
 (N 7- . 
 
 c* rt 
 o a> 
 
 M (/) 
 
 > ^ 
 
 1 4 ; c -r - 
 2^r rt’w 
 
 2-B.2 ^|aa 
 
 'S-S^^s-S 
 
 O' 
 
 
 o 
 
 rt 
 
 a> 
 
 42 
 
 G to 
 
 ^ o 
 
 8 
 
 » 7- 
 
 ,^S 
 
 v'® V a 
 O CJ 72 O 
 W 72 G 
 
 •7 M 
 
 bfl 
 
 .s 
 
 .-*bo 
 
 G 
 
 co’p 
 
 C»M ^ 
 
 C C 
 
 8^ 
 
 ^ CO 
 CO tO . 
 
 o rt 
 o c; 
 to 
 
 m <D 
 to t2 
 rt 
 c 
 u 
 
 G 
 
 rt 
 
 QJ 
 
 
 to 
 
 Gh 72 G § 'o > 
 ^ C.G rt ►- rt 
 
 S.tJ 
 
 Pm C ^ -p ^0 
 
 1> C 
 
 u’S.o 
 
 rt"S S ti <u 
 
 p 3-3 ra > 
 u ^ rr 
 
 
 w — o 
 
 s-r^ f 
 
 rti3^ 4) 
 
 tX) > C J43 o 
 C Ur-• M *•“* ^ 
 
 M tO ... ~ 
 
 . °o>'8 O | a 
 
 r\v5 rt- co^ ,r - 
 
 04 l> c S'rtJS 
 D 73 0^43 o 
 
 g,-H 
 
 3^3 oU 'w 
 
 14 
 
Distribution of Intensities— Continued 
 
 144 
 
 Earthquake Conditions in Chile 
 
Distribution of Intensities— Continued 
 
 Distribution of Intensities 
 
 145 
 
 be 
 
 <v 
 
 G 
 
 33 
 
 to 
 
 W 
 
 o o 
 
 QQ 
 
 4> 
 
 4> 
 
 I* 
 
 <u 
 
 G 
 
 bfl 
 
 33 
 
 to 
 
 O 
 
 P 
 
 bo 
 
 4> 
 
 .g 
 
 o 
 
 P£ 
 
 c 
 
 33 
 
 bfl 
 
 55 W 
 
 £ w 
 
 bo 
 
 4 ; 
 
 G 
 
 bo 
 
 4) 
 
 G 
 
 33 
 
 bo 
 
 o o o o 
 
 QQ PP 
 
 £S 
 
 bfl 
 
 4> 
 
 G 
 
 33 
 
 4-* 
 
 # g 
 
 s 
 
 •d 
 
 bo 
 
 W 
 
 c 
 
 <u 
 
 > 
 
 4> 
 
 C/2 
 
 bfl 
 
 41 
 
 G 
 
 t: o o 
 
 £qq 
 
 > 
 
 4> 
 
 <n 
 
 to bfl 
 
 33 
 
 4-» 
 
 G 
 
 G 
 
 V 
 
 P 
 
 bo 
 
 33 
 
 bfl 
 
 W 
 
 <1 
 
 <u . 
 
 V- <U 
 be 4> 
 
 <u i - 
 73 bo 
 
 4> 
 
 45*0 
 
 Cj3 
 
 <U -H* 
 
 > G 
 C/3« 
 
 £ <y 
 fc. « 
 
 bfl i_ 
 
 bo 
 G OJ 
 
 •s’? 
 
 bo G 
 
 •-« 4) 
 
 PP 
 
 33 O 
 
 2^ 
 
 bo 
 
 w 
 
 bfl 
 
 4> 
 
 'a 
 
 33 
 
 bo 
 
 £ W 
 
 4> 
 
 be 
 
 G 
 
 i 
 
 G 
 
 p 
 
 -Q 
 
 cO 
 
 -O 
 
 G 
 
 8 «. 
 
 2 M 
 
 ex 
 
 ex 
 
 < 
 
 . 8 
 •G U 
 bfl CX 
 
 :g ex 
 C/)< 
 
 *3 
 
 ex 
 
 ex 
 
 < 
 
 
 • 0 
 
 
 4) 
 
 
 
 
 
 
 ' 32 
 
 
 32 
 
 
 
 * .2 
 
 
 
 4) J? 
 
 V 
 
 G 
 
 U 
 
 32 
 
 G 
 
 i) • 
 
 .32 
 
 G 
 
 G 
 
 u. 
 
 c 
 
 G 4) 
 
 u G 
 
 G 
 
 u 
 
 4) 
 
 G 
 
 
 2d 
 
 dg 
 
 4> 
 
 G 
 
 c 
 
 ■SI 
 
 O 
 
 G 
 
 "cO 
 
 Ih 
 
 a 
 
 
 P E 
 
 . ex 
 
 *co 
 
 
 2o 
 
 2 
 
 O 
 
 CJ 
 
 ex 
 
 < 
 
 1 : 
 
 • ex 
 :< 
 
 O 
 
 U 
 
 33 
 
 bfl 
 
 v 
 
 G 
 
 O 
 
 £ 
 
 • bfl 
 
 :.S 
 
 •2 
 
 •’3 
 
 : 32 
 
 a; a; a; 
 G G G 
 o o o 
 £££ 
 
 32 
 
 G 
 
 C 
 
 4> 
 
 g 
 
 *5> 
 
 G 
 
 c3 
 
 32 
 
 G 
 
 +j 
 
 2 
 
 G 
 
 33 
 
 .5 
 
 *G 
 
 & 
 
 33 
 
 bfl 
 
 CO 
 
 2 
 
 G 
 
 t4 
 4> 
 G 
 
 G G 
 
 o § 
 
 fcCJ 
 
 32 
 
 * G 
 
 4J E 
 
 •a G 
 
 .sra 
 
 c?)D 
 
 G 
 
 G 
 
 o 4> 
 
 sts 
 
 c h 
 DO *i 
 — G 
 co o 
 
 .52 
 
 •O 
 
 G 
 
 u 
 
 <u 
 
 g 
 
 *53 
 
 G 
 
 o 
 
 U 
 
 4> 
 
 G 
 
 «-t 
 
 <u 
 
 G 
 
 O 
 
 2 
 
 G 
 
 g g 
 g.2 
 g 
 
 ■8 
 co -ti 
 a; G 
 32 bo 
 o 3 
 
 73 u 
 
 * G 
 
 ! o 
 d S 
 c £ 
 
 rt 
 
 °-d 
 
 *5 5 
 
 X* 
 
 G 
 
 G 
 
 o 
 
 G 
 
 G 
 
 G 
 
 G ^ . 
 Gjg | 03 
 
 q O Vh*Q, 
 
 >< H 
 
 o 
 
 £ 
 
 G 
 
 G 
 
 rt 
 
 co 
 
 <u 
 
 32 
 
 O 
 
 G 
 
 • 4) 
 
 : c 
 
 •§ s 
 
 2g 
 
 G 
 
 G G 
 G 
 
 8 
 
 s-§ 
 
 rt-a 
 
 U<3 
 
 •G 
 
 O 
 
 I 
 
 V 
 
 -Q 
 
 O 
 
 T3 
 
 •d . 
 c G 
 
 G o 
 
 'G'G 
 3 a> 
 
 6 G 
 I bfl 
 
 r V, t ^ 
 2 o 2 
 ►S So 
 
 i ^ ^ 
 
 3 
 
 G 
 
 •G O 
 
 c.t: 
 
 G 
 
 T3 
 
 *t3 ii'G 'G’G 
 
 S G O O O 
 
 0.000 
 
 o 
 
 o 
 
 -G 
 
 | .*§ 
 |o rt 
 
 *G o 
 G U 01 
 
 "G 
 
 ’ G 
 G 
 
 i.§-§! 
 
 mNrt N 
 
 o G a 
 •G Gr3 
 < (-> 
 
 •o H'O'O 
 o n o o 
 
 cQ 
 
 i|-§ 
 : ? 6 
 
 • 0*73 
 
 • S C 
 
 • G G 
 X 
 
 *+-» CO 
 <D 
 
 g-S 
 
 *G 
 
 c G 
 G § 
 
 G 4> *G 
 C GGJ 3 
 
 G§ 
 
 c £ J? 
 
 O G 
 
 *G 
 
 G 
 
 G 
 
 T3 
 
 O 
 
 o 
 
 . £ 
 
 -G 73 
 cq g 
 
 ? o 
 
 bo co to „ 
 
 3 «u cj to 
 
 l_, * »G H r\ 
 
 O cx^ 0.3 
 
 U oj G 73 N 
 
 H < 
 
 •G 
 
 G 
 
 3 
 
 O 
 
 - 
 
 o 
 
 G3 
 
 > 
 
 rG 
 
 O 
 
 CO 
 
 G3 
 
 G 
 
 3 
 
 o 
 
 3 
 
 
 
 3 
 
 
 •;g 
 
 3 
 
 2 0 
 
 * 3 
 
 * 3 
 
 ^3 
 
 < 
 
 Q 
 
 Wash 
 
 > 
 
 ^3 
 
 < 
 
 Q 
 
 CO 
 
 G 
 
 O 
 
 *> 
 
 ^3 
 
 < 
 
 £ p 
 
 3 . 
 
 35 • 
 
 < : 
 
 Firm 
 
 Alluvi 
 
 Firm 
 
 Alluvi 
 
 > 
 
 3 
 
 •G 
 
 G 
 
 G 
 
 ^ G 
 o G 
 O g 
 
 05 
 
 o 
 
 o 
 
 a 
 
 w* 
 
 E 
 
 s 
 
 E. 
 
 E 
 
 ^4 
 
 o 
 
 O 
 
 o 
 
 CO 
 
 o 
 u 
 
 ^'G’G 
 o V3 
 O o O 
 ps5 co co 
 
 G 
 
 .2 
 
 *> 
 
 3 
 
 o 
 
 CO 
 
 GG 
 
 o o 
 
 coco 
 
 si 
 
 co< 
 
 73 > 
 
 ;g g 
 o ^ 
 coO 
 
 o 
 
 P 
 
 o 
 
 in 
 
 >> 
 
 > 
 
 G 
 
 u 
 
 o 
 
 j-. 
 
 ex 
 
 isS 
 
 “ o 
 
 JZ 
 
 ^ Co 
 
 S «"S 
 
 rt . O s 
 
 TJ'S 3 
 
 t3 O 
 
 o bo 
 
 ® § £ £ 
 
 O 
 
 P 
 
 u 
 
 V 
 
 'G 
 
 G 
 
 3 
 
 ■*-* 
 
 <U 
 
 ri4 
 
 >» 
 
 > 
 
 G 
 
 : >> 
 
 o 
 
 p 
 
 o o 
 
 PP 
 
 *G G • 
 
 O tl 
 
 *ns g 
 
 G3 O 
 
 r> j 
 
 u 
 
 V 
 
 •G 
 
 G 
 
 3 
 
 rG 
 
 <U 
 
 34 
 
 >» 
 
 G 
 
 <D 
 
 34 
 
 •G 
 
 G 
 
 3 
 
 rG 
 
 4-* 
 
 (D 
 
 34 
 
 «u 
 
 34 
 
 P P 
 
 P P 
 
 U 
 
 QJ 
 
 GJ 
 
 G 
 
 >» 
 > 
 G 
 0 J 
 
 33 
 
 <L> 
 
 > 
 
 ^ tJ 
 r3 o 
 P 
 
 > 
 
 G 
 
 U 
 
 <V 
 
 •G 
 
 G 
 
 G 4-* 
 
 <U 
 
 34 
 
 O 
 
 34 
 
 P P 
 
 • bo 
 
 co.S 
 
 §§ 
 
 G 
 
 o ™ 
 
 'OJ J 
 
 G 
 
 .2 
 
 G 
 
 G 
 
 O 
 
 tj 
 
 <u 
 
 •G 
 
 G 
 
 3 
 
 <U 4) G D 
 34 34 £34 
 
 PP P P 
 
 34 
 
 G 
 
 O 
 
 P 
 
 'S 
 
 co 10 
 G G 
 V <U 
 
 V « 
 
 G-S 
 
 O O 
 
 HH 
 
 o 
 
 P 
 
 3 
 
 O 
 
 G 
 
 O 
 
 H 
 
 «L> 
 
 s 
 
 O 
 
 ■P g 
 4> S 
 
 fcx Hfe 
 
 33 
 
 o 
 
 G 
 
 O 
 
 H 
 
 G 
 
 £ 
 
 o 
 
 H 
 
 3 
 
 O 
 
 CO 
 
 G 
 
 4) 
 
 *G 
 
 h 
 
 G 
 
 £ 
 
 O 
 
 H 
 
 3 
 o 
 co 
 
 s-s 
 
 o rt 
 
 s ^ 
 
 G o 
 
 >H 
 
 CO 
 
 3 
 
 .2 
 
 *n 
 
 G 
 
 > 
 
 33 
 
 4-> 
 
 3 
 
 8 
 
 G 
 
 £ 
 
 O 
 
 H 
 
 3 
 
 o 
 
 CO 
 
 •G 
 
 u 
 
 G 
 
 o 
 
 H 
 
 CO ^ 
 G ^ 
 <u ^ 
 
 G GJ 
 u Cl 
 G G 
 £ £ 
 0.0 
 HH 
 
 CO 
 
 u 
 
 : 1-5« 
 
 :t°Z 
 
 : o r 
 
 |S^ 
 
 _ 
 
 • <u 
 : ^ 
 
 *G 
 
 u< 
 
 G 
 
 £ 
 
 O 
 
 H 
 
 oj G 
 u v 
 
 •3 3 
 
 3 O 
 rT > 
 
 ^ o 
 
 3 
 
 o 
 
 w 
 
 rt -A 
 
 Us 
 
 ►j -jrr to 
 ^ 41 
 
 G 
 
 G 
 
 G 
 
 co 
 
 .P 
 
 S| g 
 
 G 
 G 
 G 
 . co 
 
 CO 4) 
 
 si 
 
 i? 
 
 G 
 
 G 
 . G 
 co G 
 
 JS CO 
 
 3 ^ be 
 G O 
 
 «; 0 
 
 ■ 
 
 O o 
 
 'C.H .;T3 o 
 h i y B h 
 rt u J. Kja 
 
 ^5p“ 
 
 v to . 
 
 .ss 8 >.33 
 
 32 oj 32 ►> C“ ^ -*-> 
 
 g w o J S 3 o*r 
 
 O 3 u 8 GVM C ^ 
 
 pa ffiS C 
 
 G 
 
 G 
 
 G 
 
 o 
 
 « 
 
 co 
 4) 
 
 228 
 "2 5 ”3 
 
 ^ O 
 > tn 
 
 V 
 35 
 OG 
 i O 
 G Mh 
 h 
 
 G a) 
 
 ^ E 
 
 3.S 
 
 0 x 1 
 
 . G 
 CO O 
 4) 
 
 i2 v 
 
 o 
 
 ■*-> 
 
 <u 
 
 CO 
 
 *G 
 
 •33 
 
 o 
 
 ~ o 4J . 
 i2 ^ CO 
 t>G • 4> 
 
 3^ w G 
 CQ> H 
 
 <L» 
 
 30 
 
 O 
 
 u 
 
 G 
 
 - 
 
 G 
 
 £ 
 
 10 
 
 rt 2 
 
 bfl 
 
 .5 
 
 4 ; 
 
 4J 
 
 33 
 
 bfl 
 
 .2 
 
 to 
 
 .5 
 
 OAS 0 
 
 E 
 
 -+-* 
 
 2 
 
 2 
 
 « O-S 
 
 ■*-» 
 
 0 
 
 G 
 
 O 
 
 55 
 
 0 
 
 0 
 
 CQ 
 
 
 
 < 
 
 
 
 4) 
 
 Ih 
 
 3 
 
 G 
 
 u 
 
 3 
 
 .33 o 
 
 • G V, 
 
 • o O 
 
 co ^ co 
 O to O 
 X 4>G 
 
 ^•§2 
 
 u +* 
 4)G» 
 
 gS| 
 
 Ok 
 
 <L» (0 
 73 ^ 
 *5532 
 G 
 
 . co 
 . <u 
 
 : *o^ 
 
 G S * 
 
 Is! 
 
 O 
 
 *cj a; 
 
 be; 
 G c 
 
 4-> O 
 
 o-S 
 
 zu 
 
 bo 
 
 G 
 
 30 
 
 G 
 
 u 
 
 e 
 
 O IO 
 
 PO 
 
 
 
 4-> 
 
 O 
 
 s 
 
 to 
 
 T- 
 
 to to 
 
 to to 
 
 to 
 
 6 
 
 0 
 
 
 VO 
 
 vo 
 
 
 to 
 
 s 
 
 to 
 
 O 
 
 to 
 
 O to 
 
 to 0 
 
 • • E 
 
 • • 00 
 
 ■7 
 
 
 to ^ 
 
 to 
 
 
 
 to O 
 
 to 
 
 to 
 
 to 
 
 to -7 
 
 ■7 to 
 
 
 to 
 
 
 to 
 
 to 
 
 
 to 
 
 to 
 
 to 
 
 
 to to 
 
 
 
 
 A 
 
 M bh 
 
 
 
 
 11 
 
 Ab 
 
 12 
 
 HI 
 
 A 
 
 _ 
 
 HI HI 
 
 W HI 
 
 
 - £1 
 
 HI 
 
 
 M 
 
 HI 
 
 
 _ 
 
 •c 
 
 HI 
 
 _ 
 
 HI 
 
 HI HI 
 
 HI HI 
 
 1 1 ■‘j. 
 
 M 
 
 M 
 
 HH ►H 
 
 
 M 
 
 HI 
 
 HI 
 
 HI 
 
 HI 
 
 HI HI 
 
 HI HI 
 
 HI 
 
 HI 
 
 
 
 HI 
 
 
 IH 
 
 HI 
 
 
 HI 
 
 HI HI 
 
 HI HI 
 
 
 
 l 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 G 
 
 
 . . 
 
