Yosemite National Park

Each year, nearly 4 million visitors travel to Yosemite to experience its dramatic landscapes, world-famous rock formations, and remarkable biodiversity. The park's centerpiece, Yosemite Valley, is a glacially carved canyon approximately 7.5 miles (12 km) long, surrounded by towering granite walls rising more than 3,000 feet (914 meters) above the valley floor. Few places on Earth display the immense power of glaciers and geological forces as dramatically as Yosemite.

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Geological History

Yosemite's landscape tells a story spanning more than 100 million years, making it one of the finest examples of glacial geology in North America. Most of the park is underlain by the Sierra Nevada Batholith, a vast body of granite that formed deep beneath the Earth's surface during the Late Jurassic and Cretaceous periods, approximately 105 to 85 million years ago.

At that time, the western edge of North America was an active tectonic boundary where the ancient Farallon Plate was subducting beneath the continent. This process generated enormous quantities of molten magma that slowly cooled underground to form coarse-grained granite. Over millions of years, erosion stripped away the overlying rock, gradually exposing the granite landscape visitors see today.

The Sierra Nevada mountain range itself was uplifted beginning about 10 million years ago, increasing river gradients and accelerating erosion. However, the defining features of Yosemite were sculpted much later during the Ice Ages (Pleistocene Epoch), when massive glaciers repeatedly advanced and retreated through the region over the past 2.6 million years.

These glaciers carved Yosemite Valley into its distinctive U-shaped profile, polishing granite walls, deepening river channels, and creating hanging valleys that now produce many of Yosemite's spectacular waterfalls. The glaciers also left behind domes, moraines, polished rock surfaces, and countless alpine lakes that define the park's scenery today.

Unlike the steep V-shaped valleys created by rivers, Yosemite's broad valley floor and nearly vertical granite cliffs are unmistakable signatures of glacial erosion.