Death Valley

Death Valley
an arid basin in E California and S Nevada: lowest land in North America. ab. 1500 sq. mi. (3900 sq. km); 280 ft. (85 m) below sea level.

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Valley, southeastern California, U.S. The lowest, hottest, driest portion of North America, it is about 140 mi (225 km) long and 5–15 mi (8–24 km) wide.

The Amargosa River flows into it from the south and contains a small pool, Badwater, that at 282 ft (86 m) below sea level is the lowest point in North America. Death Valley was formerly an obstacle to pioneer settlers (hence its name); it later was a centre of borax mining. Declared a national monument in 1933, it was made a national park in 1994; the park covers 5,219 sq mi (13,517 sq km) and extends into Nevada.

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 structural depression primarily in Inyo county, southeastern California, U.S. It is the lowest, hottest, driest portion of the North American continent. Death Valley is about 140 miles (225 km) long, trends roughly north-south, and is from 5 to 15 miles (8 to 24 km) wide. The valley is bounded on the west by the Panamint Range and on the east by the Black, Funeral, and Grapevine mountains of the Amargosa Range. It lies near the undefined border between the Great Basin and the Mojave Desert.

      Geologically, Death Valley forms part of the southwestern portion of the Great Basin. It is similar to other structural basins of the region but is unique in its depth. Portions of the great salt pan that forms part of the floor of the valley are the lowest land areas of the Americas. About 550 square miles (1,425 square km) of the valley's floor lie below sea level. A point in Badwater Basin, lying 282 feet (86 metres) below sea level, is the lowest area in the Western Hemisphere. Less than 20 miles (30 km) west is the 11,049-foot (3,368-metre) Telescope Peak, the area's highest point. Death Valley was an obstacle to movements of pioneer settlers (whence its name was derived) and later was a centre of borax exploitation; its extreme environment now attracts tourists and scientists.

Physical environment
      For a short time after its christening in 1849 by a hapless party of emigrants who endured intense suffering while crossing it, Death Valley was little known except to Native Americans (primarily Shoshone) of the area and to prospectors searching the surrounding mountains. The first scientific notice of the valley seems to have been a brief mention published in 1868 by a California state geologist. The area remained seldom visited until the 1870s, when gold and silver were discovered in the surrounding mountains, and 1880s, when borax deposits were found in the valley. Borax production, notably at the Harmony Borax Works (1883–88), gave rise to the famous 20-mule team wagons, which hauled the product to Mojave, California. Several ghost towns are located around the valley, and some still contain ruined buildings. They sprang up from the late 19th to the early 20th century following gold, copper, and silver strikes in the area. Deserted when the mines were depleted, each existed for only a few years. For example, Rhyolite, founded in 1904, was a gold-mining boomtown of 10,000 people with its own stock exchange, electric plant, and opera; in 1911 the main mine was closed, and the town was deserted by 1916.

      The geologic history of Death Valley is extremely complex and involves different types of fault activity at various periods, in addition to crustal sinking and even some volcanic activity. Essentially, Death Valley is a graben, or rift valley, formed by the sinking of a tremendous expanse of rock lying between parallel uplifted, tilted-block mountain ranges to the east and west. A type of fault activity called block faulting, in which the movement is predominantly vertical, began to form the valley in the middle of the Tertiary Period (about 30 million years ago). As crustal blocks sank, they formed the great trough of the valley, and other blocks were uplifted to gradually form the adjacent mountain ranges. As the valley sank, it was filled by sediments that were eroded from the surrounding hills; in the central part of the valley the bedrock floor is buried beneath as much as 9,000 feet (2,745 metres) of sediment. The valley floor has continued to tilt and sink.

      The floor of Death Valley is noted for its extremes of temperature and aridity. A record North American high shaded air temperature of 134 °F (57 °C) was recorded in 1913, and summer temperatures often exceed 120 °F (49 °C). The hottest summer on record (1996) saw temperatures top 120 °F on 40 days. Ground temperatures as high as 201 °F (94 °C) have been reported. The high temperatures and low humidity contribute to an exceptionally high evaporation rate.

      Winter minimum temperatures rarely fall to the freezing point; the record lowest temperature was 15 °F (−9 °C). Most rainfall is blocked by the mountains to the west, so the valley is extremely arid. In a 50-year period in the 20th century, the average annual rainfall at Furnace Creek was only 1.66 inches (42.2 mm), the maximum annual rainfall was 4.5 inches (114.3 mm), and two years passed with no measurable rainfall.

      Most of the surface water in Death Valley is in the saline ponds and marshes around the salt pan. The Amargosa River brings some water into the southern end of the valley from desert areas to the east, but most of its flow is underground. Salt Creek, draining the northern arm of the valley, also has only short stretches of perennial surface flow.

