27. Atacama Fault, Chile Coast, South of Antofagasta
The Pacific oceanic plate is being subducted at about nine centimeters (3.5 inches) per year beneath the South American continent along much of the west coast of South America. Oceanic/continental convergence of this sort characteristically produces elevation and shortening by folding and thrusting. These structures are well developed in the eastern foothills of the Andes. The western parts of the Andes are characterized by more complex structures, and both normal faults (usually suggestive of extension) and strike-slip faults are present. Illustrated in the picture is the trace of the important Atacama fault, which runs for several hundred kilometers parallel to the coast of Chile and the deep ocean trench. The fault cuts Paleozoic and Mesozoic metamorphic rocks of the Chilean coastal cordillera.
The tectonic details of the fault are poorly known at present. The fault is thought to have been active over a long period, and both normal and strike-slip movements have been postulated.
STS-41B, February 1984. Picture #11-41-2361.