Yosemite National Park

:Yosemite redirects here. For the Looney Tunes/Merrie Melodies character, see Yosemite Sam.

Geography

Yosemite National Park is located in the central Sierra Nevada of California. It takes 3.5 hours to drive to the park from San Francisco and about six hours from Los Angeles. Yosemite is surrounded by wilderness areas: the Ansel Adams Wilderness to the southeast, the Hoover Wilderness to the northeast, and the Emigrant Wilderness to the north.

Related Topics:
San Francisco - Los Angeles - Ansel Adams Wilderness - Hoover Wilderness - Emigrant Wilderness

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The 1,200-square-mile (3,100 km²) park contains thousands of lakes and ponds, 1,600 miles (2,600 km) of streams, 800 miles (1300 km) of hiking trails, and 350 miles (560 km) of roads. Two federally designated wild and scenic rivers, the Merced and Tuolumne, begin within Yosemite's borders and flow west into the Central Valley of California. Annual park visitation exceeds 3.5 million, with most visitor use concentrated in the seven square mile (18 km²) area of Yosemite Valley.

Related Topics:
Lake - Pond - Stream - Hiking - Merced - Tuolumne - Central Valley of California - Yosemite Valley

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Rocks and erosion

Almost all of the landforms in the Yosemite area 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 5% of the park (mostly in its eastern margin near Mount Dana) are from metamorphosed volcanic and sedimentary rocks. These rocks are called "roof pendants" because they were once the roof of the underlying granitic rock.

Related Topics:
Granitic - Sierra Nevada Batholith - Batholith - Igneous rock - Mount Dana - Metamorphosed

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Erosion acting upon different types of uplift-created joint and fracture systems is responsible for creating the valleys, canyons, domes, and other features we see today (these joints and fracture systems do not move, and are therefore not faults). Spacing between joints and fracture systems is largely due to the amount of silica in the granite and granodiorite rocks; more silica tends to create larger spaces between joints and fractures and thus a more resistant rock.

Related Topics:
Erosion - Fault - Silica - Granodiorite

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Pillars and columns, such as Washington Column and Lost Arrow, are created by cross joints. Erosion acting on master joints is responsible for creating valleys and later canyons. The single most erosive force over the last few million years has been from large alpine glaciers, which have turned the previously V-shaped river-cut valleys into U-shaped glacial-cut canyons (such as Yosemite Valley and Hetch Hetchy Valley). Exfoliation (caused by the tendency of crystals in plutonic rocks to expand at the surface) acting on granitic rock with widely spaced joints is responsible for creating domes such as Half Dome and North Dome and inset arches like Royal Arches.

Related Topics:
Glacier - Yosemite Valley - Hetch Hetchy Valley - Exfoliation - Crystal - Half Dome - North Dome

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Popular features

Yosemite Valley represents only one percent of the park area, but this is where most visitors arrive and stay. El Capitan, a prominent granite cliff that looms over the valley, is one of the most popular world destinations for rock climbers because of its diverse range of difficulties and numerous established climbing routes in addition to its year-round accessibility. Impressive granite domes such as Sentinel Dome and Half Dome rise 3,000 feet and 4,800 feet (900 and 1450 m), respectively, above the valley floor.

Related Topics:
El Capitan - Rock climbers - Sentinel Dome - Half Dome

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The high country of Yosemite contains beautiful areas, such as Tuolumne Meadows, Dana Meadows, the Clark Range, the Cathedral Range, and the Kuna Crest. The Sierra crest and the Pacific Crest Trail run through Yosemite, with peaks of red metamorphic rock, such as Mount Dana and Mount Gibbs, and granite peaks, such as Mount Conness. Mount Lyell is the highest point in the park.

Related Topics:
Tuolumne Meadows - Dana Meadows - Clark Range - Cathedral Range - Kuna Crest - Pacific Crest Trail - Metamorphic rock - Mount Dana - Mount Gibbs - Granite - Mount Conness - Mount Lyell

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The park has three groves of ancient Giant Sequoia (Sequoiadendron giganteum) trees; the Mariposa Grove (200 trees), Tuolumne Grove (25 trees), and the Merced Grove (20 trees). Giant Sequoia are the most massive trees in the world and are one of the tallest and longest-lived (Coast Redwoods that live along the Northern Californian coast are the tallest and the Great Basin Bristlecone Pine of Eastern California are the oldest). These trees were once much more widespread before the last Ice Age began (Geology of U.S. Parklands, page 227).

