Yosemite National Park is a United States National Park spanning eastern portions of Tuolumne, Mariposa and Madera counties in the central eastern portion of California, United States. The park covers an area of 761,268 acres (3,080.74 km2) and reaches across the western slopes of the Sierra Nevada mountain chain. Over 3.7 million people visit Yosemite each year: most spend their time in the seven square miles (18 km2) of Yosemite Valley.
Designated a World Heritage Site in 1984, Yosemite is internationally recognized for its spectacular granite cliffs, waterfalls, clear streams, Giant Sequoia groves, and biological diversity. Almost 95% of the park is designated wilderness. Although not the first designated national park, Yosemite was central to the development of the national park idea, largely owing to the work of people like Galen Clark and John Muir.
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's landforms (mostly in its eastern margin near Mount Dana) are metamorphosed volcanic and sedimentary rocks. These rocks are called roof pendants because they were once the roof of the underlying granitic rock.
Yosemite Valley represents only one percent of the park area, but this is where most visitors arrive and stay. The Tunnel View is the first view of the Valley for many visitors and is extensively photographed. El Capitan, a prominent granite cliff that looms over Yosemite Valley, is one of the most popular rock climbing destinations in the world because of its diverse range of climbing routes in addition to its year-round accessibility.
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 (910 to 1,200 m) deep. The Tuolumne River drains the entire northern portion of the park, an area of approximately 680 square miles (1,800 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 (1,320 km2).
Yosemite has a Mediterranean climate, meaning most precipitation falls during the mild winter, and the other seasons are nearly dry (less than 3% 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).
In 1855, entrepreneur James Mason Hutchings, artist Thomas Ayres and two others were the first to tour the area. Hutchings and Ayers were responsible for much of the earliest publicity about Yosemite, creating articles and entire magazine issues about the Valley. Ayres' highly detailed angularly exaggerated artwork and his written accounts were distributed nationally and an art exhibition of his drawings was held in New York City.
U.S. National Park Service
The National Park Service was formed in 1916, and Yosemite was transferred to that agency's jurisdiction. Tuolumne Meadows Lodge, Tioga Pass Road, and campgrounds at Tenaya and Merced lakes were also completed in 1916. Automobiles started to enter the park in ever-increasing numbers following the construction of all-weather highways to the park. The Yosemite Museum was founded in 1926 through the efforts of Ansel Franklin Hall.
Tectonic And Volcanic Activity
The area of the park was astride a passive continental margin during the Precambrian and early Paleozoic. Sediment was derived from continental sources and was deposited in shallow water. These rocks have since been metamorphosed. Heat generated from the Farallon Plate subducting below the North American Plate led to the creation of an island arc of volcanoes on the west coast of proto-North America between the late Devonian and Permian periods.
Yosemite Valley is open year-round, but much of the remaining park is closed because of snow in late autumn and re-opens in mid to late spring. Open-air tours around Yosemite Valley and the Mariposa Grove of Giant Sequoias are available. Many people enjoy short walks and longer hikes to waterfalls in Yosemite Valley, or walks amongst Giant Sequoias in the Mariposa, Tuolumne, or Merced Groves.
Over 800 miles (1,300 km) of trails are available to hikers —anything from the easy stroll, to the grueling hikes up several park mountains, to multiple-day backpack trips. The park can be divided into 5 sections for the day-user—Yosemite Valley, Wawona/Mariposa Grove/ Glacier Point, Tuolumne Meadows, Hetch Hetchy, and Crane Flat/White Wolf. Numerous books describe park trails, and free information is available from the Park Service in Yosemite.
Rock climbing is an important part of Yosemite. Camp 4, a walk-in campground in Yosemite Valley, was instrumental in the development of rock climbing as a sport, and is listed on the National Register of Historic Places. Climbers can generally be spotted in the snow-free months on anything from ten-foot-high (3 m) boulders to the 3,300-foot (1.0 km) face of El Capitan. Classes are offered by numerous groups on rock climbing.
Many of the roads in the park close because of heavy snow in winter; however, Yosemite Valley is open all year long. Downhill skiing is available at the Badger Pass Ski Area—the oldest downhill skiing area in California, offering downhill skiing from mid-December through early April. Much of the park is open to cross-country skiing and snowshoeing, with several backcountry ski huts open for use. Wilderness permits are required for backcountry overnight ski trips.