Америка Құрама Штаттарының Сьерра-Невада таулары

Mountain range in the United States

The Sierra Nevada (/s//i/,/ɛr//ə// //n//ɪ/'/v//æ//d//ə//, // /'/v//ɑː//d// / seeERRə nivA(H)Də) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily in Nevada. The Sierra Nevada is part of the American Cordillera, an almost continuous chain of mountain ranges that forms the western "backbone" of the Americas. The Sierra runs 400 mile (644 km) north south and its width ranges from 50 mile (80 km) to 80 mile (129 km) across east–west. and erosion by glaciers exposed the granite and formed the light colored mountains and cliffs that make up the range. The uplift caused a wide range of elevations and climates in the Sierra Nevada, which are reflected by the presence of five life zones (areas with similar plant and animal communities). Uplift continues due to faulting caused by tectonic forces, creating spectacular fault block escarpments along the eastern edge of the southern Sierra. The Sierra Nevada has played an important role in the history of California and the United States. The California Gold Rush occurred in the western foothills from 1848 through 1855. Due to its inaccessibility, the range was not fully explored until 1912.]] Used in 1542 by Juan Rodríguez Cabrillo to describe a Pacific Coast Range (Santa Cruz Mountains), the term "Sierra Nevada" was a general identification of less familiar ranges toward the interior. In 1776, Pedro Font's map applied the name to the range currently known as the Sierra Nevada. The literal translation is "snowy mountains", from sierra "a range of mountains", 1610s, from Spanish sierra "jagged mountain range", lit. "saw", from Latin serra "a saw"; and from fem. of Spanish nevado "snowy". While many mountain ranges are unanimously referred to in the plural (Smokies, Rockies, Cascades, etc. ), since Sierra is already pluralized in its native language, some locals who live in "the Sierra" are not hesitant to admonish those who refer to the area as "the Sierras". Ansel Adams, in response to a publication of his photographs under the title Parmelian Prints of the High Sierras, commented, "The name Sierra is already a plural. To add an s is a linguistic, Californian, and mountaineering sin."

The Sierra Nevada lies primarily in central and eastern California, with the Carson Range, a small but historically important spur, extending into Nevada. West to east, the Sierra Nevada's elevation increases gradually from 500 feet (152 m) in the Central Valley and Fredonyer Pass to the North Fork Feather River. It represents where the granitic bedrock of the Sierra Nevada dives below the southern extent of Cenozoic igneous surface rock from the Cascade Range. It is bounded on the west by California's Central Valley, on the east by the Basin and Range Province, and on the southeast by the Mojave Desert. The southern boundary is at Tehachapi Pass.

The range is drained on its western slope by the Central Valley watershed, which discharges into the Pacific Ocean at San Francisco. The northern third of the western Sierra is part of the Sacramento River watershed (including the Feather, Yuba, and American River tributaries), and the middle third is drained by the San Joaquin River (including the Mokelumne, Stanislaus, Tuolumne, and Merced River tributaries). The southern third of the range is drained by the Kings, Kaweah, Tule, and Kern rivers, which flow into the endorheic basin of Tulare Lake, which rarely overflows into the San Joaquin during wet years. The eastern slope watershed of the Sierra is much narrower; its rivers flow out into the endorheic Great Basin of eastern California and western Nevada. From north to south, the Susan River flows into intermittent Honey Lake, the Truckee River flows from Lake Tahoe into Pyramid Lake, the Carson River runs into Carson Sink, the Walker River into Walker Lake; Rush, Lee Vining and Mill Creeks flow into Mono Lake; and the Owens River into dry Owens Lake. Although none of the eastern rivers reach the sea, many of the streams from Mono Lake southwards are diverted into the Los Angeles Aqueduct which provides water to Southern California.

