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Tioga Road (Hwy 120 through the park) and Glacier Point Roads are Closed for the Season - The Tioga Road (Highway 120 through the park from Crane Flat to Tioga Pass) and Glacier Point Road are closed due to snow; there is no estimated opening date, although they usually open sometime in May. More


Yosemite Geology

environment at Yosemite
For 500 million years, the geology of Yosemite has been evolving from an ocean floor to gentle, rolling hills to the formation of the steep Sierra Nevada mountain range with deep river canyons.

Three million years ago, the Ice Ages brought glaciers that scraped and carved the valleys and canyons with such force that the remaining granite still shows the direction of glacial movement. When the last glacier finally melted approximately 10,000 years ago, rock debris dammed the valley and created Lake Yosemite. Tributary creeks plummeted off sheer cliffs and gave birth to the Park's famed waterfalls. Sediment continued to fill the lake through natural processes until it eventually formed the Yosemite Valley floor.

Yosemite's geological evolution continues today as Mirror Lake slowly fills with sediment as Lake Yosemite did. In 1996, the Happy Isles rockfall sent 80,000 tons of rock to the valley floor at 160 mph, proof that powerful forces are still at work.

From every vantage point in Yosemite there are breathtaking geological formations, including mountains, waterfalls, meadows and forests. In fact, Galen Clark, known as the "Guardian of Yosemite" for 20 years, proclaimed it the "grandest of all God's temples."