354 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



At about latitude 41° S. the coast range again consists of a series 

 of low hills of metamorphic rocks. The central valley is broad ; and 

 the Andes Mountains are more clearly defined. Farther south the 

 coastal range becomes the Isla Chiloe and the Archipelago de Los 

 Chonos. The lake basins join with the central valley to form the in- 

 land waterway of the archipelago. At about the Peninsula de Taitao 

 the coastal range merges with the Andes, and the central valley again 

 becomes indistinguishable, except as a troughlike channel marking 

 the great faults in Estuario de Los Elefantes, in Canal Moraleda, and 

 in Canal Errazuriz. The faults at this point swing seaward and 

 are lost beneath the ocean. 



This region has a topography similar to that of southeastern Alaska, 

 where glaciers have scoured out the ground rock in the fault zones 

 leaving the structure of the region clearly exposed [13]. Long faults 

 abound. The fault of Estuario de Los Elefantes has, near Laguna 

 San Eafael, recent escarpments in the alluvium several tens of meters 

 in height. 



Another important fault begins about Volcan Michinmavida (fig. 

 3), passes through Estuario Reloncavi, Cayutue, and Lago Todos los 

 Santos and continues northward below or near Volcan Puyehue. The 

 fault is marked by a long, trougliiike valley with volcanoes on either 

 side that, occasionally, obstruct the valley. This general zone, with 

 a similar line slightly west along which volcanoes Shoshuence, Villar- 

 rica, Llaima, Lonquimay, Calafquen, and Antuco are found (fig. 2), 

 extends to the region of Lago Laja and possibly farther north. 

 Klohn^ has described this lineament as a volcanic fracture zone. The 

 topography is strongly suggestive of strike-slip faulting in the past, 

 although it may no longer be active as a strike-slip fault. This com- 

 plex of faulting marked the eastern edge of the active zone during 

 this sequence of earthquakes. A similar, possibly related, fault con- 

 necting with this one is clearly indicated by the courses of Rio Frio 

 and Rio Palena. 



The offshore topography is quite interesting. A long, narrow 

 ocean deep parallels the Chilean coast and is bounded on the east by 

 a great scarp running roughly parallel to the coast. For example, 

 along latitude 41° S. the sea deepens gradually, reaching a depth of 

 some 1,000 m. 60 km. from shore; 18 km. farther offshore the depth 

 becomes 3,562 m. 



During the last 2 years a study of faulting in Chile has been under- 

 taken in collaboration with Prof. Clarence R. Allen, of the California 

 Institute of Teclmology, with emphasis upon work in the Atacama 

 Desert of northern Chile. In general, the faulting in the northern 

 and central parts of the country consists of two conjugate systems, one 



' Oral communication from Carlos Klohn to Pierre Saint-Amand, dated 1960. 



