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Yosemite Valley

Geological Places

Yosemite Valley is located in Yosemite National Park in California. It is renowned for its breathtaking granite cliffs, waterfalls, and diverse landscapes.

Formation

Yosemite Valley itself is a result of the carving and shaping of the landscape by powerful glacial forces during multiple ice ages.

Almost all the rock you see in this photo, and the underlying rock of Yosemite National Park is part of the granite batholith underlying most of the Sierra Nevada.
Almost all the rock you see in this photo, and the underlying rock of Yosemite Valley is part of the granite batholith underlying most of the Sierra Nevada. Al Copley photo.

Granite Formation

The predominant rock in Yosemite Valley is granite, particularly a type called granodiorite. This type of rock forms deep beneath the Earth’s surface through the slow cooling and solidification of magma. Over time, the overlying rock layers eroded away, exposing the granitic rock beneath.

Glacial Erosion

During periods of glaciation, massive glaciers formed, advanced, and retreated in the Sierra Nevada Mountains. The glaciers eroded the landscape, shaping the valley. The glaciers acted like giant bulldozers, carrying and grinding rock debris as they moved. The glaciers deepened and widened the valley, leaving behind the distinctive U-shaped profile.

Yosemite’s Cliffs and Waterfalls

The iconic granite cliffs of Yosemite Valley, such as El Capitan and Half Dome, are the result of differential erosion. These cliffs are made up of more resistant granite that has withstood erosion compared to the surrounding rock. Waterfalls, including Yosemite Falls, Bridal-veil Fall, and others, owe their existence to the erosional features created by glaciers and watercourses over time.

Many of these are the result of hanging valleys, which were valleys present before glaciation, but were crossed and cut off by the glacier’s carving of the larger valley.

Glacial Features

The falls in Yosemite National Park are cut into granite sides of the glacial valley.
The falls in Yosemite Valley are cut into granite sides of the glacial valley. Al Copley photo.

Evidence of glaciation is visible in Yosemite Valley through the presence of glacial polish, striations (grooves) on rock surfaces, and glacially-carved features like the hanging valleys and the larger U-shaped valleys.

Erosional Processes

Even after the retreat of glaciers, erosion continues to shape Yosemite Valley. The Merced River in the valley continues to carve its course, contributing to the valley’s dynamic landscape.

Granite Monoliths

Half Dome and El Capitan are just two of the prominent granite monoliths that draw attention due to their sheer size and vertical faces. These monoliths are composed of resilient granite that resisted erosion while the surrounding rock eroded away. Yosemite National Park is easily visited, just a few hours east of San Francisco. Because weather can close the valley at any time of year, and visitation is extremely heavy during good weather, it is really recommended to check the park’s website for current visiting information.

Half Dome in Yosemite National Park, California, is primarily composed of granite.
Half Dome in Yosemite Valley, California, is primarily composed of granite. Al Copley photo.