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Geology of Mount Shasta

Figure 16

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Regional Geologic Map Legend

Age Symbol Map unit description
Surficial deposits of glacial and stream sediments.
Volcanic and glacial deposits of modern and ancestral Mount Shasta.
Volcanic debris avalanche deposit from the collapse of ancestral Mount Shasta.
High Cascade volcanic rocks younger than 1.8 million years (excluding Mount Shasta).
High Cascade volcanic rocks older than 1.8 million years.
Western Cascade volcanic rocks.
Pre-Cascade bedrock including the Trinity ultramafic complex, Paleozoic metamorphic rocks, and the Cretaceous Hornbrook Formation.
Figure 16: Generalized geologic map of the Mount Shasta region compiled from maps by Wagner and Saucedo (1987) and Christiansen (Christiansen and Ernst, 2001). The towns shown on the mountain's western and southern flanks are: W = Weed; MS = Mount Shasta City; and MC = McCloud.

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