 I * • 
 
 
 u 
 
 6 
 
 G 
 
 G 
 
 G 
 
 bfl 
 
 G 
 
 G 
 
 V 
 
 P 
 
 23 
 
 15 .S 
 
 5^ 
 
 t—) o 
 
 3 a 
 
 E 3 
 
 rtu 
 
 cofa 
 
 3 
 
 a 
 
 w 
 
 o 
 
 G 
 
 pa 
 
 o 
 
 S 
 
 * G 
 G G 
 G p. 
 
 
 4> 
 
 G 
 
 < 
 
 3 
 
 o 
 
 G 
 
 > 
 
 O 
 
 G 
 
 u 
 
 G 
 
 O 
 
 2 
 
 <D O 
 
 WG 
 
 . 2 ^ 
 
 G 
 
 eS 
 
 < G 
 
 4) 
 
 G 
 
 4) 
 
 2 
 
 ° 3 
 
 B a 
 
 E< « 
 i-;c 2 
 
 OJ 
 
 o 
 
 N 
 
 G 
 
 4) 
 
 U 
 
 O 
 
 P 
 
 o 
 
 G 
 
 G 
 
 O 
 
 s 
 
 G 
 
 N 
 
 1 -, 
 
 <u 
 > 
 o 
 
 32 G 
 cj G 
 X W V 
 
 - . o 
 
 o 
 G_h 
 
 4> 
 
 Ph 
 
 o 
 
 CO 
 
 o 
 
 G 
 
 G G 
 
 »+-i <D 
 
 "G 
 co G 
 
 OJ 32 
 
 CH 
 
 ^-§ 
 
 E « 
 
 E 3 
 
 dT3 
 
 3 u ra-a 
 -,Ph UbJ 
 
 rt 
 
 K 
 
 V** 
 
 .s 
 
 u 
 
 G 
 
 2 
 
 O 
 
 G 
 
 G 
 
 O 
 
 G 
 
 4> 
 
 & 
 
 G 
 
 G 
 
 N 
 
 OJ 
 
 3 
 
 O 
 
 o 
 
 u 
 
 G 
 
 <u 
 
 P 4 
 
 o 
 
 G 
 
 G 
 
 G 
 
 G 
 
 . G 
 32 Xh 
 0 4) 
 
 w^S 
 
 Jh 
 
 < -u 
 
 in ’ in 
 
 G 
 
 1 
 
 > t, Uh^.H 
 
 it rt 
 G p 
 
 G 
 
 ► 
 
 4) 
 
 3 
 
 G 
 
 G 
 
 O 
 
 G 
 
 G 
 
 > 2 
 
 a S 
 
 VH 
 
 .S3 ^ 
 
 3 
 
 P P* 
 
 G 
 O 
 
 N G 
 
 3f< 
 
 3 U O 
 
 s 
 
 O 
 
 G 
 
 O 
 
 D 
 
 o c 
 
 u. o 
 
 ^ G 
 4> « 
 
 G 
 
 O 
 
 .2 N 
 3‘p 
 
 O 0 
 
 o o 
 G ^ 
 
 gg 
 
 W. o 
 
 PP 
 
 • u 
 
 • o 
 
 :h 
 
 <j § 
 
 S?.2 
 
 23 
 
 G 
 
 . u. 
 
 PPQ 
 
 G 
 
 3 
 
 bfl 
 
 G 
 
 4) 
 
 s 
 
 < 
 
 4) 
 
 P 
 
 G 
 
 rt 
 
 £ 
 
 o 
 
 p 
 
 3 
 
 P 
 
 P 
 
 ^J2 
 
 ••* rH d» 
 
 .v *"N 
 
 ^ o 
 
 C. O N^&C “ 
 o kN •-•O R rt > 
 V 4) c c W H 
 
 41G o « ^ S bfl 
 '<2 ^ H *^J O w O 
 P.O.'S cj n 3 ^ 
 
 .2-2 c « ”2 E 5 
 
 &js|-a -a 
 
 1 
 
 G 
 
 T* 
 
 2 sr* SM 
 
 g « c S ,23 
 
 J3 u'g o o C3 
 
 , "SsS o o > 
 
 - 3.t! c« o; a 
 2.tJ 60> 4 -w, 
 u *. C " bo 
 iu 1 ? ov -a 
 
 C'2 
 
 M I 
 
 O G 
 
 o ® V 
 
 .®o ^ CO 
 
 G^ ^ 
 
 W 
 
 4) 
 
 CO 
 
 G 
 
 O 
 
 o 
 
 >> 
 
 34 
 
 o 
 
 O 
 
 G 
 
 l> G O • - 
 
 ■g’SI’-s^ 
 
 •c-- «« 
 
 b ti c O'- 1 A. 
 
 -a 
 
 u w 
 
 ts, *h I 
 <S G 
 o oj 
 
 SoS.". 
 
 v G 
 
 ojG o 
 
 ^5*- 
 
 G 
 
 O 
 
 o 
 
 >> 
 
 34 
 
 v o'8 
 
 8 s.|'p S 
 
 CO ^ 
 
 O O 
 
 4> 
 
 CO Nil 
 ^ V a 
 
 CS^ 
 
 o'R o • 
 
 :c- 
 
 C M * U G 
 
 .S 7*C*. <® co . 2 
 
 bo > f oT ^ 
 
 .2 T! 2T £ E « G 
 
 •5*3 G C 
 JJ G o 
 
 P°^ 
 
 V 
 
Distribution of Intensities— Continued 
 
 146 
 
 Earthquake Conditions in Chile 
 
 qj 
 
 qj 
 
 u 
 
 to 
 
 QJ 
 
 G 
 
 G 
 
 QJ 
 
 H 
 
 QJ 
 
 o 
 
 u 
 
 to 
 
 •G 
 
 to 
 
 bfl 
 
 QJ 
 
 G 
 
 O 
 
 Q 
 
 P £ 
 
 o 
 
 qj 
 
 H 
 
 be 
 
 QJ 
 
 G 
 
 P 5 
 
 G 
 
 H 
 
 o 
 
 Q 
 
 o 
 
 P 
 
 <L 
 
 QJ 
 
 l. 
 
 bo 
 
 QJ 
 
 G 
 
 -G 
 
 bo 
 
 w 
 
 o 
 
 Q 
 
 o 
 
 Q 
 
 bfl 
 
 QJ to 
 -rt a; 
 
 G 
 
 -G 
 
 •m -G 
 -G 
 bO 
 
 S 55 
 
 o 
 
 Q 
 
 to 
 
 qj 
 
 G 
 
 G 
 
 QJ 
 
 H 
 
 o 
 
 Q 
 
 o 
 
 P 
 
 o 
 
 p 
 
 c7 bo 
 
 ■o ■§ 
 
 2 -a 
 
 J3 
 to 
 
 W 
 
 G 
 
 P 
 
 qj <u 
 <JJ qj 
 u U 
 
 to to 
 <v <v 
 GG . 
 
 S-Sp 
 
 o 
 
 p 
 
 o 
 
 p 
 
 o 
 
 p 
 
 o 
 
 p 
 
 QJ 
 
 to 
 
 g 
 
 £ 
 
 g 
 
 P 
 
 . 
 
 
 
 
 
 I 
 
 
 
 
 
 
 
 
 QJ 
 
 -C 
 
 
 
 
 
 QJ 
 
 
 QJ 
 
 bfl 
 
 
 
 aj 
 
 
 QJ 
 
 
 
 QJ 
 
 bfl 
 
 
 
 -d 
 
 # G 
 
 CJ 
 
 G . ‘ 
 
 G O QJ 
 
 
 
 
 CO 
 
 3 
 
 
 E 
 
 
 V 
 
 P 
 
 
 1q 
 
 
 QJ 
 
 G 
 
 i 
 
 G 
 
 JJ 
 
 
 QJ 
 
 c 3 
 
 
 
 
 3 
 
 G 
 
 M 
 
 
 G 
 
 G 
 
 rt 
 
 QJ 
 
 -Q 
 
 G 
 
 G 
 
 -*-* 
 
 
 G 
 
 M 
 
 QJ 
 
 -Q 
 
 G 
 
 -Q 
 
 2 
 
 QJ 
 
 
 (X 
 
 ex 
 
 o . cd 
 
 O G m 
 
 
 
 
 
 -Q 
 
 
 
 Li 
 
 QJ 
 
 
 
 
 M 
 
 rt 
 
 QJ 
 
 
 
 G 
 
 •s^-g 
 
 
 
 G 
 
 -G 
 
 .5 
 
 ’£ 
 
 Li 
 
 V 
 
 G 
 
 O 
 
 > 
 
 G 
 
 QJ 
 
 >» 
 
 Li 
 
 <U 
 
 G 
 
 "co 
 
 G 
 
 -G 
 
 .£ 
 
 *G 
 
 C 
 
 P 
 
 -G 
 
 .5 
 
 *G 
 
 u 
 
 QJ 
 
 G 
 
 O 
 
 G 
 
 "co 
 
 G 
 
 >> 
 
 > 
 
 G 
 
 QJ 
 
 G 
 
 "co 
 
 G 
 
 rt 
 
 p 
 
 »-* 
 
 QJ 
 
 « Sc 
 
 C 
 
 P 
 
 C 
 
 P 
 
 o 
 
 p 
 
 3 
 
 D 
 
 g 
 
 
 > 
 
 CJ 
 
 D 
 
 
 D 
 
 g 
 
 o 
 
 W 
 
 CJ 
 
 c/5 > 
 
 ^ D 
 
 • 
 
 
 o 
 
 •Q 
 
 rt 
 
 rt 
 
 -C 
 
 .5 
 
 3 
 
 D 
 
 £ . 
 -G 
 
 co 
 
 JG 3 
 
 -§i 
 
 ? .« 
 to g 
 
 E OJ3 
 
 G G ±i 
 
 £ a > 
 
 _.-a <U 
 ^ ™J 2 Tj 
 
 8 So a 
 
 £ w-a cj 
 
 > <3 
 
 v •« 
 ■§ .§ 
 ^ o . 
 
 rt e-g 
 
 o g 
 S'n „ 
 
 2 Cl G o 
 cd G-rd 
 
 h c 
 
 g 
 
 o 
 
 o 
 
 £ 
 
 G 
 
 G 
 
 G 
 
 g3 
 
 qj ~ 
 
 4-» rt 
 
 ft 
 
 bo co 
 rt QJ QJ 
 
 E .2 o,a 
 o oG o 
 CJ cd GG 
 
 H <3 
 
 ■ 2 - 2 . 2 -a.S 
 
 a 2 n o. G o 
 br cd rt-a 
 
 ' H <3 
 
 / O) N " « pui M W « 
 O tfl ^ tj ri « « « ^ V 
 
 o qj g v E E_,j2 
 
 g-q P,5^o 
 
 .-oFoinOScdcj ci.rG n 13 
 
 bo-*-* S+>►? 03 
 < < > H > 
 
 G 
 
 G 
 
 9 
 
 o 
 
 Li 
 
 a 
 
 6 
 
 2 
 
 ’> 
 
 3 
 
 6 
 
 g 
 
 O ^ 
 
 
 
 QJ 
 
 Li 
 
 
 
 
 
 0 2 
 u 3 
 
 
 G 
 
 
 
 
 
 
 to G 
 
 
 
 s 
 
 
 to £ 
 
 . bfl 
 CJ-G 
 
 s 
 
 O 
 
 E : 
 
 E 
 
 : E 
 
 o 
 
 o 
 
 u3-H 
 
 C 
 
 
 
 o 
 
 
 cm 
 
 P 
 
 J3 
 
 • ^ 
 
 Q 
 
 Q 
 
 to co > 
 
 S3 S2 
 
 o 1 
 
 c 
 
 s 
 
 Li 
 
 > 
 
 o 
 
 h rt-a 
 
 a ^ rt 
 
 > 
 
 G 
 
 QJ 
 
 > 
 
 ^2 
 
 > 
 
 ^2 
 
 > 
 
 ^2 
 
 * 
 
 • 
 
 U <3 
 
 
 P 
 
 < 
 
 
 CJ g 
 
 <3 
 
 m 
 
 < 
 
 <3 
 
 <3 
 
 -Q 
 
 O 
 
 CO 
 
 G 
 
 G 
 
 3 
 
 O 
 
 C/3 
 
 QJ 
 
 rX 
 
 a 
 
 u 
 
 G 
 
 G 
 
 O 
 
 Li 
 
 bfl 
 
 Li 
 
 QJ 
 
 .G | 
 
 c G QJ 
 G 0 p 
 
 *m £ 
 
 i) o 0 ) 5 
 
 S^-S 
 
 P P 
 
 L. 
 
 <U 
 
 nG 
 
 G 
 
 G 
 
 *G 
 
 <L) 
 
 O 
 
 P 
 
 
 •Q £ 
 G 
 
 2 >> 
 g u > 
 u G ?? 
 O TG 
 CM C’ 
 
 <D^ V 
 
 p p 
 
 
 >» 
 
 > 
 
 •G 
 
 <L> 
 
 *G 
 
 <D 
 
 : 
 
 "•S 3 
 
 •a ° 
 
 G g Li 
 
 S © « 
 
 4J 2 ^ 
 rt G 3 
 
 5 
 
 riS g r^J 
 P P 
 
 *G 
 
 G 
 
 G 
 
 •G 
 
 0 ) 
 
 . 4> 
 
 . co 
 
 I o vi 
 o 
 
 v 5 
 
 ^ t 
 
 G 
 
 rt 
 
 jn c; 
 co^G 
 
 m-3 
 
 V g 
 J 2 
 
 nG 
 
 Li 
 
 G 
 
 £ 
 
 O 
 
 h 
 
 G 
 
 O 
 
 H 
 
 G 
 
 o 
 
 'O 
 
 P 
 
 G 
 
 CJ 
 
 G 
 
 O 
 
 H 
 
 o 
 
 c ^3 
 
 B* 
 
 O O 
 L, W 
 
 P 
 
 G 
 
 # o 
 
 "l 
 
 G 
 
 > 
 
 G 
 
 .2 
 
 *u 
 
 G 
 
 > 
 
 G Li 
 
 5 O 
 P G 
 
 * 
 
 
 
 
 
 -a 
 
 
 
 
 
 -M 
 
 
 
 
 ■M 
 
 P 
 
 
 G 
 
 
 CO 
 
 o 
 
 • 
 
 
 
 G 
 
 CO 
 
 • 
 
 Li 
 
 
 QJ 
 
 G 
 
 * 
 
 CM * 
 
 • *5 G 
 
 
 
 QJ 
 
 
 Li 
 
 G 
 
 
 -G 
 
 C 
 
 G 
 
 fs 
 
 
 ■M 
 
 L. ^ 
 
 O 
 
 
 O 
 
 rt 
 
 O 
 
 H 
 
 
 H 
 
 > 
 
 H 
 
 QJ "G 
 
 L V 
 
 P > 
 ^ o 
 
 G 
 
 o 
 
 w 
 
 CO 
 
 <L> 
 
 Li 
 
 «« 3 
 ° .2 
 “> to m p> 
 U -M <U 
 
 > c > >> 
 u 313£ 
 — CJ3 S3 
 to o to o 
 
 U § 
 
 OJ 
 
 o. 
 
 2 2 
 
 o c+-« 
 
 o a; Li cj bfl 
 -Q » G G 
 
 •"£ %-~ ’5 
 Sege^ 
 
 G*rt i3 ^ 
 •*-* L G CJ 
 c/i G '-m > 
 
 > w 
 
 •G 
 
 G 
 
 G 
 
 CO , 
 <D W 
 L« ^ 
 
 •“t - , 
 
 2 
 
 G 
 
 a) 
 
 -Q 
 
 o 
 
 -o 
 
 G 
 
 H 
 
 g 22 
 .2 2 -^ 
 p 
 
 fl) cy 
 
 C. ■*£ 
 
 
 bO 
 
 G . 
 
 +3 <D 
 
 L J3 
 <D g 
 
 w 
 
 ■g-f 
 
 G C 
 
 <L> Z G = 
 
 bfl 
 
 .s 
 
 IB 
 
 % 
 
 QJ 
 
 G 
 
 g <D 
 H 
 
 • to 
 3G <d 
 
 rt ^ 
 cm O 
 
 ■£2 O O 
 
 O Li 33 c 
 G G <d£ 
 
 ^ < 
 
 G . 
 ^2 
 
 G 
 
 J?G 
 g <D -G 
 co 
 
 .t: co mP 
 
 p P’S O 
 
 = -l E 
 
 L g 
 
 
 I CJ* 
 
 
 O 
 
 
 
 • QJ 
 
 : > 
 
 * QJ 
 
 
 G 
 
 • 
 
 
 
 3 CO 
 
 
 G 
 
 3 
 
 
 
 cm L. 
 bc’rt 
 
 
 G 
 
 cm 
 
 bfl 
 
 
 -M ^ 
 
 G 
 
 C -G 
 o 
 
 aj3d 
 
 QJ 
 
 G 
 
 
 o 
 
 p 
 
 < 
 
 G 
 
 O 
 
 •a 
 
 
 bO 
 
 G 
 
 O 
 
 .-G ^ 
 
 or « 
 P CJ2 
 
 • QJ-Q 
 
 • > G 
 
 :wh 
 
 ■ES 
 
 rt 5 
 
 *G «—« 
 
 G •—^ Li 
 Li G l> 
 
 G **■* > 
 
 P w 
 
 O O 
 
 P P 
 
 < S 
 
 c; -G 
 
 *- bo 
 
 «0 o • — 
 
 10 2 G 
 
 M ^G 
 
 “ n E 
 
 (D 
 
 S 
 
 G 
 
 £ 
 
 . 
 
 
 
 
 
 
 
 
 
 .2 
 
 
 
 gn 
 
 
 
 CO 
 
 QJ 
 
 d 
 
 
 0. 
 
