SIERRA NEVADA

Physical features of western North America. also called Sierra Nevadas, major mountain range of western North America, running along the eastern edge of the U.S. state of California. Its great mass lies between the large Central Valley depression to the west and the Basin and Range Province to the east. Extending more than 250 miles (400 kilometres) northward from the Mohave Desert to the Cascade Range of northern California and Oregon, the Sierra Nevada varies from about 80 miles wide at Lake Tahoe to about 50 miles wide in the south. Its magnificent skyline and spectacular landscapes make it one of the most beautiful physical features of the United States. As a recreation centre, its year-round facilities prove a magnet to the inhabitants of the huge urban areas of California, and it has considerable importance as a source of power and water. It was the focus of the celebrated California gold rush. The Sierra Nevada range is an excellent example of how the human occupation and use of an area can modify its landscape. First mining and later logging and tourism have done more in 150 years to alter the flavour of the mountain scenery in many areas than the actions of ice and water over millennia. also called Sierra Nevadas, major mountain range of western North America, extending for more than 250 miles (400 km) along the eastern edge of the state of California from the Mojave Desert in the south to the Cascade Range in the north. The range is bounded by the plateaus and mountains of the Basin and Range province on the east and by the large Central Valley depression of California on the west. Averaging about 50 miles (80 km) across, the Sierra Nevada's magnificent skyline and spectacular landscapes make it one of the most beautiful physical features of the United States. Its peaks range from 11,000 to 14,000 feet (3,350 to 4,270 m) above sea level; Mount Whitney, the highest peak of the coterminous United States, rises to 14,494 feet (4,418 m). Glaciers formed in the Sierra Nevadas at least five times during the Pleistocene Epoch (about 1,600,000 to 10,000 years ago), leaving behind ice-carved, U-shaped valleys and other glacial features responsible for much of the scenic beauty of the Yosemite, Kings Canyon, and Sequoia national parks. The range's gentle west-facing slope has been dissected by a series of streams that drain into the Central Valley of California by way of the southward-flowing Sacramento River in the north and the northward-flowing San Joaquin River in the south. These two systems ultimately drain the mountains westward to the Pacific Ocean. Moist Pacific winds drop many feet of snow on them annually, making the Sierras the life-sustaining watershed for California's ever growing population and providing water not only for the state's massive irrigation systems and most of its drinking water but also for the many hydroelectric plants constructed in its higher reaches. The site of Sutter's Mill on the American River was the focus of the California gold rush in 184849; the 150-mile (240-kilometre) Mother Lode vein system along the western reaches of the Sierra Nevadas is still being mined. mountain range in southeastern Spain, near the Mediterranean coast, the highest division of the Baetic Cordillera (Sistema Penibtico). The range itself is a domed mountain elongated for about 26 miles (41 km) from east to west. It is clearly defined by the faulted troughs of the vega (plain) of Granada to the northwest, the Guadix tableland to the northeast, and the Alpujarras depression to the south. The highest peak of the range is Mulhacn Peak (11,421 feet ), which is also the highest point of the Iberian Peninsula. Several other summits rise above the snow line of 10,000 feet and have given significance to the name, which means Snowy Range. The range of elevations is reflected in a sequence of flora from subtropical to alpine species. Additional reading On the natural history of the Sierra Nevada, classic accounts of explorations are found in Roderick Peattie (ed.), The Sierra Nevada (1947); John Muir, My First Summer in the Sierra (1911, reissued 1990), a classic of geographic writing, and The Wilderness World of John Muir, compiled by Edwin Way Teale (1954, reissued 1982); and Tracy I. Storer and Robert L. Usinger, Sierra Nevada Natural History: An Illustrated Handbook (1963). Analyses of the geology of the mountains are found in John L. Burnett, Geology of the Lake Tahoe Basin, California Geology, 24(7):119127 (1971); Edward B. Scott, The Saga of Lake Tahoe: A Complete Documentation of Lake Tahoe's Development over the Last One Hundred Years (1957); and Mary Hill, Geology of the Sierra Nevada (1975). The climate is detailed in John W. James, A Record-Breaking Sierra Nevada Snowfall: Its Meteorologic and Topographic Causes, in American Meteorological Society, Third Conference on Mountain Meteorology (1984), pp. 144146; and David H. Miller, Snow Cover and Climate in the Sierra Nevada (1955). John W. James