Yosemite in Depth: Geology

Yosemite National Park is well known for its sheer cliffs, beautiful waterfalls, and spectacular landforms. Plate tectonics, subduction, and uplift created and continue to form Yosemite. As they have for millions of years, moving water, wind, and ice will continue to change the face of Yosemite. Nothing is constant but change!

Overview

The story begins some 200 million years ago with the subduction of the oceanic plate and the continental plate off the coast of what is now California. An ancient volcanic Sierra Nevada range was forming.

This was followed 5 million years later by formation of a large granite rock mass or batholith. This granite batholith was exposed 65 million years ago after erosion of the overlying volcanic Sierra Nevada range.

About 60 million years ago, movement at the plate boundaries off California changed from subduction to a strike-slip movement. This led to changes that would cause uplift and tilting of the Sierra Nevada range 25 million years ago. This in turn caused rivers and streams to flow faster, cutting V-shaped river canyons.

About 2.5 million years ago, the world’s climate cooled, and 1.2 million years ago glaciers formed throughout the Sierra Nevada range. These glaciers carved U-shaped valleys. Erosion and weathering continue to change the face of Yosemite today.

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