The height of the mountains in the Sierra Nevada increases gradually from north to south. Between Fredonyer Pass and Lake Tahoe, the peaks range from 5000 feet (1524 m) to more than 9000 feet (2743 m). The crest near Lake Tahoe is roughly 9000 feet (2743 m) high, with several peaks approaching the height of Freel Peak (3316.53 m). Farther south, the highest peak in Yosemite National Park is Mount Lyell (3998.98 m). The Sierra rises to almost 14000 feet (4267 m) with Mount Humphreys near Bishop, California. Finally, near Lone Pine, Mount Whitney is at 14505 feet (4421 m), the highest point in the contiguous United States. South of Mount Whitney, the elevation of the range quickly dwindles. The crest elevation is almost 10000 feet (3048 m) near Lake Isabella, but south of the lake, the peaks reach only a modest 8000 feet (2438 m).

Communities in the Sierra Nevada include Paradise, South Lake Tahoe, Truckee, Grass Valley, Lee Vining, Mammoth Lakes, Sonora, Nevada City, Placerville, Pollock Pines, Portola, Auburn, Colfax and Kennedy Meadows.

Much of the Sierra Nevada consists of federal lands and is either protected from development or strictly managed. The mountain range is home to three National ParksYosemite, Kings Canyon, and Sequoiaand two national monumentsDevils Postpile and Giant Sequoia. Ten national forests span much of the mountain range's remaining area. Within these national parks, monuments, and forests lie 26 wilderness areas, which together protect 15.4% of the Sierra's from logging and grazing. The United States Forest Service and the Bureau of Land Management currently control 52% of the land in the Sierra Nevada.

[[File:Sevehah Cliff. jpg|thumb|right|Sevehah Cliff, near Convict Lake, shows severely deformed Devonian rock These dark colored hornfels, slates, marbles, and schists are found in the western foothills (notably around Coarsegold, west of the Tehachapi Pass) and east of the Sierra Crest. The earliest granite of the Sierra started to form in the Triassic period. This granite is mostly found east of the crest and north of 37.2°N. In the Triassic and into the Jurassic, an island arc collided with the west coast of North America and raised a chain of volcanoes, in an event called the Nevadan orogeny. Nearly all subaerial Sierran Arc volcanoes have since disappeared; their remains were redeposited during the Great Valley Sequence and the subsequent Cenozoic filling of the Great Valley, which is the source of much of the sedimentary rock in California. In the Cretaceous, a subduction zone formed at the edge of the continent. This means that an oceanic plate started to dive beneath the North American plate. Magma, formed through the subduction of the ancient Farallon Plate, rose in plumes (plutons) deep underground, their combined mass forming what is called the Sierra Nevada batholith. These plutons formed at various times, from 115 Ma to 87 Ma. Twenty million years ago, crustal extension associated with the Basin and Range Province caused extensive volcanism in the Sierra. About 10 Ma, the Sierra Nevada started to form when a block of crust between the Coast Range and the Basin and Range Province started to tilt to the west as heat from the Basin and Range extension thinned the eastern part of the block, making it more buoyant than the western portion of the block. Rivers started cutting deep canyons on both sides of the range. Lava filled some of these canyons, which have subsequently eroded leaving table mountains that follow the old river channels. About 2.5 Ma, the Earth's climate cooled, and ice ages started. Glaciers carved out characteristic U shaped canyons throughout the Sierra. The combination of river and glacier erosion exposed the uppermost portions of the plutons emplaced millions of years before, leaving only a remnant of metamorphic rock on top of some Sierra peaks. 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.

thumb|Red Slate Mountain (elevation 4009.95 m) is still covered with snow in June

