Yosemite National Park
Yosemite National Park is a national park spanning portions of Tuolumne, Mariposa and Madera counties in Northern California. Designated a World Heritage Site in 1984, Yosemite is internationally recognised for its granite cliffs, waterfalls, clear streams, giant sequoia groves, lakes, mountains, glaciers, and biological diversity. Almost 95% of the park is designated wilderness. The geology of the Yosemite area is characterized by granitic rocks and remnants of older rock. About 10 million years ago, the Sierra Nevada was uplifted and then tilted to form its relatively gentle western slopes and the more dramatic eastern slopes. The uplift increased the steepness of stream and river beds, resulting in formation of deep, narrow canyons. About one million years ago, snow and ice accumulated, forming glaciers at the higher alpine meadows that moved down the river valleys. Ice thickness in Yosemite Valley may have reached 1,200 m during the early glacial episode. The downslope movement of the ice masses cut and sculpted the U-shaped valley that attracts so many visitors to its scenic vistas today.