 Q 
 
 o 
 
 u 
 
 *C 
 
 2 
 
 
 rt 
 
 o 
 
 CO 
 
 rt 
 
 cm 
 
 .2 
 
 Li 
 
 O 
 
 co 
 
 G 
 
 CJ 
 
 Q 
 
 N 
 
 .2 
 
 -2 
 
 QJ 
 
 G 
 
 G 
 
 
 N 
 
 G 
 
 bfl 
 
 u 
 
 3 
 
 3 
 
 P 
 
 3 
 
 Li 
 
 *5. 
 
 3 
 
 Li 
 
 Li 
 
 O 
 
 G 
 
 u 
 
 o 
 
 Li 
 
 QJ 
 
 *G 
 
 G 
 
 > 
 
 
 G 
 
 G 
 
 o 
 
 « 
 
 U 
 
 G 
 
 H 
 
 G 
 
 > 
 
 H 
 
 3 
 c n 
 
 G 
 
 < 
 
 O 
 
 G 
 
 o 
 
 G 
 
 Li 
 
 Li 
 
 P 
 
 G 
 
 G 
 
 CO 
 
 .2 
 
 o 
 
 G 
 
 .2 
 
 3 
 
 o 
 
 .£ 
 
 CJ 
 
 CO 
 
 3 
 
 O 
 
 G 
 
 G 
 
 > 
 
 c7) 
 
 G 
 
 3 
 
 G 
 
 P 
 
 Ivan 
 
 G 
 
 Q? 
 
 < 
 
 Li 
 
 G 
 
 CJ 
 
 rt 
 
 N 
 
 O 
 
 -M 
 
 CO 
 
 3 
 
 o 
 
 G 
 
 QJ 
 
 co 
 
 Li 
 
 c 
 
 3 
 
 G 
 
 G 
 
 LH 
 
 *n 
 
 QJ 
 
 CM 
 
 QJ 
 
 U 
 
 CJ 
 
 G 
 
 G 
 
 Li 
 
 P 
 
 3 
 
 CJ 
 
 co 
 
 G 
 
 P 
 
 L 
 
 G 
 
 CJ 
 
 P 
 
 G 
 
 o 
 
 G 
 
 G 
 
 G 
 
 ert 
 
 G 
 
 -id 2 
 
 O O o 
 
 o 
 
 G 
 
 G 
 
 G 
 
 G 
 
 ^g t: ^ 
 -C c M u 
 
 ^ s a-P 
 
 G 
 
 o 
 
 « 
 
 1 > 
 
 G 
 
 G 
 
 P 
 
 G 
 
 « 
 
 «L> 
 
 £ 
 
 CJ 
 
 p 
 
 V 
 
 G 
 
 P 
 rt • 
 
 G w 
 qc rt 
 
 2 G 
 
 Q 
 
 rt 
 
 s 
 
 U 
 
 .2 
 
 •s 
 
 6 
 
 u 
 
 w 
 
 "O 
 
 Ah 
 
 rt 
 
 E 
 
 rt to 
 
 m 3 
 
 c C 
 •2 L 
 
 n 
 
 bo 
 
 3 
 
 < 
 
 w 
 
 N 
 rt 
 
 t N m 
 u 
 
 P?P V 
 
 Cog 
 o o 
 
 u 
 
 GOO 
 
 §e| 
 
 PP P 
 
 G 
 
 -Q 
 
 G 
 
 u 
 
 rt 
 
 <u 
 
 3 
 
 O 
 
 P 
 
 QJ 
 
 G 
 
 QJ 
 
 G 
 
 <u 
 
 G 
 
 a 
 
 rt 
 
 .£ 
 
 *G 
 
 G 
 
 O 
 
 s 
 
 <3 
 
 G 
 
 O 
 
 P 
 
 d 
 
 G 
 
 -G 
 
 rt 
 
 L 
 
 -G 
 
 < 
 
 V 
 
 a 
 
 rt 
 
 P 
 
 G 
 
 G 
 
 £, 
 
 ^G c £ 
 . <L)G o r 
 
 cl 
 
 2,2 QJ 
 
 QJ 
 
 > 
 
 . 08 ^, 
 
 G 
 
 ^ rt M > U 
 
 P -C ^ 
 
 jSS 2 
 bo>^fl5 
 
 ^3 1) s - / _*L G 
 
 H* o’ 
 
 >' 
 
 o o 
 
 -g rt |± 3 >« 
 
 QJ g 2 
 
 ■“«« rt^ 
 
 1 ) > 
 
 ■2.2 e 5 
 
 C P O O G 
 
Distribution of Intensities— Continued 
 
 Distribution of Intensities 
 
 147 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
APPENDIX III 
 
 GEOLOGY OF ATACAMA 
 
 OUTLINE OF THE ESSENTIAL FACTS OF THE GEOLOGIC PLAN AND 
 
 STRUCTURE OF THE PROVINCE 
 
 By JOHANNES FELSCH 
 
 GEOLOGIST, BUREAU OF MINES AND GEOLOGY, CHILE 
 
 (Translation) 
 
GEOLOGY OF ATACAMA 
 
 The disastrous earthquake of November io, 1922, by which the cities of Copiapo, 
 Vallenar, and Chanaral were partially destroyed, and in consequence of which the 
 entire population of the province of Atacama has suffered greatly, has led to a study 
 of the geologic causes of the severe and frequent shocks experienced in that region. 
 
 The earthquake of November 10 caused a great movement of the sea all along 
 the coast from latitude 31 0 south to latitude 21 0 . This great disturbance of the sea, 
 extending more than a thousand kilometers from north to south, in itself proves that 
 the vibrations of the earth’s crust were very strong in the sea-bottom as well as on 
 the land. The town of San Antonio, situated in the valley of the Copiapo River, at a 
 distance of a hundred kilometers from the coast, was almost completely destroyed. 
 It thus appears that the earthquake was of great extent from east to west as well as 
 from north to south, and it is obvious that the shock was caused by tectonic move¬ 
 ments that affected the western coast of the continent. 
 
 A fault of important magnitude had been observed at a point 2 km. west of 
 Vallenar and another at a distance of 9 km. east of Copiapo, in the course of a geo¬ 
 logic reconnaissance executed by the author for the purpose of finding water-supply 
 for the railroad. These faults have a course of N. 15 0 E. Nearly all the faults 
 encountered in the course of this reconnaissance in the western slope of the Cordil¬ 
 lera in the province of Atacama have a similar direction. Furthermore, the greater 
 part of the numerous metalliferous veins in the province have a similar strike and 
 the fractures in which the vein-matter was deposited were originally caused by tec¬ 
 tonic pressure. 
 
 The first visit (after the earthquake) to the cities of Vallenar and Copiapo in 
 January, 1923, showed plainly that the houses facing on north-south streets had suf¬ 
 fered much more than those on east-west streets. 
 
 An incident that occurred in the house of Don Felipe Matta in Copiapo during 
 the earthquake clearly demonstrated that the shocks of the earthquake were oriented 
 in a direction perpendicular to the above-mentioned points, that is to say, that the 
 shocks had a causal relation to the faults. At the time of the earthquake there stood 
 in the house of Senor Matta a sideboard with a polished top. It was placed against a 
 wall which ran N. 30° E., and on it was a heavy bronze fruit-dish standing on three 
 feet. In consequence of the shocks the fruit-dish danced from southeast to northwest 
 and fell from the western edge of the sideboard to the ground, after having recorded 
 its march across the varnished top quite clearly by the scratches made by its feet. 
 The scratches show that the fruit dish moved from S. 66° E. to N. 66° W., that is to 
 say, perpendicular with reference to a line running N. 24 0 E. 
 
 With these facts in mind, I began my study of the region between Caldera and 
 Copiapo. 
 
 151 
 
152 
 
 Earthquake Conditions in Chile 
 
 In the coast, about 25 km. southwest of Caldera, opposite a large island, I encoun¬ 
 tered a reverse fault which is readily visible and has a course of N. 35 0 E. It was 
 traced throughout a length of 40 km. The block to the west of the fault is overthrust 
 about 18 meters upon the block to the east. Both masses are covered with sandstone, 
 probably of Pliocene age, and the displacement of this stratum facilitates the recog¬ 
 nition of the uplift on the fault. The fault being so young, it is well marked in the 
 morphology of the surface. The Morro of Copiapo which bounds the plain of the 
 Quaternary terrace between Monte Amargo and Caldera on the west, owes its exis¬ 
 tence chiefly to this fault. 
 
 The fault may also be observed where it is indicated by disturbances of the 
 Pliocene beds in the southern part of the Bahia Inglesa, 15 km. southeast of Caldera. 
 Small springs occur along the line of the fault in Chorrillo, opposite the large island, 
 in the southern border of the Bahia Inglesa and in the Aguada de Leon, 15 km. 
 northeast of Caldera. The Aguada de Leon gives off a little hydrogen sulphide. 
 
 Fifteen kilometers west of Monte Amargo, the valley of the Copiapo is nar¬ 
 rowed by an outcrop of gneiss that projects above the Quaternary terrace. The alti¬ 
 tude of the latter at this point is 108 meters. Between the narrows of Monte Amargo 
 the floor of the valley is formed by beds of shells and sands of Pliocene age partly 
 covered by Quaternary deposits. In the narrows the bottom of the valley has an 
 altitude of 65 meters. The Pliocene with Ostrea maxima occurs at an altitude of 
 108 meters, on top of the gneiss, and the same Pliocene stratum occurs at a level of 
 80 meters only 120 meters east of the narrows. Thus it is evident that the narrow 
 has resulted from the elevation of the gneiss, as is proved by the position of the 
 stratum with Ostrea maxima on the east of the fault and on the west of it. 
 
 To the north and to the south of Monte Amargo the marine shell beds of Plio¬ 
 cene age constitute terraces that have an altitude of 240 meters; 5 km. west of Monte 
 Amargo the Pliocene terraces terminate along a line that has a general north-south 
 course. The calcareous beds are almost horizontal. I11 the narrows, which are men¬ 
 tioned in the preceding paragraph, the Pliocene beds dip gently toward the east in 
 such a manner that they disappear under the Quaternary deposits that constitute the 
 banks of the river to within 5 km. of Monte Amargo. It thus appears that the Plio¬ 
 cene terraces to the north and south of Monte Amargo are cut off along their western 
 edge by a fault which has a throw of 103 meters. 
 
 Thus it is demonstrated that the coastal zone between Caldera and Monte 
 Amargo is traversed by three faults which run approximately parallel with a N. 35 0 
 E. course. The first of these faults extends from the Chorrillo through the Bahia 
 Inglesa and Caldera to the Aguada de Leon and occasions an elevation of the western 
 block by 18 meters over the eastern block. The second fault occurs at the narrows 
 and has raised the western block about 28 meters above the eastern. The third fault 
 has caused the western block to drop 103 meters below the eastern. 
 
 These modern faults have, in fact, a course that is perpendicular to that indi¬ 
 cated by the fruit-dish in the house of Senor Felipe Matta in Copiapo in consequence 
 of the movements in the shock of November 10, 1922. 
 
Geology of Atacama 
 
 153 
 
 My preliminary studies had already led me to this conclusion toward the middle 
 of March 1923, when there came to Copiapo Professor Bailey Willis, of Stanford 
 University, in California. He was charged with the duty of making a study of the 
 earthquake of November 10, 1922, and the undersigned received instructions from 
 the Director of Mines and Geology to assist Professor Willis in that investigation. 
 During the months of May and June we conducted a reconnaissance of the Rio 
 Copiapo from Monte Amargo to the head of the Rio Manfias, of the Quebrada de 
 Paipote as far as its head in the western slope of the Cordillera, and also in the valley 
 of the Rio Huasco from its head in Laguna Grande to its outlet to the sea (also the 
 valley of the Elqui from Rivadavia to La Serena). 
 
 In the course of these excursions the undersigned directed his observations 
 especially to the identification of the stratigraphic horizons of this part of Atacama. 
 Professor Willis took special note of the structural geology. The accompanying map 
 presents the results of our reconnaissance. 
 
 Inasmuch as the undersigned has more specially studied the stratigraphy, the 
 following report is devoted particularly to a description of the rock formations that 
 make up the geologic column of the province. 
 
 The province of Atacama may be divided into three zones, which are distin¬ 
 guished by their morphology as well as by the strata of which they are composed: 
 
 (1) The coastal zone constitutes a belt along the coast, having in the latitude 
 of the valley of Copiapo a width of 54 km. It narrows little by little toward the north, 
 but widens toward the south. It consists geologically of metamorphic rocks of Paleo¬ 
 zoic age, upon which rest unconformably sediments of the upper Tertiary, which are 
 found, however, only in a few places. This coastal zone is a mountain range which 
 parallels the coast and reaches altitudes of 800 meters. 
 
 (2) As a second zone, we may designate the western slopes of the Cordillera 
 Real as far west as the eastern border of the coastal zone. It is composed in large part 
 of marine sediments of Mesozoic age, which are frequently intruded by basic igneous 
 rocks and tuffs of similar composition. Furthermore, at the close of the Mesozoic 
 and the beginning of the Tertiary there were intrusions and extrusions of the acid 
 igneous rocks of the Andes in the foothills of the Cordillera. 
 
 (3) The third zone lies in the summit plateaus of the Cordillera Real and is 
 made up of lavas and tuffs, the products of modern volcanic eruptions. 
 
 The metamorphic rocks of Paleozoic age that constitute the mass of the coastal 
 zone also constitute the basement rocks beneath the Mesozoic sediments in the foot¬ 
 hills of the Cordillera. This Paleozoic basement may be found here and there in the 
 slopes of the Cordillera Real at the bottom of deeply eroded valleys. Outcrops of the 
 Paleozoic basement are especially common along the tectonic fault-lines. 
 
 The basement rocks of Paleozoic age comprise the following: (1) Gneiss. (2) 
 Mica schists, slates, and quartzites. (3) Granites and plagioclase granites, that often 
 form large massive intrusions in the metamorphic schists. Thus, 2 km. south of the 
 port of Chanaral there is an extensive outcrop of an intrusion with a cover of black 
 slates. Apophyses of the granite penetrate the slates. (4) Intrusions of black diabase 
 
154 
 
 Earthquake Conditions in Chile 
 
 that are highly metamorphosed, and which occur in the Paleozoic basement, probably 
 also belong to the Paleozoic. On the other hand, the obscure dikes of porphyry that 
 frequently cut the masses of gneiss and Paleozoic granite represent plutonic rocks of 
 Mesozoic age. They are especially frequent in the Paleozoic granite that is exposed 
 in the Quebrada of the Rio Salado between Chanaral and Carmen. 
 
 MESOZOIC HORIZONS 
 
 The Mesozoic strata lie unconformably upon the basement rocks of the Paleo¬ 
 zoic. Forty-three kilometers east of Pueblo Hundido in the Quebrada del Rio Salado 
 the Paleozoic gneisses are overlain by the gray limestones of Neocomian age. 
 Generally, however, there is a layer of basal conglomerate or of conglomeratic sand¬ 
 stone between the limestones and the Paleozoic gneiss. These basal conglomerates 
 testify to the activity of the waves of the Neocomian sea before the limestones were 
 deposited. Three kilometers east of Paipote in the valley of Copiapo the gneisses and 
 mica schists are covered by beds of labradorite porphyry, and these in turn are over- 
 lain by the limestones of the Neocomian. At the point known as Las Juntas, which 
 is at the confluence of the Rio Jorquera and the Rio Manfias, the Paleozoic gneisses 
 are covered by a quartz porphyry over which extend conglomeratic sandstones with 
 chunks of petrified trees and frequent plant remains. The latter indicate that the 
 conglomerates belong to the Rhetic. The thickness of the continental sediments is 
 60 meters more or less. Upon these in turn lie calcareous sandstones followed by 
 gray limestones with many fossils. Vola alata (Bush) is especially common. The 
 fossils demonstrate the lower Jurassic or Liassic age of the calcareous sandstones 
 and gray limestones. In the Quebrada de Iglesia, on the eastern bank of the Rio 
 Manfias, the Liassic strata are overlain by red sandy limestones that are of middle 
 Jurassic or Dogger age, according to the brachiopods and corals which they contain. 
 
 These reddish gray limestones carrying the same Middle Jurassic fossils are 
 succeeded in the Quebrada de Paipote by reddish marls. Six kilometers upstream 
 from the Hacienda la Puerta, in the Quebrada de Paipote, the grayish red limestones 
 of the Middle Jurassic form an anticline that rises in the floor of the Quebrada. On 
 both limbs these limestones of the Dogger are overlaid by bedded lavas of labra¬ 
 dorite porphyry having a thickness of 70 to 100 meters and over the porphyry there 
 come reddish gray marls. In the Quebrada de Jorquera also there are eruptions of 
 labradorite porphyry overlying the Dogger. In general, eruptions of labradorite 
 porphyry accompany the sediments of the Middle Jurassic. 
 
 Pyroxene porphyries and breccias are found 1,200 meters downstream from 
 the Hacienda la Puerta, in the Quebrada de Paipote, overlying the red marls. 
 Furthermore, at Chimbero, 20 km. north of the Quebrada de Paipote, there occur 
 eruptions of pyroxene porphyry melaphyre in association with black limestones and 
 black calcareous slates, which, according to the fossils that they contain, belong to 
 the horizon of the Tithon of the upper Jurassic. It may be said that eruptions of 
 melaphyre are almost always associated with the sediments of the upper Jurassic. 
 
Geology of Atacama 
 
 155 
 
 To the Neocomian we may assign the eruptives and dikes of diabase that occur 
 in association with greenish gray and reddish sandstones. The latter are overlaid 
 by gray limestones with fossils characteristic of the Neocomian. 
 
 Fossiliferous sediments of later age than the Neocomian limestones have not 
 been found by me in the Cordillera of the province of Atacama. 
 
 POST-NEOCOMIAN INTRUSIONS 
 
 Intrusions of quartz diorite, of diorite without quartz, and flows and dikes of 
 amphibolite andesite and pyroxene andesite have, without doubt, occurred subse¬ 
 quent to the deposition of the Neocomian limestones. In Chimbero, ioo km. north 
 of Copiapo and in the Chanarcillo, 60 km. south of Copiapo, the Neocomian lime¬ 
 stones in contact with intrusions of diorite are metamorphosed into aphanitic marbles 
 with garnets. In other places, as, for example, in the valley of the Rio Huasco between 
 Toro and Caracol, the intrusions of diorite have produced contact metamorphism 
 with Jurassic horizons. 
 