      At times in the past, much more water reached Death Valley. During the Wisconsin Glacial Stage of the Pleistocene Epoch, perhaps about 50,000 years ago, a body of water (Lake Manly) filled the valley to a depth of as much as 600 feet (180 metres). More recently, some 2,000 to 5,000 years ago, a shallow lake occupied the floor of the valley, its evaporation producing the present salt pan.

Plant and animal life
      Lack of water makes Death Valley a desert, but it is by no means devoid of life. Plant life above the microscopic level is absent from the salt pan, but salt-tolerant pickleweed, salt grass, and rushes grow around the springs and marshes at its edges. Introduced tamarisks provide shade around some of the springs and in the inhabited areas at Furnace Creek, but, because they crowd out native vegetation, eradication efforts are ongoing. Mesquite flourishes where less-saline water is available. Creosote bush dominates the gravel fan surfaces around most of the valley, giving way to desert holly at the lowest elevations. Cactus is rare in the lowest part of the valley but abundant on the fans farther north. Higher elevations support juniper and piñon pine. Spring rains bring out a great variety of desert wildflowers.

      Animal life is varied, although nocturnal habits conceal many of the animals from visitors to the valley. Rabbits and several types of rodents, including antelope ground squirrels, kangaroo rats, and desert wood rats, are present and are the prey of coyotes, kit foxes, and bobcats. The largest native mammal in the area, and perhaps the best-studied member of the fauna, is the desert bighorn (bighorn sheep). Small herds of these sheep are most commonly found in the mountains surrounding Death Valley, but they occasionally visit the valley floor. Wild burros (donkey), descendants of animals lost or abandoned by prospectors and miners, became so numerous as to threaten, through overgrazing, the natural vegetation on which other animals depend. Burro removal began in the 1960s, and live-capture efforts were subsequently attempted in hopes of eliminating the population.

      Though it may seem that the only birds present are the raucous and numerous ravens, the first biological survey of the valley, in the 1890s, reported 78 species of birds. More than three times that number are now known to inhabit or visit the area, the roadrunner being a particularly well-known resident. Lizards, snakes (including rattlesnakes such as sidewinders), and scorpions are common. Even native fish are to be found in Death Valley. Several species of pupfish of the genus Cyprinodon live in Salt Creek and other permanent bodies of water; the highly endangered Devils Hole pupfish (C. diabolis) lives in a single desert pool.

Death Valley National Park
      Death Valley National Park covers some 5,270 square miles (13,650 square km) of the valley, primarily in California. Much of the park's northeastern border is the Nevada state line, but a small portion extends into Nevada's Bullfrog Hills. Inyo National Forest and the Inyo Mountains border it to the west, the Panamint Valley and the Slate Range lie to the southwest, and the U.S. Army's Fort Irwin and the National Training Center adjoin it to the south. The Amargosa River and the Greenwater Range constitute parts of the southeastern border. Death Valley was originally designated a national monument in 1933 and made a national park in 1994. Today's national park covers considerably more area than the original national monument. The national monument was expanded several times, including in 1937 and in 1952, when Devils Hole, located in Nevada's Ash Meadows National Wildlife Refuge, was added. In 1994 the California Desert Protection Act added more than 2,000 square miles (5,100 square km) and redesignated it a national park, the largest in the 48 conterminous U.S. states.

 The park contains a number of unique landforms. The five dune areas include the 680-foot- (205-metre-) high Eureka Sand Dunes, California's tallest. The northern section of the park is dotted with volcanic craters such as Ubehebe Crater, 700 feet (215 metres) deep and 0.5 mile (0.8 km) wide. At Racetrack Playa, rocks as large as 700 pounds (320 kg) leave trails as they mysteriously slide across a flat area; they are probably blown by wind when precipitation creates a moist, slippery clay surface. Other attractions include Scotty's Castle, a mansion built in the 1920s by Chicago businessman Albert Johnson and named for his prospector friend Walter Scott, a spinner of tall tales known as “Death Valley Scotty.” Artist's Drive is an 8-mile (13-km) loop through colourful mountains and canyons. Jagged pinnacles of salt form on the salt pan at Devil's Golf Course. The main visitor centre is at Furnace Creek in the central part of the park and includes exhibits on history, geology, and nature; a second visitor centre is at Beatty, Nevada, outside the park's eastern boundary. Nearby attractions include Kings Canyon (Kings Canyon National Park) and Sequoia (Sequoia National Park) national parks, Manzanar National Historic Site (see Manzanar Relocation Center (Manzanar War Relocation Center)), and Mojave National Preserve.

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Universalium. 2010.

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