Geographic Features

Geography of Yosemite

Yosemite National Park is located in the central Sierra Nevada. Three wilderness areas are adjacent to Yosemite: the Ansel Adams Wilderness to the southeast, the Hoover Wilderness to the northeast, and the Emigrant Wilderness to the north.

The 1,189 sq mi (3,080 km2) park contains thousands of lakes and ponds, 1,600 miles (2,600 km) of streams, 800 miles (1,300 km) of hiking trails, and 350 miles (560 km) of roads.[79] Two federally designated Wild and Scenic Rivers, the Merced and the Tuolumne, begin within Yosemite's borders and flow westward through the Sierra foothills into the Central Valley of California.

Rocks and Erosion

Almost all of the landforms are cut from the granitic rock of the Sierra Nevada Batholith (a batholith is a large mass of intrusive igneous rock that formed deep below the surface). About five percent of the park's landforms (mostly in its eastern margin near Mount Dana) are metamorphosed volcanic and sedimentary rocks. These roof pendants once formed the roof over the underlying granitic magma.

Erosion acting upon different types of uplift-generated joint and fracture systems is responsible for producing the valleys, canyons, domes, and other features. These joints and fracture systems do not move, and are therefore not faults. Spacing between joints is controlled by the amount of silica in the granite and granodiorite rocks; more silica tends to form a more resistant rock, resulting in larger spaces between joints and fractures.

Water and Ice

The Tuolumne and Merced River systems originate along the crest of the Sierra in the park and have carved river canyons 3,000 to 4,000 feet deep. The Tuolumne River drains the entire northern portion of the park, an area of approximately 680 square miles. The Merced River begins in the park's southern peaks, primarily the Cathedral and Clark Ranges, and drains an area of approximately 511 square miles.

Hydrologic processes, including glaciation, flooding, and fluvial geomorphic response, have been fundamental in creating park landforms. The park contains approximately 3,200 lakes, two reservoirs, and 1,700 miles of streams. Wetlands flourish in valley bottoms throughout the park, and are often hydrologically linked to nearby lakes and rivers through seasonal flooding and groundwater. Meadow habitats, distributed at elevations from 3,000 to 11,000 feet in the park, are generally wetlands, as are the riparian habitats found on the banks of Yosemite's watercourses.

Climate

Yosemite has a Mediterranean climate (Köppen climate classification Csa), meaning most precipitation falls during the mild winter, and the other seasons are nearly dry (less than three percent of precipitation falls during the long, hot summers). Because of orographic lift, precipitation increases with elevation up to 8,000 feet (2,400 m) where it slowly decreases to the crest. Precipitation amounts vary from 36 inches (910 mm) at 4,000 feet (1,200 m) elevation to 50 inches (1,300 mm) at 8,600 feet (2,600 m). Snow does not typically accumulate until November in the high country. It deepens into March or early April.

Hydrologic processes, including glaciation, flooding, and fluvial geomorphic response, have been fundamental in creating park landforms. The park contains approximately 3,200 lakes, two reservoirs, and 1,700 miles of streams. Wetlands flourish in valley bottoms throughout the park, and are often hydrologically linked to nearby lakes and rivers through seasonal flooding and groundwater. Meadow habitats, distributed at elevations from 3,000 to 11,000 feet in the park, are generally wetlands, as are the riparian habitats found on the banks of Yosemite's watercourses.

Sources