Related Topics:
Giant Sequoia - Mariposa Grove - Tuolumne Grove - Merced Grove - Tree - Coast Redwood - Northern California - Great Basin Bristlecone Pine - Eastern California

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Water and ice

Tuolumne and Merced River systems originate along the crest of the Sierra Nevada in the park and have carved river canyons 3,000 to 4,000 feet (900 to 1200 m) deep. The Tuolumne River drains the entire northern portion of the park, an area of approximately 680 square miles (1760 km²). 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 (1320 km²).

Related Topics:
Tuolumne - Merced River - Cathedral - Clark Ranges

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Hydrologic processes, including glaciation, flooding, and fluvial geomorphic response, have been fundamental in creating landforms in the park. The park also contains approximately 3,200 lakes (greater than 100 square meters), two reservoirs, and 1,700 miles (2700 km) of streams, all of which help form these two large watersheds. Wetlands in Yosemite occur in valley bottoms throughout the park, and are often hydrologically linked to nearby lakes and rivers through seasonal flooding and groundwater movement. Meadow habitats, distributed at elevations from 3,000 to 11,000 feet (900 to 3500 m) in the park, are generally wetlands, as are the riparian habitats found on the banks of Yosemite's numerous streams and rivers.

Related Topics:
Glaciation - Flooding - Lake - Reservoir - Wetland - Meadow - Riparian

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Numerous sheer drops, glacial steps and hanging valleys in the park provide many places for waterfalls to exist, especially during April, May, and June (the snowmelt season). Located in Yosemite Valley, the 2425-foot-high (782 m) Yosemite Falls is the highest in North America and the third highest in the world. Also in the valley is the much lower volume Ribbon Falls, which has the highest single vertical drop, 1612 feet (492 m) (Geology of U.S. Parklands, page 227). Perhaps the most prominent of the Yosemite waterfalls is Bridalveil Fall, which is the waterfall seen from the Tunnel View viewpoint at the east end of the Wawona Tunnel. Wapama Falls in Hetch Hetchy Valley is another notable waterfall.

Related Topics:
Hanging valley - Waterfall - Yosemite Falls - North America - Bridalveil Fall - Wawona Tunnel - Hetch Hetchy Valley

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

All glaciers in the park are relatively small glaciers that occupy areas that are in almost permanent shade, such as north- and northeast-facing cirques. Lyell Glacier is the largest glacier in the Sierra Nevada (and therefore the park) and covers 160 acres (65 ha). None of the Yosemite glaciers are the remnants of the much, much larger Ice Age alpine glaciers responsible for sculpting the Yosemite landscape. Instead, they were formed during one of the neoglacial episodes that have occurred since the thawing of the Ice Age (such as the Little Ice Age). Global warming has reduced the number and size of glaciers around the world. Many Yosemite glaciers, including Merced Glacier, which was discovered by John Muir in 1871 and bolstered his glacial origins theory of the Yosemite area, have disappeared and most of the others have lost up to 75% of their surface area (Geology of U.S. Parklands, page 228).

Related Topics:
Glacier - Cirque - Lyell Glacier - Ice Age - Neoglacial - Little Ice Age - Global warming - John Muir - 1871

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Climate

The area of the park has a Mediterranean climate, meaning almost all yearly precipitation normally falls during mild winter and the other seasons are nearly dry (less than 3% of precipitation falls in the typically long, hot summers). Due to orographic lift precipitation increases with elevation until around 8000 feet (2400 m) when it slowly decreases to the crest. Precipitation amounts vary from 36 inches (915 mm) at 4,000 feet (1200 m) elevation to 50 inches (1200 mm) at 8,600 feet (2600 m). Snow does not typically persist on the ground until November in the high country. It accumulates all winter and into March or early April.

Related Topics:
Mediterranean climate - Orographic lift

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Temperature decreases with increasing elevation. Temperature extremes are moderated by the fact that Yosemite is only about 100 miles (160 km) from the Pacific Ocean. An anticyclone sits off the coast of California in the summer, sending cool air masses toward the Sierra Nevada that result in clean dry air in the Yosemite area.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Mean daily temperatures range from 25 to 53 °F (-3.9 to 11.5 °C) at Tuolumne Meadows at 8,600 feet (2,600 m). At South Entrance near Wawona (elevation 6192 feet; 1887 m), mean daily temperature ranges from 36 to 67 °F (2.2 to 19.4 °C). At the lower elevations below 5,000 feet (1525 m), temperatures are hotter; the mean daily high temperature at Yosemite Valley (elevation 3,966 feet; 1209 m) varies from 46 to 90 °F (7.8 to 32.2 °C). At elevations above 8,000 feet (2440 m), the hot, dry summer temperatures are moderated by frequent summer thunderstorms, along with snow that can persist into July. The combination of dry vegetation, low relative humidity, and thunderstorms results in frequent lightning-caused fires as well.

Related Topics:
Thunderstorm - Vegetation - Humidity - Lightning - Fire

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~