|
Geography The Sierra Nevada stretches 400 miles (650 km), from Fredonyer Pass in the north to Tehachapi Pass in the south. It is bounded on the west by California's Central Valley, and on the east by the Great Basin. In west-east cross section, the Sierra is shaped like a non-equilateral triangle: the altitude gradually increases as you travel east, until you reach the crest, whereupon the altitude rapidly decreases, forming a steep escarpment. Thus, the crest runs principally along the eastern edge of the Sierra Nevada range. Rivers flowing west from the Sierra crest eventually drain into the Pacific Ocean, while rivers draining east flow into the Great Basin and do not reach any ocean. However, water from several streams and the Owens River is redirected to the city of Los Angeles (see Los Angeles Aqueduct). Thus, some east-flowing river water does make it to the Pacific Ocean. There are several notable geographical features in the Sierra Nevada: The height of the mountains in the Sierra Nevada gradually increases from north to south. Between Fredonyer Pass and Lake Tahoe, the peaks range from 5,000 ft. (1,524 m) to 8,000 ft. (2,438 m).The crest near Lake Tahoe is roughly 9,000 ft (2,700 m) high, with several peaks as high as Mount Rose (10,778 ft. or 3,285 m), the crest near Yosemite National Park is roughly 13,000 ft (4,000 m) high at Mount Dana and Mount Lyell, and the entire range attains its peak at Mount Whitney. South of Mount Whitney, the range diminishes in elevation, but there are still several highpoints like Florence Peak (12,405 ft. or 3,781 m) and Olancha Peak (12,123 ft. or 3,695 m). The range still climbs almost to 10,000 ft. (3,048 m) near Isabella Lake, but south of the lake, the peaks reach only to a modest 8,000 ft. (2,438 m). Geology See Geology of the Yosemite area for a detailed article about the geology of the central Sierra Nevada. The geological history of the Sierra Nevada begins in the Jurassic period, approximately 150 million years ago. At that time, an island arc collided with the West coast of North America and raised a set of mountains, in an event called the Nevadan orogeny. This event produced metamorphic rock. At roughly the same time, a subduction zone started to form at the edge of the continent. This means that an oceanic plate started to dive beneath the North American plate. Magma from the melting oceanic plate rose and created plutons of solid granite, deep below the surface. These plutons formed at various times, from 115 million to 87 million years ago. By 65 million years ago, the proto-Sierra Nevada was worn down to a range of rolling low mountains, a few thousand feet high. About 25 million years ago, the Sierra Nevada started to rise and tilt to the west. Rivers started cutting deep canyons on both sides of the range. The Earth's climate cooled, and ice ages started about 2.5 million years ago. Glaciers carved out characteristic U-shaped canyons throughout the Sierra. The combination of river and glacier erosion exposed the granitic plutons previously buried, leaving only a remnant of metamorphic rock on top of some Sierra peaks. The rocks of the ancient plutons are known as the Sierra Nevada batholith. Uplift of the Sierra Nevada continues today, especially along its eastern side. This uplift causes large earthquakes, such as the Lone Pine earthquake of 1872. Biology Main article: Biology of the Sierra Nevada The Sierra Nevada are divided into a number of biotic zones• History of Exploration
History of the Name
Trivia A unique peculiarity of the Sierra Nevada is that, under certain wind conditions, a large circular tube of air begins to roll on the southeast side. This is known as the "Sierra Nevada Rotor." This "mountain wave" forms when dry continental winds from the east cause the formation of a stacked set of counter-revolving cylinders of air reaching into the stratosphere. As of 2004, no sailplane has found its top. Similar features occur on many mountain ranges, but it is often observed and utilized in the Sierra. The phenomenon was the subject of an Air Force-funded study in the early 1950s called the Sierra Wave Project. All recent world altitude records set in unpowered aircraft were set in the Sierra Nevada Wave, most flown from Mojave Airport. The Sierra Nevada casts the valleys east of the Sierra in a rain shadow, which makes Death Valley and Owens Valley "the land of little rain". Sierra Nevada has been featured as race track in a Video Game 'Road Rash'. Ref See also | ||||||||||||||
|
| |||||||||||||||
 |
|
| |