 The eruptions of andesite are in general more recent than the intrusions of 
 diorite. One frequently encounters dikes of andesite that cross the mass of diorite. 
 The acid eruptions of trachyte and liparite are the most recent in the region of the 
 foothills of the Cordillera Real. In the upper stretches of the Quebrada de Paipote, 
 at the place called El Obispo, there occurs an eruption of trachytic breccia immedi¬ 
 ately above an overthrust fault by which the red marls of the Middle Jurassic are 
 thrust over a large flow of amphibolite andesite. 
 
 It thus appears that at this point the eruptions of trachyte are more modern 
 than the andesite. The outflows of liparite and trachyte are especially closely con¬ 
 nected with the tectonic lines in the western slope of the Cordillera. In the upper part 
 of the western slope of the Cordillera the eruptions of liparite constitute large lava- 
 flows which are frequently accompanied by white masses of liparite tuff. The liparite 
 flows in this region cover the deposits of gravel that fill the Tertiary valleys. Lavas 
 or tuffs of more recent age than the liparite flows do not occur in the western slope 
 of the Cordillera in the province of Atacama. 
 
 The high Cordillera was not visited by me during this trip. It is probable that 
 the terraces in the vicinity of Monte Amargo, that contain beds of limestones with 
 lamellibranchs which were described in the introduction to this report, are but little 
 younger than the eruptions of liparite. 
 
 It is appropriate to state that the excursions were made very rapidly and that it 
 was not possible to take sufficient time to ascertain by looking for fossils the age of 
 all of the horizons seen. Especially in the valley of the Rio Huasco it is possible that 
 there may be mistakes in the distribution or age of the formations shown in the 
 geologic map. Nevertheless, the general geologic character of the more important 
 tectonic lines was definitely ascertained. Thus, for instance, in the case of the over¬ 
 thrust which occurs 9 km. east of Copiapo, the Paleozoic gneisses are found to rest 
 upon Neocomian limestones. The overthrusts in the Quebrada de Paipote were recog¬ 
 nized upon evidence of equally satisfactory character. 
 
156 
 
 Earthquake Conditions in Chile 
 
 Thus, as a result of these reconnaissance studies, it is recognized for the first 
 time that the province of Atacama is characterized by a geological structure consist¬ 
 ing of overthrust sheets between which the faults strike N. 25 0 to 35 0 E. There is 
 much to be done to complete these studies in the future, and there will then be oppor¬ 
 tunity to correct such mistakes as may have resulted from the reconnaissance nature 
 of the work which is the basis of this report. 
 
APPENDIX IV 
 
 GEOLOGIC NOTES 
 
 BY BAILEY WILLIS 
 

 
 
COPIAPO VALLEY BELOW COPIAPO 
 
 Place —Monte Amargo and vicinity, a railway station in the valley of the Copiapo 
 River. 
 
 Position —Longitude 70 3 41' to 4 J°, latitude 27° 21' to 22° S. 
 
 Observations —At a point 4 km. east of Monte Amargo a tributary of the 
 Copiapo has cut a channel about 10 meters deep in beds of sand, peat and diatoma- 
 ceous earth. The strata are intimately and irregularly interstratified. The peat is a 
 sponge of loose roots with some carbonized layers. It is very light and not compacted. 
 The bed rock is not exposed. 
 
 Monte Amargo station, elevation 137 meters above sea; a well sunk for water 
 encountered peat. The nearby banks of the river show peat under 10 meters of sand. 
 (See Plate L.) 
 
 The hill called Monte Amargo is on the northern side of the valley and consists 
 of granite with diabase intrusions (spec.). The following observations were made 
 on the joints in the diabase: Strike N. 42 E. magn.; dip 55 SE.; strike N. 67 W., dip 
 80 S.; strike N. 18 E., dip 48 W. 
 
 At a point about 5 km. west of Monte Amargo the heights of the river terraces 
 on the north bank were measured with hand level. Taking the flood plain as datum 
 they were: Lower terrace 8 meters, capped with calcareous tufa or caliche; upper 
 terrace 70 meters. Gypsum is quarried from the lower terrace between this point and 
 Monte Amargo. 
 
 The course of the Rio Copiapo to and beyond Monte Amargo to the sea is 
 straight west. It flows through a canyon (angostura), however, in the outer Coast 
 Range. Thus the character of the valley, which is recently filled at Monte Amargo 
 and is incised below that point indicates recent uplift. 
 
 Place —Toledo and vicinity, a railway station situated at the junction of the 
 Ferrocarril Longitudinal with the Copiapo-Caldera line, where the longitudinal 
 valley joins the transverse valley of the Copiapo River, at the northwest base of the 
 Cerro Bramador, or Singing Mountain; elevation 291 meters. 
 
 Position —Longitude 70° 27' west, latitude 27 0 19' south. 
 
 Observations —Faulting was suspected in this vicinity because the longitudinal 
 valley was regarded as of tectonic origin, but no fault was identified. On the con¬ 
 trary, on ascending to a rock terrace on the west side of the longitudinal, 90 meters 
 above the valley floor and about 3 km. west of Toledo, it was found to represent an 
 
 159 
 
 15 
 
160 
 
 Earthquake Conditions in Chile 
 
 earlier (Pliocene?) valley floor, which could be recognized in shoulders and passes 
 on the slopes of the longitudinal valley from southeast to southwest and also along 
 those of the Copiapo from northwest to northeast. Its slope, as observed with hand- 
 level, was noticeable and toward the west, the coastal block to which it belongs hav¬ 
 ing been tilted in that direction. The continuity of this floor precludes the possibility 
 of faulting along the axis of the longitudinal valley, at least since the river has cut its 
 level. 
 
 Because of the fractured condition of the rock the existence was suspected of a 
 transverse fault of pre-Pliocene or Pliocene age, trending about N. 6o° W. across 
 the rock bench from which the above observations were made and passing southwest 
 of Cerro Bramador into the Copiapo basin, southwest of the city. Its presence was 
 not demonstrated however. (See Plate XXXIV A.) 
 
 Observations on joints in basal complex in rock terrace on west side of longi¬ 
 tudinal valley, 90 meters above the plain: Strike north 62° west magnetic, dip 
 64° north; strike north 25 0 east, dip vertical; strike north 85° east, dip 85° south. 
 Descending from terrace to the plain, joints observed in aplite dike, very clearly 
 defined: Strike north n° east, magnetic, dip 80 west and strike north 6o° west, dip 
 85° north. The former of these two is displaced on the latter about 2 cm. north on the 
 west side. 
 
 QUEBRADA DE PAIPOTE 
 FROM PUQUIOS NORTHEAST TO EL BOLO 
 
 Being a description of a geologic section reconnoitered in the Quebrada de Pai- 
 pote between Puquios, a station at the end of a branch railroad, longitude 69° 53', 
 latitude 27 0 10', elevation 1,238 meters above sea by railroad, and a place called 
 El Bolo, at the mouth of the Quebrada del Hielo, longitude 69° 37', latitude 27 0 07', 
 elevation 2,110 meters by barometer. 
 
 The rocks seen in this section belong chiefly to the Mesozoic, comprising sedi¬ 
 ments of the ages from Rhetic to Neocomian, together with associated eruptive flows 
 and intrusives. They are grouped and identified by Felsch as follows: 
 
 Neocomian: Reddish standstones, shales, and thin-bedded gray limestones, with diabase, 
 
 Upper Jurassic: Dark limestones and calcareous shales, associated with porphyritic breccias 
 and instrusive melaphvres. 
 
 Middle Jurassic: Reddish gray limestones interbedded with red and green shales and sand¬ 
 stones, accompanied by massive flows of labradorite porphry. 
 
 Lower Jurassic: Heavy, gray limestones and calcareous sandstones. 
 
 The western end of the section is in the Lower and Middle Jurassic, the middle 
 is largely in the Neocomian, and the eastern part is again Jurassic. Thus there is a 
 suggestion of synclinal structure, but there are no extensive eastward dips. All the 
 strata dip more or less steeply westward, except for local folds, and are thrust up on 
 a number of faults. The structure is too complex to be untangled during a ride such 
 as we had to make and the following notes indicate only the more conspicuous details. 
 Rhetic conglomerates, sandstones, and coal beds were examined in the Quebrada de 
 Carbon, tributary to the Paipote about 15 kilometers east of Puquios. 
 
Geologic Notes 
 
 161 
 
 Distance 
 east of 
 
 Puquios. ROCKS AND THEIR RELATIONS 
 
 Km. 
 
 o Dark purple and green porphyries (melaphyres?) are intruded into gray (Upper Jurassic?) 
 
 limestones, which had previously been folded. The relations are exposed at Puquios and also I km. 
 farther east at the waterhole, at the mouth of the gorge that leads up to Carrera Pinto. 
 
 i Limestone (Upper Jurassic?) forms cliffs on the southern side of the canyon and is traversed by 
 
 a thrust. (See panoramic view, plate XXXVII A.) 
 
 1.8 The limestone rests on labradorite porphyry. Younger intrusives cut the sediments. 
 
 2.2 Steeply dipping red sandstones (Neocomian?) with black pebbles are here separated from over- 
 
 lying green sandstones by a zone of disturbed strata corresponding to a thrust. Both series are cut 
 by intrusives. 
 
 3.8 At this point limestone is discordantly overlain by labradorite porphyry, which is overthrust upon 
 it. The limestone dips 45 0 to 50° west. 
 
 5.1 Quartzite under sandstone. 
 
 6.2 Red sandstone (Neocomian?) conformably underlies sandstone of last note, indicating that it is 
 not Palaeozoic quartzite, as was suspected, but is a local metamorphic. 
 
 at the canyon level, but rises to vertical dip higher up, against a small thrust. Acid dikes lie in the 
 plane of the thrust, striking north 44° east magnetic and dipping 70° northwest. 
 
 13.7 From the last observation on, the cliffs of the canyon consist chiefly of altered porphyritic brec¬ 
 cias (L’pper Jurassic, Felsch?). At this point red sandstone is overthrust on violet-colored breccia. 
 Strike north 15 0 west, dip 50° west. 
 
 14.8 The breccias appear to form the greater part of the southern wall of the canyon for the last 
 kilometer. The northern wall exhibits a zone of thrusting in the red sandstones and breccias. At 
 this point strata of unlike character form the opposed limbs of a faulted structure demonstrating a 
 thrust of more than 300 meters. (See fig. 11.) 
 
 15.9 Junction of a canyon from the north, the Quebrada de San Andres, with the Paipote. The rocks 
 are red sandstones, extensively intruded by dikes and greatly leached; altered Neocomian? Dip 80 ° 
 to 85° west. 
 
 16.6 The south side of the canyon shows red shale (Middle Jurassic?) forced up to a vertical attitude 
 
 and associated with younger intrusives, but overlying massive labradorite porphyry in apparent 
 conformity (lowest Middle Jurassic?). The labradorite porphyry forms the massive walls of 
 La Puerta, extending about 3 km. eastward up the Paipote. (See Plate XXXVII B.) 
 
 20 Hacienda de La Puerta, located at a spring zone in the Quebrada de Paipote. A group of old 
 adobe houses tucked into the massive porphyry cliffs. 
 
 21 At this point the labradorite porphyry is interbedded with red sandstones and shales, dipping 
 about 25 0 east, but upturned to past the vertical in the canyon walls. (See fig. 11.) 
 
162 
 
 Earthquake Conditions in Chile 
 
 Distance 
 east of 
 Puquios. 
 
 Km. 
 
 24 
 
 24.9 
 
 25-5 
 
 26 to 27.4 
 
 28.5 
 
 29.g to 314 
 
 337 
 
 35 
 
 36 
 
 Here red shale, highly calcareous, conformably underlies the labradorite porphyry, which is a 
 breccia and occurs as a stratified series of flows interbedded with the shale. The breccia may have 
 been submarine. 
 
 Red shale conformably overlying porphyry. The shale is fossiliferous and of Middle Jurassic, 
 Dogger; age according to field determination by Felsch. 
 
 Conglomerate bed, 5 feet thick, containing pebbles of porphyry, with calcareous sandstone in red 
 and green shales. 
 
 In this distance the labradorite porphyry forms an anticlinal arch within which the green and red 
 shales are somewhat complexly folded and faulted. It is apparent that the porphyry was competent 
 to lift enough of the load to give the shales within the arch freer displacement than they would have 
 had otherwise. (See fig. 12.) 
 
 Since the last observation we have passed over a shallow syncline in the labradorite porphyry. At 
 this point the dip is 20° toward the northwest. 
 
 In this stretch we have crossed a low anticline in the red shales and labradorite porphyry (Middle 
 Jurassic, Felsch). 
 
 Since last observation the course is northeast from a fork of the quebrada, along a shallow syn¬ 
 cline. At this point, El Bolo, is the mouth of the Quebrada del Hielo, which issues from a narrow 
 gorge in white to yellow rhyolite or trachyte (Felsch). The latter is a Tertiary (?) intrusive along 
 a fault plane, which marks the boundary between the Middle Jurassic terranes and Tertiary lavas. 
 
 East side of trachyte dike; green tuffs and flows of andesite dip 30° away from it and then flatten 
 out to extend eastward in nearly horizontal position. These are Tertiary by their acid character and 
 undisturbed attitudes. 
 
 In the Quebrada del Hielo. Limestone erratics, 3 feet in diameter, lie on the surface at one point. 
 They exhibit glacial striae, deeply grooved and crossing each other on rounded surfaces, showing 
 that they were transported either by floating ice or by cloudburst from an altitude at which there 
 was a glacier. The Quebrada del Hielo heads in the Cerro Tronquitos, about 20 km. east by south 
 from El Bolo at an altitude of 4,000 to 4,500 meters. This evidence of glaciation thus falls in line 
 with that seen at Potrerillos, q. v. The limestone blocks contain large oysters which suggest Upper 
 Jurassic forms (Felsch). Some of the boulders consist of a peculiar limestone conglomerate with 
 yellow sandstone and shale fragments in a red sandstone matrix. (See Plate LIII B.) 
 
 From the Quebrada del Hielo we returned to La Puerta and the next day to 
 Puquios, reviewing our observations en route. At the Quebrada de Carbon, which 
 enters the Paipote just west of the forks of the Paipote and San Andres, we turned 
 south into the Quebrada de Carbon and followed it up about 2.5 km. to the exposures 
 of coal beds in the Rhetic. 
 
 The Rhetic strata are composed of coarse conglomerate and sandstone, of 
 which the part that is here exposed measures about 120 meters in thickness and car¬ 
 ries three coal beds. The strike is south 45 east and the dip 50° northeast. The for¬ 
 mation continues downward to a great thickness. It is cut by dikes. The coal beds 
 are 3, 5, and 12 feet thick. The thickest is divided by two strata of sandstone into 
 three benches of coal. All the beds are greatly compressed and sheared and are 
 valueless. 
 
 For observations in the Quebrada de Paipote west of Puquios see notes of the 
 ride from Puquios to Chulo, which follow. 
 
Geologic Notes 
 
 163 
 
 QUEBRADA DE PAIPOTE 
 
 FROM PUQUIOS SOUTHWEST TO CHULO 
 
 Observations between Puquios and Chulo riding from Puquios down the Que- 
 brada de Paipote to the railroad junction on the main line at Chulo. For extension 
 of the section eastward see notes of the ride from Puquios to El Bolo, page 160. 
 
 Distance 
 
 from ROCKS AND THEIR RELATIONS 
 
 Puquios. 
 
 At Puquios the rocks are Mesozoic eruptives intruded into folded upper Jurassic limestones which 
 Km. were subsequently overthrust. (See Plate XXXVII A.) 
 
 1.4 Riding south 15 0 west magnetic we here cross a fault on an anticlinal axis striking south 35 0 
 
 west magnetic. The south limb is thrust up over the northern, bringing red shale against labradorite 
 porphyry. 
 
 2.9 From this point the view down the quebrada is nearly along the strike, crossing a gentle syncline 
 
 to the adjacent anticline. Both banks of the valley are of green shale, probably Lias. 
 
 3.6 The valley enters the line of a thrust on the axis, which is marked by a vein of yellow limonite 
 
 that can be seen passing out on the southern side several kilometers ahead. Labradorite porphyry 
 occurs south of the thrust. The quebrada is eroded in the northward dipping limb of the anticline, 
 the dip varying from 30° on the southeast side to xo° on the northwest. 
 
 8.8 The rocks at this point are thin-bedded volcanic breccias with soft lava flows, eroded in conical 
 forms. They belong to a coarse breccia zone that lies above the labradorite porphyry. 
 
 9.8 Kilometer 27 on the railroad. The axial fault noted above can be seen in the canyon wall about 
 
 2 km. distant. The dips indicate a broken anticline. All higher hills show a gentle dip to the south¬ 
 
 east. Strata north of the fault also dip 20° southeast, toward the fault. 
 
 Estacion Venado. Approaching this station Cerro Venado bears south io° west and exhibits the 
 Jurassic strata of the Dogger and Lias horizons dipping gently southeast. 
 
 17.8 Railroad kilometer 19, whence the quebrada trends southwest. 
 
 19. 1 Turned north 67° west magnetic across the Quebrada to examine the rocks in the gullies on the 
 
 northern side. A thrust plane passes through this point of observation bearing north 12 0 east and 
 south 14 0 west magnetic in opposite directions and dipping 70° west. (See fig. 13.) 
 
 19.6 Cliff’s of fawn-colored acid breccia dipping 8o° north. 
 
 20.8 Railroad kilometer 16. The structure is synclinal. 
 
 22.8 Railroad kilometer 14. The strata are sharply turned upward on the west limb. 
 
 29.8 Railroad kilometer 7. Looking southeast to a high point in the range, Cerro Garin, we see a crest 
 of labradorite porphyry forming cliffs over a softer green formation, all dipping southeast. To the 
 north of Cerro Garin the sediments and igneous breccias lie nearly flat, but maintain the southeast¬ 
 ward dip. (See fig. 14.) 
 