The climate of the Sierra Nevada is influenced by the Mediterranean climate of California. During the fall, winter and spring, precipitation in the Sierra ranges from where it occurs mostly as snow above 1828.80 m. Precipitation is highest on the central and northern portions of the western slope between elevation, due to orographic lift. While most summer days are dry, afternoon thunderstorms are common, particularly during the North American Monsoon in mid and late summer. Some of these summer thunderstorms drop over an inch of rain in a short period, and the lightning can start fires. Summer high temperatures average Winters are comparatively mild, and the temperature is usually only just low enough to sustain a heavy snowpack. For example, Tuolumne Meadows, at 8600 feet (2621 m) elevation, has winter daily highs about with daily lows about The growing season lasts 20 to 230 days, strongly dependent on elevation. Many reservoirs were constructed in the canyons of the Sierra throughout the 20th century, Several major aqueducts serving both agriculture and urban areas distribute Sierra water throughout the state. However, the Sierra casts a rain shadow, which greatly affects the climate and ecology of the central Great Basin. This rain shadow is largely responsible for Nevada being the driest state in the United States. Precipitation varies substantially from year to year. It is not uncommon for some years to receive precipitation totals far above or below normal. The height of the range and the steepness of the Sierra Escarpment, particularly at the southern end of the range, produces a wind phenomenon known as the "Sierra Rotor". This is a horizontal rotation of the atmosphere just east of the crest of the Sierra, set in motion as an effect of strong westerly winds. Because of the large number of airplanes that have crashed in the Sierra Nevada, primarily due to the complex weather and atmospheric conditions such as downdrafts and microbursts caused by geography there, a portion of the area, a triangle whose vertices are Reno, Nevada; Fresno, California; and Las Vegas, Nevada, has been dubbed the "Nevada Triangle", in reference to the Bermuda Triangle. Some counts put the number of crashes in the triangle at 2,000, including millionaire and record breaking flyer Steve Fossett. Hypotheses that the crashes are related in some way to the United States Air Force's Area 51, or to the activities of extra terrestrial aliens, have no evidence to support them.

thumb|Tuolumne Meadows is an example of a subalpine meadow in the Sierra. The Sierra Nevada is divided into a number of biotic zones, each of which is defined by its climate and supports a number of interdependent species. Life in the higher elevation zones adapted to colder weather, and to most of the precipitation falling as snow. The rain shadow of the Sierra causes the eastern slope to be warmer and drier: each life zone is higher in the east. Gray pine (also known as Foothill pine) is intermixed with the oak woodland. west side, east side Washo and Maidu were also in this area prior to the era of European exploration and displacement.

alt=Painting of a lake with deer at the water's edge and the Sierra Nevada in the background. Light is shining between the clouds onto the mountains.|thumb|Albert Bierstadt, Among the Sierra Nevada, California, 1868
American exploration of the mountain range started in 1827. Although prior to the 1820s there were Spanish missions, pueblos (towns), presidios (forts), and ranchos along the coast of California, no Spanish explorers visited the Sierra Nevada. The first Americans to visit the mountains were amongst a group led by fur trapper Jedediah Smith, crossing north of the Yosemite area in May 1827, at Ebbetts Pass. The Walker Party probably visited either the Tuolumne or Merced Groves of giant sequoia, becoming the first non indigenous people to see the giant trees,

Starting in 1841, emigrants from the United States started to move to California via Sonora and Walker Passes. In the winter of 1844, Lt. John C. Frémont, accompanied by Kit Carson, was the first European American to see Lake Tahoe. The Frémont party camped at 2453.64 m.

The Gold Rush populated the western foothills of the Sierra Nevada, but even by 1860, most of the Sierra was unexplored. The state legislature authorized the California Geological Survey to officially explore the Sierra (and survey the rest of the state). Josiah Whitney was appointed to head the survey. Men of the survey, including William H. Brewer, Charles F. Hoffmann and Clarence King, explored the backcountry of what would become Yosemite National Park in 1863. and in 1871, King was the first to climb Mount Langley, mistakenly believing he had summited Mount Whitney, the highest peak in the range. In 1873, Mount Whitney was climbed for the first time by 3 men from Lone Pine, California, on a fishing trip. Before the California Gold Rush, the industry was relatively small, and most of the lumber used in the state was imported. However, as the demand for lumber to support the mining industry increased, logging became a major industry in the region. Initially, most of the lumber produced in California was used in mining. The Comstock Lode was a major center for logging, with operations supplying lumber for the construction of mine structures, such as tunnels, shafts, and buildings, as well as fuel for the mines. Dan DeQuille observed in 1876, "the Comstock Lode may truthfully be said to be the tomb of the forests of the Sierra. Millions upon millions of feet of lumber are annually buried in the mines, nevermore to be resurrected.”

