WMOD00304

• Project Name: Sierra Ecology Project
• Title: The Sierra Ecology Project - Volume I - Workshops I, II and III
• Date: 5/11/1978
• Weather Modification - Doc Type: Report

GEOLOGY

Much of the geologic history of the Siera Nevada is reflected in the
landforms and rock types of the American River Basin. The Sierra
Nevada is a large tilted block nearly 640 km (400 mi) long and 95 to
130 km (60 to 80 mi) wide. It has a long, gentle western slope and
a short, very steep, spectacular eastern slope that marks a fault
scarp which becomes an echelon in its northern part.

The range has undergone several important orogenic episodes reflect-

ing tectonic forces arising from the Pacific plate contacting and

sliding beneath the North American plate. In the area between the

western part of the present Great Valley of California and well east

of the present Sierra Nevada, Paleozoic and Mesozoic marine sedimen-

tary and volcanic rocks were complexly deformed by repeated episodes

of folding and faulting. Jurassic-Cretaceous intrusions of granitic

magma formed the Sierran batholith and caused regional metamorphism

of the oyer lying rocks.

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