 30.8 Railroad kilometer 6. At this point is the contact of greenish sedimentary strata overlying thick- 
 
 bedded brown porphyry breccias, all dipping 15 0 southeast. The bedded porphyry extends past 
 Chulo and forms the walls of the Quebrada all the way to Paipote, some 15 km. They are Mesozoic 
 and probably all Jurassic. 
 
164 
 
 Earthquake Conditions in Chile 
 
 UPPER COPIAPO VALLEY 
 
 PAIPOTE TO PORTO DE CANTAR 1 TO 
 
 Being a description of geologic notes made in riding up the upper Copiapo Val¬ 
 ley from Paipote to La Junta, thence via the Port 0 de La Iglesia to the headwaters of 
 the Rio Manfias, and to the Port 0 de Cantarito. 
 
 Paipote, latitude 27 0 25' south; longitude 70° 12' west; elevation 439 meters, R. R. 
 
 La Junta, latitude 28° 02' south; longitude 70° west; elevation 1,365 meters, map. 
 
 La Iglesia, latitude 28° 13' south; longitude 69° 55' west. 
 
 Port 0 de Cantarito, latitude 28° 36' south; longitude 69° 53' west; elevation 4,106 meters. 
 
 The rocks encountered in the upper Copiapo Valley comprise both sedimentary 
 and igneous classes and range in age from the Paleozoic to the Neocomian. Granites 
 occur at both ends of the section and are regarded as the oldest of the rocks. The 
 Jurassic and Cretaceous terranes represent the horizons which are exposed by the 
 Quebrada de Paipote in their extension along the strike southwestward. The major 
 structural facts are similar in the Quebrada de Paipote and the upper Copiapo Val¬ 
 ley, but there are material local differences, as would be expected in a section of sedi¬ 
 ments alternating with lava flows, sheets and dikes, and traversed by numerous faults. 
 
 Distance 
 
 pJpSe ROCKS AND THEIR RELATIONS 
 
 southward. 
 
 Paipote is at the junction of the Quebrada de Paipote with the upper Copiapo Valley, which 
 immediately widens into the basin of Copiapo. The surrounding rocks are granite and diabase of 
 the Paleozoic series of the coast ranges. 
 
 At Paipote there is a high promontory of rock immediately northwest of the Casa Florida, a 
 ranchhouse. The rock is Paleozoic diabase, which is conspicuously jointed and exhibits three dis¬ 
 tinct joint systems, namely: 
 
 (1) Strike north 82° west; dip 58° south. 
 
 (2) Strike north 8° west; dip 75° west. 
 
 K m . (3) Strike northeast; approximately, dip 55° southeast; irregular. 
 
 1.5 The west bank of the Copiapo exposes a quartzite assigned to the Paleozoic. It is intruded by 
 
 diorite which east of the river also occurs in thick flows interbedded with black limestone. The 
 limestone and porphyry series extends east to Chulo (see notes on the Quebrada de Paipote), dips 
 southeast and comprises Jurassic terranes. The sequence is well exposed in the Quebrada de 
 Melendez, which enters the upper Copiapo Valley from the east 4 km. south of Paipote. 
 
 4 Quebrada de Melendez. In the mouth of the Quebrada, about a kilometer east of the railroad, the 
 
 exposed rock is an altered eruptive of the Paleozoic facies. The cliffs expose a fault contact on 
 which the Paleozoic is overthrust upon the Mesozoic in obvious superposition. The relations are 
 well exposed in the northern spur of Cerro Ladrillos looking northeast, and also toward the south¬ 
 west in Cerro Ojancos. The contact zone is intruded by later igneous rocks and is mineralized. 
 Farther up the Quebrada de Melendez is fossiliferous blue limestone which weathers yellow. The 
 strata dip gently to the southeast and constitute the lower part of a thick series which presumably 
 includes both Jurassic and lower Cretaceous horizons. (See fig. 15.) 
 
 Fig. 15 —Field sketch of thrust in Cerro Ladrillos. 
 
 Totoralillo. From the Quebrada de Melendez to Totoralillo the valley is eroded at a small acute 
 angle to the strike of the Jurassic and Cretaceous limestones and volcanic flows, which dip south¬ 
 eastward on a gentle flexure. Near Totoralillo the western escarpment of the canyon, which is here 
 narrow and bold, exhibits an overthrust, striking north 15 0 east magnetic and dipping 45 0 to 6o° 
 
Geologic Notes 
 
 165 
 
 west. The yellow limestone series (Cretaceous) is duplicated thereby. The lower section extends 
 southward up the valley, but passes over an anticline and dips southeast beyond Totoralillo. 
 
 Pabellon. Between Totoralillo and Pabellon the Cretaceous limestones are sharply folded and 
 somewhat crushed. At the turn in the valley about 2 km. north of Pabellon the strata crossing the 
 canyon expose a bedded flow or sheet of igneous rock between two thick strata of limestone. There 
 is a good deal of crushing in the igneous rock, and the limestone on the northwest is overturned. 
 This is regarded as a fault contact. (See figs. 16A and B.) 
 
 A 
 
 Figs. 16 A and B —Field sketch of Creta¬ 
 ceous limestone and intrusive, section and 
 plan; near Pabellon. 
 
 
 For 5 km. above Pabellon the canyon is cut in dark volcanic rocks identified by Felsch as pyroxene 
 andesite. It is in part a volcanic breccia and is probably early Tertiary. 
 
 From Pabellon a side trip was made to the mines of Chanarcillo. 
 
 Hornito. Hornito is situated near the middle of a section of volcanic flows and breccias assigned 
 to the early Tertiary, which extend from near Pabellon to within about 2 km. of Tres Puentes. In 
 the immediate vicinity of Hornito these volcanic beds are contorted and faulted. The strike changes 
 from north by east to nearly east and west, and the dip varies from vertical to 35° toward the 
 southeast. The rocks are overthrust and the sequence is repeated. (See fig. 1 7 -) 
 
 Tres Puentes. Two km. north of Tres Puentes the very heavily bedded eruptive is greatly sheared 
 and exhibits minor thrusts (kodak). The joints in the eruptive have the following positions: 
 
 Joints 1, north 64° west, dip 8o° southwest, every 2 to 5 feet corresponding to bedding. 
 
 Joints 2, north 52° west, dip 52 0 southwest. 
 
 Joints 3, south 63° west, dip 6o° southeast. 
 
 About 1 km. north of Tres Puentes the early Tertiary eruptives are in contact with a dark, 
 massive altered igneous mass containing much mica, classified by Felsch as diorite and assigned to 
 the Mesozoic. This rock extends south from Tres Puentes to the vicinity of Loros. It exhibits a 
 great deal of crushing and is much altered. 
 
 Loros: From Loros to San Antonio the canyon walls are of diabase assigned to the Cretaceous. 
 
 San Antonio. San Antonio is located on red sandstone and shale of the upper Jurassic, which lie 
 folded in a shallow syncline. A strong dike of “ liparite ” cuts across the valley and exhibits a 
 strongly sheared structure. It appears to have intruded a fault zone and subsequently to have been 
 faulted. In the east wall of the canyon north of San Antonio the red sandstone strata appear to end 
 abruptly above the eruptive breccias and suggest a thrust from the northwest. But since the lava 
 flows and the red sandstones are interbedded it is probable that the contact is one of deposition, at 
 which the strata abut against the end of the flow. 
 
 Quebrada Calquis. At this point calcareous sandstone and limestone strata, assigned to the upper 
 Jura or Tithon on the evidence of fossils, are overthrust by red sandstones of the older Jura. The 
 upper Jurassic strata extend southward to the Estancia Lautaro, and for about a kilometer beyond 
 it. They there overlie dark-green and violet sandstone and conglomerate containing fossil wood, 
 
Earthquake Conditions in Chile 
 
 166 
 
 which is assigned to the Rhetic. The Rhetic dips about 6o° and the Tithon about 30° with a strike 
 of about south 15 0 west. The Rhetic conglomerate is about 100 feet thick and lies upon a great 
 mass of dark lava flows which contain amygdules and exhibit flow structure. They appear to repre¬ 
 sent a submarine volcano. 
 
 La Junta. This point may be considered the head of the Copiapo River, since it is the junction 
 of three streams by which it is formed. The upper course, in a straight line with the canyon below, 
 is called the Rio Manflas, and two large tributaries, the Rio Jorquera and the Rio Pulido, come 
 in from the east. The canyon widens at the junction, but the rivers enter from deep gorges. 
 
 The rock at the junction is a gneissoid granite which is assigned to the Paleozoic. It is com¬ 
 pletely overarched by the volcanics which underlie the conglomerate of supposed Rhetic age. It is 
 possible, however, that the fossil wood on which the age is predicated may belong to the Jurassic 
 and that the volcanic activity occurred in that period. This would seem more consistent with obser¬ 
 vations on the Rhetic elsewhere. 
 
 From La Junta the trail ascends the Manflas a short distance, but turns east from the inaccessible 
 canyon and ascends between the Manflas and the Pulido to the Vegas de la Iglesia. The route lies 
 wholly in dark volcanic lava flows, probably of the lower Jura. The anticline which exposes the 
 Paleozoic at La Junta descends on a vertical dip eastward to a syncline from which the beds rise, 
 dipping 20° to 30° west. The syncline is succeeded by a broad anticline which also assumes a vertical 
 or overturned dip toward the southeast. The strata were identified as lower Jurassic by the occur¬ 
 rence of smooth Pectens and large ammonites. 
 
 Las Vegas de la Iglesia. This is a wild amphitheater lying at the western base of the precipitous 
 Cerro de la Iglesia, a granite mass. The valley is inclosed on the west by a moraine of granite 
 no meters high, which is composed of boulders derived from the Cerro de la Iglesia. The amphi¬ 
 theater thus corresponds with the bed of a local glacier which gathered in the shadow of the great 
 peak. The height of the peak is given as 3,840 meters, and that of the amphitheater is probably about 
 2,600. (See fig. 18.) 
 
 Fig. 18 —Field sketch of bed and moraine of glacierette in 
 Cerro de la Iglesia. 
 
 The moraine rests upon recent or late Tertiary volcanics, which dip east toward the granite and 
 extend west to the Jurassic eruptives upon which they lie. 
 
 The pass of Las Vegas de la Iglesia is located on a line of thrust which traverses the granite and 
 is occupied by Tertiary volcanics. The section may be seen looking north from a point 3 km. south 
 of the pass. The view shows a granite knob west of the pass with Jurassic overlying the granite on 
 its western slope and Tertiary volcanics filling the pass on the east. In this view the volcanics appear 
 to have an anticlinal structure, indicating subsequent disturbance. The thrust lies along the line of 
 outflow of the volcanics and cuts partly across granite north of the Vegas and between granite and 
 Jurassic south of that point. (See fig. 19.) 
 
 W. E. 
 
 Fig. 19 —Field sketch of La Iglesia thrust. 
 
Geologic Notes 
 
 167 
 
 Prom Las Vegas de la Iglesia the trail descends into the upper canyon of the Manflas, partly 
 over Tertiary volcanics and partly over the Jurassic which lies west of the volcanic belt. Where the 
 trail strikes the river near latitude 28° 22' south, 69° 59' west, there are extensive exposures of the 
 red and gray limestones of the middle Jurassic, with many fossils. 
 
 The headwaters of the Manfias, where the river flows northwest, run through Tertiary volcanics 
 as far east as the Porto de Cantarito, east of which high peaks of very precipitous character and 
 gray color resemble the Cerro de la Iglesia and like it probably represent a granite range. 
 
 From the Port 0 de Cantarito the route descends to the northwestern headwaters of the Rio Huasco 
 past Lago Grande, and thence down that stream to Vallenar (see notes which follow). 
 
 VALLEY OF THE RIO HUASCO 
 
 PORTO de CANTARITO TO HUASCO ON THE COAST 
 
 The following notes represent the observations taken in riding from the Port 0 
 de Cantarito southward down the canyon past Laguna Grande to La Pampa in a 
 southwesterly direction and thence in a west-northwesterly course down the Rio 
 Transito and its continuation as the Rio Huasco to the sea. 
 
 In general the section is a repetition of the rocks observed on the upper Rio 
 Copiapo, representing chiefly the Mesozoic horizons, to a point about 5 km. east of 
 Vallenar, where the Paleozoics of the Coast Range begin and from there on form 
 the canyon of the lower valley. 
 
 DETAILS OF OBSERVATIONS; ROCKS AND THEIR RELATIONS 
 
 Laguna Grande is a small lake dammed by a large landslide from a coarse gravel deposit of Pleistocene or 
 Pliocene age, which forms very remarkable cliffs on the east side of the valley. The height of the cliffs was 
 estimated at about 400 meters, and the mass of the formation appeared most unusual. It contained very large 
 boulders such as are characteristic of alluvial fans in regions of cloudbursts, and is probably an alluvial fan 
 deposit, but of an age which antedated the development of the canyon and of the faulting which has accompanied 
 the recent elevation of the Cordillera. As seen from Laguna Grande, this great gravel deposit, elevated high in 
 the range far above any of the agencies by which it could have been formed, is one of the most striking evidences 
 of recent displacement which we observed in the Cordillera. The elevation of Laguna Grande is given as 3,473 
 meters and that of the granite peak east of it as 5,237 meters. The gravel formation is probably more extensive 
 eastward on the slopes of the peak than can be seen from the canyon below. It invited further investigation, but 
 a winter storm prevented. (See Plate XLIX B.) 
 
 At the outlet of Laguna Grande the cemented gravel masses form a chaotic dam over which the stream 
 falls in a cascade and which, geologically speaking, can have but a brief existence. 
 
 To the northwest of the outlet of Laguna Grande the mountains are composed of Tertiary volcanics. The 
 stream appears to run upon a line of faulting similar to that at Las Vegas de la Iglesia. 
 
 Below Laguna Grande to the vicinity of La Pampa the prevailing rock is granite, which exhibits facies 
 ranging from a dark green gabbro to light gray granite with pink and red varieties. The granite is cut by black- 
 dikes of melaphyre. The structure of the granite is gneissoid, the result of shearing which takes a curved attitude 
 rising very steeply from the west with a curve convex upward. Joints which dip about 40° east are of general 
 occurrence, and they are frequently occupied by dikes of the melaphyre. Nearly vertical dikes and others in less 
 systematic positions also occur. The dikes are of a very uniform width and appear to have entered the granite 
 when it was in a state of tension and to have occupied the spaces between the joint blocks. 
 
 From La Pampa westward the sheared granite extends toward El Portillo, about 5 km., where it is suc¬ 
 ceeded by the Jurassic dipping westward. The contact appeared to present a zone of shearing and probable dis¬ 
 placement. The Jurassic extends to El Transito at the mouth of the Quebrada de Chanchoquin, which is a 
 narrow canyon eroded on a distinct thrust. The rocks are assigned to the lower Jurassic and are repeated west of 
 the thrust with an eastern dip, but are presently succeeded by gneiss of the underlying Paleozoic. 
 
 At the Quebrada de Tabaco the Paleozoic is traversed by a thrust which is indicated by the disturbance and 
 shearing of the rocks exposed in the gorge. 
 
 Proceeding west the Paleozoic is overlain by altered sandstones and conglomerates dipping westward. The 
 conglomerate becomes very heavy in the upper western part. The terrane may represent the “ Gomero ” or lower 
 Mesozoic, possibly Rhetic. 
 
 The supposed Rhetic is succeeded by volcanics and sandstones of the Jurassic, which dip nearly vertically 
 near the contact but flatten to a dip of 40° and extend to the junction Transito with the Rio del Carmen at 
 La Junta del Carmen. 
 
 16 
 
168 
 
 Earthquake Conditions in Chile 
 
 At La Junta del Carmen the nearly vertical dip is pushed eastward by a thrust which brings more gently 
 dipping beds of the Jurassic over the Jurassic, that is there is a thrust within the Jurassic terranes. The Jurassic 
 beds are succeeded by a mass of diorite regarded by Felsch as Cretaceous or possibly Tertiary, which extend to 
 Maiten. 
 
 From Maiten to Marmol the rocks are bedded andesites and andesitic tuffs, which for a long distance lie 
 in a flat position, but at Maiten they are turned up vertically and are seen to lie upon limestones of Neocomian(P) 
 age, dipping 50° east. 
 
 At Pedro Leon Gallo the Neocomian limestone is underlain by porphyritic breccias of the upper Jurassic, 
 which extend to the Quebrada del Jilguero on a flat-lying eastern dip. They are locally much crushed and 
 sheared, especially in the vicinity of Pedro Leon Gallo which is on the line of one of the major thrust faults. At the 
 Quebrada del Jilguero the cliff exhibits the effects of recent faulting and displacement in the earthquake of 1922. 
 (See Plate XXII B.) 
 
 The Quebrada del Jilguero is cut in rock only for a short section near its mouth, while higher up its banks 
 are of gravel and its course has been excavated across the wide terrace which borders the Rio Huasco in its 
 course westward across the wide valley that lies between the foothills of the Andes and the Coast Range in this 
 vicinity. The contact between the Jurassic breccias and the Paleozoic lies under this terrace and was not observed. 
 
 SECTION ON THE RIO ELQUI 
 
 Observations made in a trip by train from La Serena to Rivadavia, 70 km., and 
 thence on foot to Monte Grande in the canyon of the Rio Claro. Returning the trip 
 was made from Rivadavia to Vicuna by hand car and thence by train to La Serena. 
 The observations made on the up-trip were checked on the return, and the combined 
 results are given in the notes. 
 
 ROCKS AND THEIR RELATIONS 
 
 Altovalsol: The effects of the earthquake are seen in the slightly cracked houses of frame and adobe construc¬ 
 tion. Throughout the fields the mud walls of tapiales remain standing. The effect of the shock was evi¬ 
 dently very moderate. 
 
 Las Rojas: Between Altovalsol and Las Rojas granite forms the hills and river bed with rapids. It is a massive 
 light gray rock with dark intrusions. At this point there are conspicuous granite hills on the south side of the 
 river and the same rock extends eastward. The stream has worn conspicuous pot holes. 
 