In the late 1800s, the logging industry moved westward due to the depletion of white pine forests in the upper Midwest. This shift was encouraged by the positive portrayal of the Sierra Nevada as a promising timber region. In 1859, Horace Greely marveled, "I never saw anything so much like good timber in the course of any seventy five miles' travel as I saw in crossing the Sierra Nevada." thumb|Clearcutting in Converse Basin resulted in a loss of 8,000 giant sequoia. The logging industry experienced significant growth in the late 1800s due to several factors. The Timber and Stone Act of 1878 allowed individuals to claim ownership of old growth timber tracts, which were later consolidated under joint stock companies, such as those founded by Midwestern lumber magnates. These companies had the financial resources to transport timber from remote locations and build sawmills near the tracks of the Southern Pacific railroad which connected the San Joaquin Valley to the rest of the state in the 1870s. This facilitated the nationwide distribution of lumber. In addition, technological advancements, such as the shay locomotive and the v shaped log flume, made it easier to transport lumber across mountainous terrain. Between 1912 and 1918, Congress debated three times to protect Lake Tahoe in a national park. None of these efforts succeeded, and after World War II, towns such as South Lake Tahoe grew around the shores of the lake. By 1980, the permanent population of the Lake Tahoe area grew to 50,000, while the summer population grew to 90,000. The development around Lake Tahoe affected the clarity of the lake water. In order to preserve the lake's clarity, construction in the Tahoe basin is currently regulated by the Tahoe Regional Planning Agency. As the 20th century progressed, more of the Sierra became available for recreation; other forms of economic activity decreased. The John Muir Trail, a trail that followed the Sierra crest from Yosemite Valley to Mount Whitney, was funded in 1915 and finished in 1938. Kings Canyon National Park was formed in 1940 to protect the deep canyon of the Kings River. In the 1920s, automobile clubs and nearby towns started to lobby for trans Sierra highways over Piute Pass (which would have closed the gap in SR 168) and other locations. However, by end of the 1920s, the Forest Service and the Sierra Club decided that roadless wilderness in the Sierra was valuable, and fought the proposal. The Piute Pass proposal faded out by the early 1930s, with the Forest Service proposing a route over Minaret Summit in 1933. Eventually, a circuitous route across the Sierra was built across Sherman Pass by 1976. By 1964, the Wilderness Act protected portions of the Sierra as primitive areas where humans are simply temporary visitors. Gradually, 20 wilderness areas were established to protect scenic backcountry of the Sierra. These wilderness areas include the John Muir Wilderness (protecting the eastern slope of the Sierra and the area between Yosemite and Kings Canyon Parks), and wilderness within each of the National Parks. The Sierra Nevada still faces a number of issues that threaten its conservation. Logging occurs on both private and public lands, including controversial clearcut methods and thinning logging on private and public lands. Grazing occurs on private lands as well as on National Forest lands, which include Wilderness areas. Overgrazing can alter hydrologic processes and vegetation composition, remove vegetation that serves as food and habitat for native species, and contribute to sedimentation and pollution in waterways. A recent increase in large wildfires like the Rim Fire in Yosemite National Park and the Stanislaus National Forest and the King Fire on the Eldorado National Forest, has prompted concerns. A study looking back over 8,000 years found that warmer climate periods experienced severe droughts and more stand replacing fires and concluded that as climate is such a powerful influence on wildfires, trying to recreate presettlement forest structure may be difficult in a warmer future.