 Pelicana: The point of rocks east of the station consists of dark green even-grained diabase, apparently intruded 
 in the granite. It is greatly jointed and probably Paleozoic. 
 
 Marquesa: Coming from Pelicana the railroad follows an open valley trending north by east. The valley is con¬ 
 tinued in that direction by the Quebrada Marquesa, while the river, coming from the southeast, emerges from 
 a narrow gorge. The latter is cut in bedded Jurassic breccias and lava flows, which dip 35 0 westward toward 
 the granite. The contact of the granite and Jurassic is a fault contact, the granite being upthrust from the 
 west. 
 
 Almendral: From Marquesa to this point the Jurassic breccias dip westward, but here pass over an anticline and 
 dip 20 0 eastward. The massive brown beds of the lava flow are accompanied by thinner strata which may be 
 sediments. 
 
 Gualligaica: The bedded Jurassic flows appear to overlie a diorite which is probably intrusive and younger. The 
 diorite is a large mass extending eastward. 
 
 Tambo: The diorite, which has extended to this point, is in this neighborhood in contact with bedded breccias 
 dipping io° eastward from it. 
 
 Vicuna: Between Tambo and Vicuna there is a broad syncline which at Vicuna is followed by a broad flat anti¬ 
 cline. The rocks are the bedded breccias which we regard as Jurassic. From Vicuna they dip eastward and 
 come to form dark rugged peaks which were covered with snow. 
 
 Durazno: The railroad cuts above Durazno show the greatly jointed breccias covered with river gravel on the 
 terraces. There are many boulders of granite and even the larger ones appear to be thoroughly decayed, 
 indicating an early Pleistocene age for the gravel deposit. 
 
 Arenal: From a point a short distance above Durazno a gneissoid granite of Paleozoic facies forms both walls 
 of the canyon. The structure is similar to that seen on the headwaters of the Huasco above La Pampa. The 
 granite is intruded by andesite of uncertain age, possibly Tertiary. On the east the granite is covered by 
 dark red lava flows and breccias associated with red sandstone, which we regard as Jurassic. They extend to 
 Rivadavia in the higher mountains, but the canyon is in granite. 
 
 Rivadavia: At Rivadavia, at the junction of the Rio Claro with the Rio Turbio, the rock is granite which is over- 
 lain by sediments containing fossils of the Lias and associated with flow breccias, all of which dip west. 
 The Lias is represented by red calcareous sandstone, outcropping on the road south of Rivadavia and extend¬ 
 ing up the Claro Valley on the west side. The strata rise from a nearly flat west dip almost vertically 
 
Geologic Notes 
 
 169 
 
 against the fault, which strikes north 5 0 east and dips 70° west in the heights south of the river. The 
 granite underlies the Lias, which was deposited on a very hilly surface having a relief of at least a hundred 
 meters, so that the thrust sometimes brings Lias against granite as if deposited on it, or granite over Lias in 
 obvious fault contact. Where remnants of the Lias occur east of the fault the strata lie as deposited upon 
 granite, as just above Paignano. The canyon above Paignano is cut in granite at least as far as Monte Grande. 
 
 At Paignano the canyon turns south on granite, and it is possible that there is a fault passing through Monte 
 Grande, but we were unable to proceed as far as that to verify the inference. The valleys of the Rio Claro 
 and the Rio Turbio appear to be eroded in a broad zone of complex thrusts, lying between Paignano on the 
 east and Diaguitas on the west. It corresponds in general position and character to the fault zone encountered 
 on the upper Rio Huasco, and possibly may be represented by the complex overthrusts found in Asientos 
 canyon near Potrerillos, with which it corresponds in strike. 
 
APPENDIX V 
 
 PETROGRAPHIC SKETCH 
 
 BY HENRY S. WASHINGTON 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
PETROGRAPHIC SKETCH 
 
 It was the original intention that the rocks collected by Willis should be described 
 by H. S. Washington, and the general results embodied in an appendix to this 
 volume. This intention, however, was not carried out, and it is now proposed that the 
 results of such a petrographic study shall form the subject of a separate paper, to be 
 published elsewhere, in which all the specimens will be described in detail, and the 
 results of this examination of these Chilean rocks, as in a way representing the Andean 
 and Cordilleran Circum-Pacific igneous rocks, will be contrasted with the Intro- 
 Pacific volcanic lavas. In the meantime, and for this purpose, a dozen chemical 
 analyses of Willis’ specimens were made in the Geophysical Laboratory of the 
 Carnegie Institution of Washington by Miss Mary G. Keyes. As a part of the main 
 paper, and to put them on record as a contribution to our knowledge of the Andean 
 igneous rocks, they are presented here (Table, page 176), with very brief and sketchy 
 descriptions of the petrography of the rocks that were analysed. Some of the speci¬ 
 mens that were studied were not fresh, but they were analysed notwithstanding, for 
 lack of better material. The amounts of CO2 in these cases were not determined, the 
 completion of the analyses being postponed to a future occasion. For this reason the 
 summation of certain of the analyses is very low (as in Nos. 5, 10, 11, and 12), this 
 being noted in the Table. The numbers in parentheses (B. W. 3145, etc.) are those 
 borne by the specimens. The analyses are arranged in the order of decreasing per¬ 
 centage of SiCk. 
 
 PETROGRAPHICAL DESCRIPTIONS 
 
 (1) Granite, Chaharal —Coarse grained; very light, almost white, in color. 
 Composed mostly of alkali feldspar with much quartz, and few small shreds of dark 
 mica. Typical granitic texture shown in thin section. Much more orthoclase than 
 oligoclase: the former mostly untwinned, and the latter with many very fine twinning 
 lamellae, of about the composition AbeAni. The mica is mostly muscovite, but is not 
 well crystallized and is rare. There are very few ore grains. There is some evidence 
 of crushing. 
 
 (2) Biotite granodiorite, Copiapo —Megascopically fine grained, light gray in 
 color: showing small specks of black biotite in mixture of feldspar and quartz. In 
 thin section the quartz shows no inclusions. The feldspar is fresh and not much 
 twinned. It is mostly oligoclase, about AbsAm, many grains with borders of ortho¬ 
 clase. The pale olive-green, not very pleochroic biotite forms irregular shreds. Some 
 small, irregular grains of ore are apparently ilmenitic magnetite, to judge from the 
 somewhat brownish color. The texture is granitic. 
 
 (3) Hyalodacite, Agua Encantada —Small phenocrysts of slightly yellowish 
 white feldspar are scattered through a phaneric, almost black, fine-grained ground- 
 mass of quartz and feldspar, with black mesostasis. Thin sections show some flow- 
 texture. The feldspar phenocrysts are subhedral, many fragmentary. Most of them 
 are of oligoclase, about AbsAm; these show not well developed twinning lamellae. A 
 few fragmentary and anhedral, small quartz phenocrysts. There are some subhedral 
 prismoids of very pale greenish augite, with extinction up to about 40°, with coarse 
 
 173 
 
174 
 
 Earthquake Conditions in Chile 
 
 cleavage. There is no biotite. The few somewhat irregular ore grains are apparently 
 somewhat ilmenitic. The microgroundmass is dusty and pale brownish, with some 
 flow texture around the phenocrysts. It is highly vitreous and the “ dust ” is irre¬ 
 solvable under high powers. 
 
 ( 4 ) Biotite granodiorite, Near Copiapo —Fine grained, phaneric, light gray. 
 Thin sections show typical granitic texture. Very little quartz, in small anhedra. 
 The feldspar is almost all andesine, somewhat twinned, about AbsAiu, some with 
 borders of orthoclase. Very little orthoclase. Some olive-green biotite, in irregular 
 grains and thick tables, which occasionally are poikilitic about the plagioclase. 
 Irregular grains of somewhat brownish, ilmenitic magnetite are not very abundant. 
 
 (5) Biotite granodiorite, Cortadera Station —Medium grained, black biotite, 
 with very slightly yellowish feldspar and some quartz. In thin section the texture is 
 typically granitic. The amount of quartz is apparently less than that indicated in 
 the norm. The abundant andesine, about AbiAm, is much altered with the production 
 of calcite. There is little orthoclase. There is considerable olive-green biotite in very 
 ragged individuals. The not very abundant, irregular ore grains are of the pure black 
 of magnetite, so that the TiOa is probably mostly in the biotite, which is darker than 
 in the preceding specimens. 
 
 ( 6 ) Hornblende hyalodacite, Cerro Doha Inez —Small prisms of black horn¬ 
 blende, with many phenocrysts of white feldspar, but none of quartz, are scattered 
 through a very light gray, almost white, groundmass. The thin sections show many 
 sharp subhedral phenocrysts of andesine, somewhat twinned, about AbaAm, with 
 fewer of subhedral orthoclase. No quartz is visible. The small, euhedral prisms of 
 olive-green hornblende are not abundant, and there is an occasional small table of 
 green biotite. The not abundant, irregular ore grains are black, so that much of the 
 rather large amount of TiCb is probably in the hornblende. The microgroundmass is 
 pale gray and slightly “ dusty ” (the “ dust ” being irresolvable under high powers). 
 It is very vitreous but there is no evidence of flow. 
 
 (?) Augite andesite, Qucbrada Carrizo —The highly porphyritic lava shows 
 very abundant phenocrysts of slightly yellowish feldspar, that are mostly squarish 
 and equant in all sides of the specimen. These are mostly about 2 111m. in diameter. 
 There are very few small and inconspicuous prisms of black augite. The groundmass 
 is very fine grained and pale brownish gray, without evidence of flow texture. In 
 thin section the rock appears to be holocrystalline. The feldspar phenocrysts in thin 
 section are not very well defined, and show little twinning. They are mostly ande¬ 
 sine, about AbsAni. The rather abundant olive-green augite forms subhedral 
 prismoids, which are without inclusions except for a few small ore grains near the 
 borders. The few small (0.02 to 0.10 mm.), irregular ore grains are apparently some¬ 
 what ilmenitic. The colorless microgroundmass is apparently holocrystalline, very 
 fine grained and made up mostly of feldspar that is evidently somewhat more albitic 
 than the phenocrysts, with possibly a little quartz. There is no flow texture. 
 
 (8) Diabase, Pueblo Hundido- —This shows some small, tabular phenocrysts of 
 whitish feldspar, in a very fine-grained or aphanitic, slightly brownish-black ground- 
 mass. In thin section the feldspar phenocrysts are seen to be tabular, not well twinned, 
 
Petrographic Sketch 
 
 175 
 
 of about the composition AbsAm. They are not very fresh. The general microground- 
 mass shows a subophitic texture, made up of small laths of anclesine, with anhedral 
 olive-green augite that is more or less interstitial between the feldspar tables. There 
 are a few small anhedra of quartz. The rather large and irregular grains of ore are 
 brownish and decidedly ilmenitic, and some very small and slender prisms of apatite 
 are present. 
 
 (p) Diabase, Aguada Algarroita —The rock is very fine grained, dense, and 
 aphyric, except for rare and small phenocrysts of black augite. The general color is 
 slightly brownish black, but appears dark gray under the lens. The thin sections are 
 rather unsatisfactory. There are a few phenocrysts of colorless augite and many 
 small prismoids of the same mineral, which must be a diopsicle, to judge from the 
 norm. These, and a few small grains of olivine, are embedded in an indefinite, appar¬ 
 ently feldspathic base. There are no definite feldspar phenocrysts, but a few very 
 small, twinned tables of andesine are seen here and there. The not very abundant ore 
 grains are decidedly ilmenitic. The rock, as a whole, seems to be somewhat altered. 
 
 ( 10 ) Labradorite porphyry, Rio Manftas —The specimen shows many tabular 
 phenocrysts of glassy plagioclase (up to i cm. long and 0.2 cm. wide), in a dark- 
 brownish, fine-grained groundmass. In thin section the euhedral tabular feldspar 
 phenocrysts show well-developed twinning lamellae. They are of about the composi¬ 
 tion AbiAm, and are very fresh. There are no phenocrysts of augite to be seen in the 
 sections. In the microgroundmass are many small (up to 0.2 cm. long) laths of feld¬ 
 spar, of about the composition Ab2Am, that are little twinned. There are a few small, 
 indefinite anhedra of colorless pyroxene, and much dirty, dark reddish-brown and 
 opaque mesotasis interstitial between the small feldspar laths. Small scales and specks 
 of red transparent hematite are present. The rock is evidently not fresh, as is also 
 shown by the large amount of CO2 found on analysis: this existing apparently in cal- 
 cite derived from diopside in the opaque mesostasis, and not visible under the micro¬ 
 scope. Indeed, the rock is so altered that it would not have been analysed but for the 
 fact that the specimen is representative of a type that seems to be fairly abundant in 
 the region. 
 
 (11) Orthoclase diabase (?). Cortadera Station. —The rock is black, and shows 
 a few very small phenocrysts of feldspar, and still fewer of yellow olivine, in a dense, 
 finely grained groundmass. The microscopic study was very unsatisfactory. The 
 few sharply euhedral feldspar phenocrysts are of orthoclase, which is untwinned and 
 not very fresh. The few small phenocrystic grains of olivine are fresh. Thin sections 
 show that the rock is made up largely of colorless or pale yellowish pyroxene in ragged 
 prismoids, with many small subhedral mierophenocrysts of plagioclase, with much 
 interstitial, indefinite, colorless, birefringent material, of low refractive index, that 
 may be in part tbe nephelite shown in the norm, and in part some of the orthoclase. 
 There may be a little glass present, but no ore grains are visible under the microscope. 
 On the whole, it must be confessed that the rock, both modally and chemically, is a 
 puzzling one, and that the bestowal of an appropriate name is difficult. The name 
 selected here must be regarded as provisional and subject to further and more 
 detailed study. 
 
176 
 
 Earthquake Conditions in Chile 
 
 ( 12 ) Diabase (?). Quebrada Paipote —This is a medium gray, densely fine¬ 
 grained aphanitic rock, with no phenocrysts. The thin sections show that the rock 
 is composed largely of colorless or pale yellowish subhedrally prismoidal and some¬ 
 what felted augite, with small subhedral microphenocrysts of plagioclase, that has 
 been much decomposed with the production of calcite. There are many small (o.oi to 
 0.03 mm.), highly euhedral and mostly octahedral grains of ore, dark brownish in 
 color and evidently very ilmenitic. The rock is obviously much altered. 
 
 Analyses of rocks from Atacama, Chile 
 
 (Mary G. Keyes, analyst) 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 11 
 
 12 
 
 Si 0 2 
 
 76.71 
 
 65.01 
 
 64.83 
 
 61.96 
 
 61.00 
 
 60.03 
 
 58.45 
 
 54-76 
 
 53-25 
 
 52.64 
 
 50.17 
 
 48.80 
 
 AljOri 
 
 12.61 
 
 15.40 
 
 14.90 
 
 16.63 
 
 15-35 
 
 17.29 
 
 16.31 
 
 12.51 
 
 17-85 
 
 15-95 
 
 18.75 
 
 15-33 
 
 Fe 2 0 ., 
 
 0.30 
 
 1.62 
 
 1.46 
 
 2.78 
 
 1.70 
 
 i- 5 1 
 
 2.09 
 
 4.60 
 
 0.64 
 
 6.40 
 
 2-93 
 
 2.83 
 
 FeO 
 
 0.97 
 
 2.49 
 
 2.06 
 
 2.72 
 
 346 
 
 2.62 
 
 2.91 
 
 7.88 
 
 2.92 
 
 i. 5 i 
 
 4-56 
 
 4 - 7 i 
 
 MgO 
 
 0.15 
 
 1.29 
 
 1.60 
 
 2.02 
 
 2.32 
 
 2-43 
 
 3-26 
 
 2-77 
 
 5 - 4 i 
 
 1-74 
 
 5-04 
 
 5-57 
 
 CaO 
 
 0.82 
 
 4-25 
 
 3-79 
 
 6.06 
 
 443 
 
 5-97 
 
 5 -i 3 
 
 5-76 
 
 10.96 
 
 7.82 
 
 3 - 9 i 
 
 7-34 
 
 Na *0 
 
 4.42 
 
 4.68 
 
 3-8o 
 
 4.29 
 
 2.98 
 
 4.11 
 
 4.80 
 
 3.85 
 
 4-38 
 
 4-63 
 
 3-42 
 
 3-33 
 
 k 2 o 
 
 2.44 
 
 2.52 
 
 3-35 
 
 i -39 
 
 3 -ii 
 
 1.72 
 
 2-79 
 
 2.50 
 
 0.72 
 
 1.27 
 
 6.64 
 
 2.06 
 
 h 2 o+ 
 
 0.51 
 
 0.63 
 
 1.60 
 
 0-57 
 
 1.49 
 
 1.00 
 
 1.14 
 
 1.26 
 
 1.05 
 
 0.92 
 
 0-95 
 
 2.80 
 
 FLO— 
 
 0.10 
 
 0.06 
 
 0.24 
 
 0.19 
 
 0.12 
 
 0.08 
 
 0.17 
 
 0.14 
 
 0.32 
 
 0.36 
 
 0.03 
 
 0.18 
 
 C 0 2 
 
 . . . 
 
 
 
 
 p. 11. d. 
 
 
 ... 
 
 ... 
 
 . . . 
 
 p. n. d. 
 
 p. n. d. 
 
 p. n. d. 
 
 TiOa 
 
 1-25 
 
 2.12 
 
 1.63 
 
 1-57 
 
 1.67 
 
 2.74 
 
 2.46 
 
 3.02 
 
 2.72 
 
 2.56 
 
 2.65 
 
 2.92 
 
 P 2 O 0 
 
 0.04 
 
 0.21 
 
 0.19 
 
 0.17 
 
 0.17 
 
 0.24 
 
 0.42 
 
 0.58 
 
 0.05 
 
 0.26 
 
 0.08 
 
 0.19 
 
 MnO 
 
 0.06 
 
 0.09 
 
 0.05 
 
 0.05 
 
 0.02 
 
 0.05 
 
 0.08 
 
 0.10 
 
 0.07 
 
 0.09 
 
 0.07 
 
 0.06 
 
 
 100.38 
 
 100.37 
 
 99-50 
 
 100.40 
 
 97.82* 
 
 99-79 
 
 100.01 
 
 99-73 
 
 100.34 
 
 96.15* 
 
 99.20* 
 
 96.12* 
 
 
 
 
 * 
 
 Low summation due to non-determination of C 0 2 . 
 
 
 
 
 
 
 
 
 
 
 
 Norms 
 
 
 
 
 
 
 
 
 I * 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 iof 
 
 II 
 
 12 
 
 Q 
 
 38.46 
 
 17.40 
 
 20.70 
 
 17.64 
 
 18.96 
 
 15.00 
 
 6.96 
 
 8.52 
 
 
 6.24 
 
 
 0-54 
 
 Or 
 
 14.46 
 
 15.01 
 
 20.02 
 
 8-34 
 
 18.35 
 
 10.01 
 
 16.68 
 
 15.01 
 
 3-89 
 
 7.78 
 
 38.92 
 
 12.23 
 
 Ab 
 
 39-30 
 
 39-82 
 
 31.96 
 
 36.15 
 
 25.15 
 
 34-58 
 
 40.35 
 
 32-49 
 
 37.20 
 
 38.77 
 
 15.46 
 
 27-77 
 
 An 
 
 389 
 
 13-34 
 
 13.62 
 
 21.96 
 
 19.18 
 
 23.91 
 
 H -73 
 
 9-45 
 
 26.97 
 
 19.18 
 
 16.40 
 
 20.85 
 
 Ne 
 
 . . . 
 
 . . . 
 
 . . . 
 
 . . . 
 
 • . . 
 
 . . . 
 
 . . . 
 
 . . . 
 
 . . . 
 
 • . • 
 
 7.24 
 
 • . . 
 
 Di 
 
 
 6.05 
 
 3-46 
 
 5-62 
 
 i -54 
 
 303 
 
 6.05 
 
 12.80 
 
 21-44 
 
 9-50 
 
 2.41 
 
 11.58 
 
 Hy 
 
 0.40 
 
 0.40 
 
 2.40 
 
 2.50 
 
 6.65 
 
 4.70 
 
 5-40 
 
 6.40 
 
 1.70 
 
 . . . 
 
 . . . 
 
 10.06 
 
 01 
 
 . . . 
 
 . . . 
 
 . . . 
 
 . . • 
 
 . . . 
 
 . . . 
 
 • . • 
 
 . . . 
 
 1-57 
 
 • . • 
 
 9-34 
 
 ... 
 
 Mt 
 
 • • • 
 
 2.32 
 
 2.09 
 
 3-94 
 
 2-55 
 
 0.46 
 
 2.32 
 
 6-73 
 
 0-93 
 
 . . . 
 
 4.18 
 
 4.18 
 
 11 
 
 2.28 
 
 3-95 
 
 3-04 
 
 3-04 
 
 3-19 
 
 5 -i 7 
 
 4.71 
 
 5-78 
 
 S-I 7 
 
 3-19 
 
 5-17 
 
 5-47 
 
 Hra 
 
 0.32 
 
 
 . . . 
 
 . . • 
 
 • . . 
 
 1.12 
 
 0.48 
 
 . . . 
 
 . . . 
 
 6.40 
 
 . . . 
 
 • . . 
 
 Ap 
 
 
 0-34 
 
 0-34 
 
 0-34 
 
 0-34 
 
 0.67 
 
 1.01 
 
 i -34 
 
 
 0.67 
 
 
 0-34 
 
 
 
 
 
 * Includes C 0.92. 
 
 f Includes Ru 0.90, Wo 2.20. 
 
 
 
 
 
 1. (B. W. 3145 ). 
 
 Granite, 1.3(4).1(2).4. 
 
 Chaharal, 7. (B. W. 3182). 
 
 Andesite, II."5.2".4. Quebrada 
 
 South side of bay, near Barquito. 
 
 
 
 Carrizo, 50 kms. N of Potrerillos. 
 
 
 2. (B. W. 3119) 
 
 Granodiorite, " 
 
 II.4.2.4. 
 
 Copiapo, 8. (B. W. 3144) 
 
 Diabase, II".4(5).2.4. 
 
 Pueblo 
 
 Hill near R. R. station. 
 
 
 
 
 Hundido, Near Empalme, Km. 39, Chaharal 
 
 3. (B. W. 3146). Hyalodacite, 
 
 I (II).4.2".(3)4. 
 
 R. R., Coast Range. 
 
 
 
 
 Aguada Encantada 
 
 60 kms. N by 
 
 E from 9. (B. W. 3112). 
 
 Diabase, II.5.3."5. Near Aguada 
 
 Potrerillos. 
 
 
 
 
 
 
 Algarroita, Vallenar. 
 
 
 
 
 4. (B. W. 3 I 34 )- 
 
 Granodiorite, (1)11.4.3.4 
 
 '. 6 kms. 10. (B. W. 3142). 
 
 Labradorite porphyry, II."5.3.4". 
 
 SW of Copiapo. 
 
 
 
 
 
 El Tolar, Rio Manfias. 
 
 
 
 5. (B. W. 3147) 
 
 . Granodiorite, 
 
 ( 1 ) 11 - 4 - 3 - 3 " Cor 
 
 II. (B.W. 3 I 63 ). 
 
 Orthoclase diabase (?), II.5".2".3. 
 
 tadera Station, Quebrada de Asientos, Potre 
 
 - 
 
 Cortadera Station, 
 
 Quebrada de Asientos, 
 
 rillos R. R 
 
 
 
 
 
 
 Potrerillos R. R. 
 
 
 
 
 6 . (B. W. 3137) 
 
 Hyalodacite, (I)II.4".3.4. Cerro 12. (B. W. 5150). 
 
 Diabase (?) altered, II".5.3.4. 
 
 Dona Inez Volcano, 50 kms. NE of Potrerillos. 
 
 La Puerta, Quebrada Paipote. 
 
 
 
INDEX 
 
 Abandonment of homes.13, 17 
 
 Acceleration .29, 46-48 
 
 Acknowledgments .1-3, 73, 80 
 
 Alaska, comparison of Atacama with. 7 
 
 Analyses, chemical, of rocks... 127, 128, 129, 130, 133 
 
 Andes, character of. 3 
 
 Andesite .155, 174 
 
 Area of terremoto of November 10, 1922.13, 29 
 
 124, 171 
 
 Animals, behavior of. 31 
 
 Atacama, dynamic history of.52-67 
 
 earthquake history of.15-39 
 
 geology of . 151-169 
 
 rocks of ..51, 153-156, 173-176 
 
 Basalt, San Ambrosio. 132 
 
 Bowman, Isaiah, cited.54, 85, 91 
 
 Byerly, Perry, report on seismograms by.I 37 -I 39 
 
 Caldera, earthquake at.34, 143 
 
 Calera valley, origin of. 87 
 
 Caliche, use of term. no 
 
 California, comparison of, with Atacama.7, n, 43 
 
 68-70, 75 
 
 Canyon development, epoch of.91-93 
 
 Carnegie Institution of Washington.1, 3 
 
 Chanaral .12, 35, 143 
 
 Chanarcillo, mines at.89, 95 
 
 Chemical analyses of rocks.. 127, 128, 129, 130, 133, 176 
 
 Chile, type of earthquakes in. 74 
 
 Chuquicamata, copper mine at.80-82 
 
 structural conditions at.79-82 
 
 Climate .115, 119 
 
 Construction of buildings, influence of... .10-13, 17, 
 
 20-23, 30-39, 45-48, 143-147 
 
 Copiapo, earthquakes at.n, 13-23, 29, 35, 144 
 
 Copper, occurrence of. 82 
 
 Coquimbo .8, 103, 117 
 
 earthquakes at .15, 18, 20, 31 
 
 Coquimbo Bay, geology on.101-116 
 
 Cordillera, uplift of.64, 92 
 
 Cretaceous period . 62 
 
 Crust, stability of the.54, 55, 57 
 
 Dacite .173, 174 
 
 Damage to buildings, statistics of.22, 23 
 
 Darwin, Charles, cited.17, 94, 103-106 
 
 Descriptions of earthquakes.14-48 
 
 Diabase .51, 61, 174, 175, 176 
 
 “ Earth movement,” use of term. 26 
 
 Earthquake, antecedents of, November 10, 1922...26-28 
 
 area of .13, 29, 124, 151 
 
 description of .8, 12, 26-48, 143-147 
 
 direction of .44, 143-147, 151 
 
 epicenter of .44, 137 
 
 experiences in .29-39 
 
 origin of .28, 45 
 
 seismograms of.137-139 
 
 Earthquake action, hypothesis of.70-75 
 
 Earthquake, Chilean, type of. 74 
 
 Earthquakes, mechanism of.68-82 
 
 “ Earthquiver,” use of term. 26 
 
 Epicenter .45, 137, 138 
 
 Faults, direction of .152, 156, 160 
 
 influence of .9-11, 28, 71 
 
 Faulting, evidence of.41, 68-73, 151, 156 
 
 Felsch, Dr. Johannes .2, 51, 73, 74 
 
 report on geology by.151-156 
 
 Field sketches .161-166 
 
 Fossils, occurrence of....52, 104, 105, 115, 117, 118, 153 
 
 Freirina, earthquake at.33, 34, 145 
 
 Fringing gravels, use of term.95, 97 
 
 Fruit dish, movement of.151, 152 
 
 Furniture, overturning of.30-39, 143-147 
 
 Geologic notes .’.159-169 
 
 Geology of Atacama...151-169 
 
 Glaciation, evidences of.98-100, 112, 162 
 
 Granite, intrusion of .54, 59, 60, 80, 102 
 
 petrography of . 173 
 
 source of . 60 
 
 Granodiorite, petrography of.173, 174 
 
 Gravel deposits . 93 
 
 Ground, influence of.. 10-13, 21, 23, 29-39, 43 , 44 , I 43 -I 47 
 
 Hall, Capt. Basil, cited. 16 
 
 Heat, generation of. 57 , 59 
 
 History, earthquake, of Atacama.14-39 
 
 Huasco .10, 34, 145 
 
 Hyalodacite, petrography of.173, 174 
 
 Hypothesis of earthquake action.70-75 
 
 Intensities, distribution of.13, 42-45, 141-147 
 
 Isostatic adjustments . 56 
 
 Jordan, Eric, report on fossils by.117-119 
 
 Juan Fernandez Islands, rocks of.127, 129, 131 
 
 Jurassic period . 62 
 
 Keyes, Mary G., analyses by.173, 176 
 
 Labradorite porphyry .51, 62, 175 
 
 La Serena.8, 14, 15, 18, 20, 29-31, 147 
 
 Level, changes of. 53 
 
 Lightning .30, 31, 34, 38 
 
 Lindgren, W., cited.76, 80, 82 
 
 Liparite .51, 155, 165 
 
 Lobsters, destruction of. 122 
 
 Macelwane, J. B., report on seismograms by. ... 137-139 
 
 Mantling gravels, use of term. 95 
 
 Maremotos, see Sea, movement of 
 
 Matureland, Tertiary .85-91 
 
 use of term. 85 
 
 Mesozoic activity .61-63 
 
 horizons . 154 
 
 Mines, effects on.23, 38 
 
 Montessus de Ballore, death of . 2 
 
 cited .14, 15, 19, 20 
 
 Monuments, effects on.39-41 
 
 Nephelite basanite . 127 
 
 Nitrate basins .89, 90 
 
 Noise, see sounds 
 
 Notes, geologic .159-169 
 
 Ocean, movement of.17-19, 24, 31, 34, 35 
 
 Origin of earthquakes.26, 45 
 
 Orthoclase diabase . 175 
 
 Overthrusts .3, 65, 75 , 76, 81, 155, 156, 164 
 
 Pahoehoe lava . 127 
 
 Paipote .160, 163, 164 
 
 Paleozoic activities .5 2 -6 i, 153 
 
 Peat .11, 12 
 
 Peneplain, misuse of term. 84 
 
 Petrography of Atacama rocks.173-176 
 
 177 
 
178 
 
 Index 
 
 Petrology of San Felix rocks.125-133 
 
 Physiographic interpretation .83-100 
 
 Post-Cretaceous Time, events of.83-116 
 
 Potrcrillos .12, 39, 73, 75, 90, 143 
 
 copper mines at. 73 , 90 
 
 Pressure, effect of.55-57 
 
 Puquios .38, 143. 160-163 
 
 Pyroxene porphyries . 154 
 
 Quartz diorite . 155 
 
 Quartz porphyry . 154 
 
 Questionnaires .29-39, 142 
 
 River capture .91, 92 
 
 Rocks of Atacama .51, 152-155, 173-176 
 
 sequence of .5L 64, 152-155 
 
 San Felix and San Ambrosio, geology of.120-124 
 
 petrology of ...125-133 
 
 Sea, movements of .17-19- 24, 31, 34, 35 
 
 Seismograms of earthquake.137-139 
 
 Seismological Society of America. 1 
 
 Sequence of igneous rocks.51, 64, 152-155 
 
 Sierra Nevada of California. 68 
 
 Sierra Vera, Dr. Luis .3, 20, 21, 29, 44, 141 
 
 report by .141-147 
 
 Silver, production at Chanarcillo. 89 
 
 Sky, appearance of.31, 32, 37, 39 
 
 Sounds during earthquake.16, 18, 29-39, 143-147 
 
 Subsoil, influence of, see ground 
 
 Tapiales .22, 25, 29, 32, 45-48 
 
 Temblor, definition of. 26 
 
 Temperature of sea. 122 
 
 Terraces .3, 103-117 
 
 Terremoto, definition of. 26 
 
 see earthquakes 
 
 Tertiary activities .63-67 
 
 Thrust-planes .10, 28, 65, 73, 74, 161, 163-165 
 
 Tokyo, earthquake at. 29 
 
 Trachyte .51, 125, 155 
 
 Tuff . 129 
 
 Vallenar .9, 13, 15, 17, 25, 31-33, 146, 147 
 
 Velocity of earthquake waves. 17 
 
 Volcanoes, Andean . 85 
 
 non-occurrence of. 51 
 
 Washington, H. S., petrology of San Felix.... 125-133 
 petrography of Atacama rocks. 
 
 I 73 'i 76 
 
 Waves, velocity of. 17 
 
 Wells, behavior of water in. 24 
 
 Willis, Bailey, cited .61, 86, 120-124 
 
 geologic notes by.159-169 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 t 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXXII 
 
 ■ 
 
 A. Salaverre, Peru. A landing on northwest coast of Peru in lea of a small promontory. This is a characteristic west coast port of South America, which is poor in harbors. Steep rise of mountain is an effect of recent w 
 
 arping and faulting. Light-colored areas are sand dunes which are here blown up to a height of 
 
 3,000 feet. 
 
 —- *■ 
 
 -» v ‘«* J*r 
 ■»: - ' 
 
 - ... ■■ . WWWfcMNBh—^ _ 
 
 B. Clopiapo. Panoramic view from bride., co„pri,i„ 8 sweep from northeast to .ooth.es, and sh„wi„ g marsh,- character river bed. Wa„ a,o„ S river bounds area tha, ha, been hiied i„ and which maximum destruction occurred. 
 
 mV* 
 
 SI A 
 
 • •* - . ‘ - . d At A 
 

Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXXI 
 
 A. Copiapo. The Capella de Candelaria, an adobe chapel more than ioo years old. which has survived repeated earthquakes. Its adobe walls are tied together by iron rods which go through from side to side and are fastened with key plates. The tower is a very light construction with wood frame. On right is a new church built in 1923. collapse of roof of old chapel having rendered it unfit for service. 
 
 B. Copiapo. Plaza cf Juan Godoy. Houses adjoining the plaza on both sides and the church escaped serious damage to their external walls, but interior plastering was generally destroyed. Foundation material is of gravel and construction of buildings is superior to that of most houses in the city. Block of adobe houses on right was built after earthquake in 1819. at a time when necessity for good workmanship was appreciated. 
 
Plate LXXIV 
 
 Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 I. S 1 ? Ambrosio. 
 
 El Bass demorando al N, 65? 0, distancia 1 mill a 
 
 I. S° Ambrosio 
 
 El centro de la islo demorando al S, distante de tierra 
 
 Cerfc* s 
 
 Levantado por la Oficialidad de la Goleta “Covadonga 
 al man do del Cap 1 . 1 RAMON VIDAL GORMAZ, 
 en Octixbre de 1874 
 
 conchuela 
 
 SUN DA EN METROS, a., arena 
 
 in a. 
 
 ESCALA DE 
 
 I. S 1 ? Ambrosio 
 
 3 Kilonulrvi 
 
 Morro JLmxirillo 
 
 tsoo 
 
 ]. Gonzales 
 
 -Escala de tree kilometros 
 
 1 milla > 
 
 N.18?E 
 
 Visla del Grupo de S n Felix 1 S n Ambrosio, distante de S a Ambrosio 5 millas 
 
 Ocrible 
 
 10 cables 
 
 Santiago de Chile,'. PublieaiLo de on den del Serwr^Alifiuitro dp nwj'irw, i bcyo la di rpcc/on de la Ofieiruis hidroy rafica,, enJLnaro de 1875. 
 
 Ajente en Valparaiso ^du*</ueto KIEL, CalLe de. Cochrane, JV? 91 , 
 
 CHART OF THE ISLAND OF SAN AMBROSIO PREPARED BY THE COVADONGA EXPEDITION, CAPTAIN RAMON VIDAL GORMAZ, IN CHARGE, 1874 
 
 Facsimile of the official publication by the Minister of the Marine. 1875 
 

 
 
 
 0 
 
 
 
 
 
 
 
 
 
 -• 
 
Plate LXXIII 
 
 Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 I ^C-'Ana raf 
 
 
 ) } 
 
 a 495 V-v c&iSJ? / 
 
 4576, 
 
 C Collado 
 
 Isla Pal 
 
 j, 
 
 CtfisSsgir .• 
 
 (C Indio Muert£^30^ 
 
 - A -Ay CgstiRc. 
 
 Chanaral; C\PoPtozuelo ) 
 
 ■9 ' i ’ Blapco 1 /, 
 
 ideninJei 
 
 2304 
 
 4 / | / 
 
 l P ; ° ,)(*&$&£**“*t r'&o 
 ktaN 
 
 . "t3 \ .C.JuricalrtoN \ 
 
 *>tS_ \W; ^50O O !L. 
 
 x/z C //,, e-._5 (J 
 
 MJN-brW&KA <<• S=l»«f L^fC. Carmen^ . 
 
 APAy', 
 
 (PfeceTe^., i^Millonaris . V^S 
 
 ^>Hcpgreaso / V'^. ; 
 
 ''vS^La^Animasj 
 
 604 / 
 
 , /Puerto dt’ ChaJ&arz 
 
 / * "rw; J 
 
 *dnta /nfielesC^w' 1 
 
 YSZ Bern 
 
 '993 / 
 
 £ -4400> 
 
 ^[ejioclio*' 
 
 • )K^ £ 
 
 l^lote.ySS 
 
 
 Purit.a Brava' /. 
 
 /Portrdel 
 
 Sa/rtre 
 
 'Teniefite Serrano 
 
 '. IeI Leonid) 
 
 ,-C"cle la Qh 
 
 -X ,4240 V I 
 
 .GiSan'ffugufci 
 
 Mocobi 
 
 ' v^Tm&a^-de [bafarsjiyl [_ 
 
 §S iOr „ 
 
 , A 559 P 
 
 v — / 
 
 ■V Anfeqstur 
 Mercediias^ 1,6 
 
 Blanca 
 
 U C Car^chapa/np// 
 
 AT5260 / ' 4400 1 // f 
 
 * 'Van/fa\ 
 
 C del Chivdto 
 
 ■ ' 2276\,/*> •,, 
 
 -Cajoncito 
 
 ■£ Wheelwright 
 
 ^Unive 
 
 lela BlaiVca 
 
 Caleta, Pbisyito 
 
 ( 
 
 I ; fi. tC. Hermitano 
 eelwrijtotv-^ 6 * 40 ^ CL. 
 
 LfO* 5 ®f° A6000 58591 
 
 V^fPena BlanW 0 
 
 ^ ^ x 5 o°° 
 
 X . .e.00- . 
 
 Ag.Sdik;o$a^ 
 
 d SfdLoi 
 
 *p- ^5110 
 A4970 
 
 /b C? Nev? 
 
 ( de Juncalito 
 
 /'too'' ,/y 
 
 //£>/ 
 
 Punta Cab* za W Vaca 
 
 ^C.Bfinderita 
 
 Chimb r 
 
 Colorado 
 
 -£ df; Piedrp Pomei 
 
 46 ~. 
 
 C A5760 
 
 <a F's)>eranza Y 
 
 f Afartciaigc 
 
 Port Co/oodb 
 
 Jesctibriclor 
 
 San Af 
 
 Trey Cruces /(f M* 
 
 .’■ -so 0 Jy : r 
 
 l os TPes' 
 
 A6Q3ft 
 
 '61001, 
 
 \ // PuertC <le Ca/! 
 
 I // Cdtetc/ aH&illt 
 
 /; / // m 
 
 /Pu/nta Morroj/sv/y/c: 
 
 nrac^Slf'P° rt C.DK 
 
 u'M Gat0 -TUp 
 
 S 'C. ttedanozo Ji^ 
 
 
 jdtfenfi nu~ rv. 
 
 lifrO ®£A fRA/LE 
 C. 'N^I'o de'Plaza/ 
 
 ^ ii eo '-•i 
 
 I 540QA 
 
 Llano •/ 
 
 'de i 
 
 □ampa^ 
 
 'C. Ca\Terfnera 
 
 [Pa y o 'de Ires duel 
 Vyi o. Toro Mherx 
 
 Bahsui t Cm>xaf.o \ 
 
 { C Puerto Vibjo 
 
 Caja Chica V/J, 
 | Punti uaHas' -'L 
 
 | Ga n,gws ^ , -rjo# 
 
 ^k&zfrx "‘Wt-yif ■£ p A ..^ / 
 i; v ^sSPlS^S^ 
 
 / : -■] 
 
 , / V ' 1 ' /r t r’d3HhW ^de la Lag. 
 
 f j ' 
 
 5 “ij)<Qp^4 /ro,*rt» : ' ' J-A 
 
 '■?&* 1 /c.dei c»to /</ 
 
 xrttRCiu. v ' 
 
 ^C.Monarde: 
 
 ! ) ['C 
 
 u/FeC^tw^^ 
 
 Pinita IWf;i 
 
 5 ot£ de Votkrtisch&f'todtK \ 
 'orp.'/de Valle Ancho lSi/r\ \ 
 
 \t\\ s 
 
 rvr ;r? '; fe 
 
 Llano 
 
 ‘s<4f s \ 
 
 'Martinez,', 
 
 Punta Barra iquill 
 
 ‘XV 7 A°n ^WS-h>JP£\ 5 
 
 PH 
 
 [farhk e-J^o<juhil/ad\ \__ 
 
 \\ ( ’ frjW/At 
 
 |j m C. NorttriHa , 
 
 l u f V -CPmu m* 
 
 imjECp 
 . 26bi 
 raftienos / 
 
 \Runta cje CachcfSTS 
 IslaCimaCuad r8d^°fA'^ 
 
 A Z 958 / / i u£ 
 
 L^Pujbs't^ 
 
 \\ \ r 
 
 C, de la, Galli 
 
 5340 A ,-' / '^S2| 
 
 / Jfyaur-A^ 
 
 «> / C.Cuer.tectPas / 
 
 1 L*“ (('! 
 
 dAo CrLagunillas-; yj>' 
 t '/ a , G,Mosta§a: y y- 
 
 ri^'WY.'Y 
 
 fdero C. Midai 
 
 • / I / Totc/ral^ 
 
 y' Pun^a To|tora l | ^ 
 
 Y1600 / , . 
 
 i.'del Frait 
 
 C. Plaza 
 
 .Port, & a dirty? 
 , Port.DichqsaJJl 
 
 yV 7 "y 
 
 iZi'&d'A^rsG-rte Laicpt I / 
 
 'Am.nSK- '317/1 
 
 '/«02 
 
 ftjrifl" 
 
 irrizo 
 
 ■;h(JPill(j$- 
 
 ^pUfRUNOp 
 
 1 [f ^rtaec't 
 
 l&ARRQEfo JW 1 
 le' Lomi/a^ BlaOcas 
 
 \ vA-- ;. V 73 
 
 e ArWga v T4r 
 
 CJde Tres.Morros 
 
 ’unta Lobos 
 
 r ° A 2 l 
 
 |/Punta Crucdcita 
 
 Fverde . 
 
 tr(/f7 Saucp f ^ 
 
 a :C -4i 
 
 d^Jnfier-pijlld 
 
 'raw* 
 
 WirrLo del fluag cu /xT^ ifecn- 
 /225 |s| a Batchelor >- r / g ! ^ 2 : giO g ^ 
 
 n ' ; e= f ‘(sftd^ 
 
 ° 0 ' , Mbluascor- if M ^, 
 
 ,x, ^VF^Quijot 
 
 Wv'Juano 
 
 ■^KlBosand- 
 
 Ar.pni'la'i IfftGr a rirf^a'Sj g 
 
 V.; A 1 de^ A7/0 
 
 ^ /7m'? 
 
 ,V : tflmbnVU5ncada.yL fj 
 
 'urerdicesj^. y M 
 
 fsia 
 
 (Alcalde 
 
 M rl CaVu 
 
 3444 
 
 Mfyde pta^uit; 
 ^□ebradti^^ 
 £armenl/x/-}, 
 Bi^ncav^V'^ri 
 
 CaHety/fh Pend Bhinca. 
 
 lAdua.Amarga 1 
 
 ■ C ocroteo 
 
 Barros' 
 
 ■ /Cale/n dt Cnbre 
 
 Btdiui (W Quehr/glq,l/»ailaf_ 
 /Snspdaw MmL /‘S UenoJ /fjf£ 
 Gabo/Bascuiyn ’fc 7 >J A A 
 
 PuntL PaiarosZ Z T\ 
 
 j ^CTtorado Viejo 
 ^ ja ll LtM 9 pado' , ^A> > 
 
 —Trie a 
 'PITAS \ ,1 
 
 : r^‘ 
 
 •ntajo?" 
 
 pi:f >, 
 
 [sau Felix 
 
 mt) 
 
 >s Leones 
 
 / Mina | 
 
 i-u'i ..'■ 
 
 C\de lot 
 
 uljfB’sJ. 
 
 Bihia\de UJrriwL 
 
 638C7, vfy/T 
 
 i-./ /illv. 
 
 Punta Carrizal 
 
 768 \ i ' 
 
 etu. (’£ AprlilldAo 
 
 \ \ \ j, 
 
 Collet a de /A 
 
 j. i__ rkJ- nr 0 
 
 Llanos J 
 
 Carrtz®! 
 
 1 E.I Teroeni 
 
 ft 
 
 los.Chqros 
 
 Isla Gaviota' 
 
 Mar Brdra 
 
 g-Rpcas Toro i 
 -'Isla ChungbngoA 
 Fgnta BarraOcorfes 
 CaleAdB Cnu Grarul 
 Purtfa Mostacill 
 
 Bahia de ^ 
 
 - ,» 
 
 >A 7 1 I Isla 
 
 )6 ' !ls)otes de \y /Q 
 
 658 .' v Pharos \ 
 
 6l j 4 i' j \ Quehraaq Hunrtrn CA, 
 
 S ^.A. ' /.a.V 
 
 \ ' -658 - , ' ' W */' vSl 
 
 * 1 ;»« s7£\ ■' j 
 
 " 7,: X J s ?iGilr/4 .VT.O-CT mwy. fl iy y * 
 
 Santa Qra (: »a - 
 
 -.y - 
 
 ■y a 
 
 x/ ' ^flrl Minillas^iiatpt 
 
 i a PO r Kfo^J-sU^ 
 
 ' ' its!! 
 
 s Wartitos-; 
 
 '•ft A 
 
 de MaKa 
 
 Pbota Pdrdto 
 
 
 Cua.v 
 
 lerto^HertiJ 
 
 xonconta 
 
 ’2900 
 
 '■^x' 
 
 inta Saliente 
 
 tRILLOS* 
 
 '£,1 Pchon 
 
 Punta Lagunilla* 
 
 <le ...\ 47 k^^ 
 
 H | 
 
 £ ay .. mSBAs 
 
 Punta Guanpiquero 
 
 Peninsula 
 /de Tongoi 
 
 Bahia, 
 Ton/joiyt 
 
 iPunta Lengua de Vaca 
 
 il60:M r, CoRr8CQuem30c 
 
 CAndacollo/^% 
 
 d'T) V IcV^. 
 iy / [ < v . 
 
 y t t&CUMBRE '' V 
 
 r r/i xj\ 
 
 (/fAi/i l Cobie 
 
 2 J \t\wA L. a 
 
 j **yifp:}j£REVfSJ \ 
 
 1 \'! h 
 
 itfet/i Totoi 
 
 tajigue\ 
 
 mMm 
 
 l > „ /s ■ ■ 
 
 Pachingt 
 
 \ QULBRADA SECh 
 
 mm 
 
 r*r 7 ) ,di 
 
 i ,'(3; 
 
 77/0 
 
 7 
 
 ^>' N +-**<■ —. Salado ./* 
 
 ^ /^\<L ^; 6 l 9j C.Solo -fe'- 
 ^xr'fo/lVW’- ^ AVtV ? ", br< P' 
 
 luQ- ■ 
 
 C^ 66 ^Z) 
 
 iltororfo 525QL ' 
 
 LO 
 
 / % 
 
 / 633t 
 
 7. N 
 
 ’vr)'. 
 
 Port, de los Sajipji 
 
 \ C.Pab 
 
 roe /' A_C> Piss^T^-^V^ y* ^ 
 
 P “! —", 67^A ' s hndloTy ~ 
 
 C. Violado 67/70 -' 5800 a ''p \ j 
 
 \ C.Punilla ^y* 5 ° 0 J 
 
 ■ w » f6i3o^c.Recius 
 
 isojb/cYT f 6110 l j/r? .pi 
 
 qfe Quebrrdda£ectrNoctz y/ y~\ 
 
 ■**-'**** 7 L~ hf, 
 
 -X 64IQ, , AW//1 
 
 A \~k-7^y/r 
 
 1, . CL. ~AP5t2PzjZ£lbv A „ ?/ - 
 
 ^ JyAW VifY ( 
 
 ^ 1 ((US' 
 
 y H.y rdaM.Rho < 
 
 EXPLANATION 
 
 *§ I Gravel deposits and 
 
 Coquimbo marine sediments 
 Comprises the mantling and fringing 
 gravels in the basins and canyons, but 
 does not shore their widespread occurrences 
 in the high plateau region of the Andes 
 
 Volcanic rocks 
 
 Comprises dioHtes , andesites, trachytes , 
 and liparites , named in the probable 
 sequence of eruption 
 
 Lower Cretaceous (Neocomian) 
 8 7 marine sediments and diabase 
 ■2 j Gray and green shale, thin sandstone, 
 y and limestone , fossiliferous; associated 
 
 ^ with diabase 
 
 Upper Jurassic (Titon) 
 marine sediments 
 
 Limestones and shales, generally dark- 
 colored, fossiliferous 
 
 Middle Jurassic (Dogger) 
 marine sediments 
 
 Undifferentiated 
 Mesozoic, probably 
 
 Limestones and shales , commonly including areas of 
 
 reddish and greenish, fossiliferous; asso¬ 
 ciated with very voluminous flows of 
 labradorite porphyry 
 
 Paleozoic rocks and 
 also of Tertiary 
 volcanics 
 
 Lower Jurassic (Lias) 
 marine sediments 
 
 Calcareous sandstone and limestone, 
 generally gray, fossiliferous 
 
 Upper Triassic (Rhetic) 
 continental deposits 
 
 Very coarse, conglomerates and sand¬ 
 stones with thin irregular coal beds; 
 contains silicifled wood; only locally 
 developed 
 
 All pre-Mesozoic rocks 
 
 Comprises metamorphosed sedimentary 
 rocks , granites, diabase intrusive in 
 granite , and porphyry dikes; the last 
 “ Mesozoit 
 
 named, may be of Mesozoic age 
 
 Faults 
 
 NOTE 
 
 The two broad classifications of rocks. Paleozoic and Mesozoic, are arranged 
 upon the map according to general information beyond the limits of personal 
 observation. The facts of distribution observed along the routes travelled are 
 delineated as they were interpreted at the time so far as the scale of the map 
 permits. The details are beyond the scope of the study, which was neces¬ 
 sarily that of a reconnoissance. 
 
 Base from the Atacama and Coquimbo-San Juan 
 Sheets of the Millionth Map of Hispanic America 
 published by the American Geographical Society 
 of New York 
 
 GEOLOGIC SKETCH MAP OF ATACAMA, CHILE 
 
 Based upon field notes of Bailey Willis and Johannes Feisch, 1923 
 
 A. Hoen &. Co. Lith. 
 
 Scale :u)oo,ooo' 
 
 so Englislx Miles 
 
 KUometevs 
 
LIBRARY 
 OF THE 
 
 UNIVERSITY OF ILLINOIS 
 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXIX 
 
 A. Vallenar. View of valley looking up Huasco river toward the foothills of the Andes; showing high terrace south of river. 
 
 B. Vallenar. Looking north ; view of Huasco valley and broad plain which lies between Coast Range on left and foothills of Andes on right; showing successive terrace levels by which the slope rises in three steps to height of 660 feet (200 meters) above river. 
 
siohW" 
 
 jo u\s»3N' wn 
 3Hi 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXX 
 
 A. Upper Copiapo valley. View from southeast to south and west. On left is Cerro Ladrillos, composed of Jurassic lavas and forming western foothills of Andes. Upper Copiapo valley extends into distance southward. High hills behind trees consist chiefly of Paleozoic granite and diabase. On right is upper portion of basin of Copiapo and locality called Paipote. 
 
 Panoramic view of Rio Elgin, comprising heights of Andes on left and city of Vicuna on right. At this point the Jurassic lavas form an anticline; there are no faults, and the city, although built in the river plain, suffered but little damage. 
 
F 
 
Carnegie Inst. Wash. Pub. 382 (Willis) 
 
 Plate LXXV 
 
 
 Cateclral de Peterborough, vista desde el desembarcndero 
 
 Catedrol de Peterborou 
 
 (S 2 rrmtro# Ofir.) 
 
 D E LA IS LA SAN FELIX, 
 
 Levantado por la Oficialidad de la Goleta “Covadonga 
 al man do del Cap n RAMON VIDAL GORMAZ , 
 
 en 1874. 
 
 LaUhid Su r 
 Lonj. 0. dr Greenwich 
 Ealnblta mien lo. a fir axis 
 Elevation dc las aquas 
 Variation magnelica 
 
 SONDA EN METROS 
 
 ac, arena i conchnela, 
 
 a, a I'm a 
 
 an. arena 
 
 •^tnarUIo 
 
 ESCALA DE 
 
 KiLoindros 
 
 1 nulla 
 
 Eseala de 
 
 Santiago de Chile. Publuado de orden del Serior Mxnistro de 
 
 } yo la. direcdon de la, Ofu 
 
 ^ - Sana- hidrog rdfiea, , enEnero de 1875 
 
 duyusto JUKI. CaHe de. Cochrane, A ? 91 
 
 naraiso 
 
 ( HART OF THE ISLAND OF SAN FELIX PREPARED BY THE COVADONGA EXPEDITION, CAPTAIN RAMON VIDAL GORMAZ, IN CHARGE, 1874 
 
 Facsimile of the official publication by the Minister of the Marine, 1875 
 
 ' • 1 \ 
 
 (B.) Vista entrando al Puerto ,distancia Smillas. (C.) Vista desde el fondeadei