| Sierra Nevada | |
| Range | |
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The Sierra's Mills Creek cirque (center) is on the west side of the Sierra Crest, south of Mono Lake (top, blue).
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| Name origin: 1777: Spanish for "snowy mountain range" | |
| Nickname: the Sierra, the High Sierra, the Sierras, Range of Light (1894, John Muir)[1] | |
| Country | United States |
|---|---|
| States | California, Nevada |
| Highest point | Mount Whitney |
| - elevation | 14,505 ft (4,421 m) [2] |
| - coordinates | |
| Length | 400 mi (644 km), north-south from Fredonyer Pass to Tehachapi Pass [3] |
| Width | 65 mi (105 km) [4] |
| Area | 24,370 sq mi (63,118 km2) [5] |
| Geology | batholith, igneous |
| Period | Mesozoic |
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Position of Sierra Nevada inside California
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The Sierra Nevada (Spanish: [ˈsjera neˈβaða], snowy mountain range)[6] is a mountain range in the U.S. states of California and Nevada, between the California Central Valley and the Basin and Range Province. The Sierra runs 400 miles (640 km) north-to-south, and is approximately 70 miles (110 km) across east-to-west. Notable Sierra features include Lake Tahoe, the largest alpine lake in North America; Mount Whitney at 14,505 ft (4,421 m),[2] the highest point in the contiguous United States; and Yosemite Valley sculpted by glaciers out of 100-million-year-old granite. The Sierra is home to three national parks, 20 wilderness areas, and two national monuments. These areas include Yosemite, Sequoia and Kings Canyon National Parks.
The character of the range is shaped by its geology and ecology. More than 100 Ma (million years ago), granite formed deep underground. The range started to uplift 4 Ma, 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, which are reflected by the presence of five life zones.
The Sierra Nevada was home to several Native American tribes. The first European to sight the range was Pedro Fages in 1772.[7] The range was explored between 1844 and 1912.[8]
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The Sierra Nevada stretches from the Susan River[9] and Fredonyer Pass[10] in the north to Tehachapi Pass in the south.[3] It is bounded on the west by California's Central Valley and on the east by the Basin and Range Province. Physiographically, the Sierra is a section of the Cascade-Sierra Mountains province, which in turn is part of the larger Pacific Mountain System physiographic division.
West-to-east, the Sierra Nevada's elevation increases gradually from the California Central Valley to the crest, while the east slope forms the steep Sierra Escarpment. The range is drained on its northwest slopes by the Sacramento River and to the west-southwest by the San Joaquin River, two major Central Valley watercourses that ultimately discharge to the Pacific Ocean. Smaller rivers of the west slope include the Feather, Yuba, American, Mokelumne, Stanislaus and Tuolumne. The southern part of the mountains are drained by four rivers called the Kings, Kaweah, Tule, and Kern. These rivers flow into an endorheic basin called Tulare Lake, but historically joined the San Joaquin during wet years.
To the east, the melting snow of the mountains forms many small rivers that flow out into the Great Basin of Nevada and eastern California. From north to south, the Susan River flows into intermittent Honey Lake; the Truckee River flows from massive Lake Tahoe into Pyramid Lake; the Carson River runs into Carson Sink; the Walker River into Walker Lake; Rush, Lee Vining and Mill Creeks into Mono Lake; and the Owens River into the dry Owens Lake. None of the east-side rivers reach the sea; however, many of the streams from Mono Lake southwards are diverted into the Los Angeles Aqueduct and their water shipped 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 5,000 feet (1,500 m) to more than 9,000 feet (2,700 m). The crest near Lake Tahoe is roughly 9,000 feet (2,700 m) high, with several peaks approaching the height of Freel Peak [10,881 feet (3,317 m)]. Further south, the highest peak in Yosemite National Park is Mount Lyell [13,120 feet (3,999 m)]. The Sierra rise to almost 14,000 feet (4,300 m) with Mount Humphreys near Bishop, California. Finally, near Independence, Mount Whitney is at 14,505 feet (4,421 m), the highest point in the contiguous United States.
South of Mount Whitney, the range quickly dwindles. The crest elevation is almost 10,000 feet (3,000 m) near Lake Isabella, but south of the lake, the peaks reach only to a modest 8,000 feet (2,400 m).[11]
There are several notable geographical features in the Sierra Nevada:
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.[14] In the Triassic and into the Jurassic, an island arc collided with the west coast of North America and raised a set of mountains, in an event called the Nevadan orogeny.[15]
In the Cretaceous, a subduction zone formed at the edge of the continent.[16] 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.[17] The earlier plutons formed in the western half of the Sierra, while the later plutons formed in the eastern half of the Sierra.[14] By 65 Ma, the proto-Sierra Nevada had been worn down to a range of rolling low mountains, a few thousand feet high.
Twenty million years ago, crustal extension associated with the Basin and Range Province caused extensive volcanism in the Sierra.[18] About 4 Ma, the Sierra Nevada started to form: a block of crust between the Coast Range and the Basin and Range Province started to 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 Ma. 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.[19]
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 20 to 80 in (510 to 2,000 mm) where it occurs mostly as snow above 6,000 ft (1,800 m). Summers are dry with low humidity; however, afternoon thunderstorms are not uncommon, particularly during the North American Monsoon. Summer high temperatures average 42–90 °F (6–32 °C). The growing season lasts 20 to 230 days, strongly dependent on elevation.[20]
The Sierra Nevada snowpack is the major source of water and a significant source of electric power generation in California.[21] 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.[22]
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 Sierras, set in motion as an effect of strong westerly winds.[23]
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.[17] 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.[17] A list of biotic zones, and corresponding elevations, is presented below:
Archaeological excavations placed Martis people of Paleo-Indians in northcentral Sierra Nevada during the period of 3,000 BCE to 500 CE. The earliest identified sustaining indigenous people in the Sierra Nevada were the Northern Paiute tribes of Native American on the east side, with the Mono tribe and Sierra Miwok tribe on the western side, and the Kawaiisu tribe in the southern Sierra. Today, some mountain passes, such as Duck Pass with obsidian arrowheads, are artifact locations from historic intertribal trade route trails. The California and Sierra Native American tribes were predominantly peaceful, with occasional territorial disputes between the Paiute and Sierra Miwok tribes in the mountains.[25] Washo and Maidu were also in this area prior to the era of European exploration and displacement.[26][27]
Used in 1542 by Juan Rodriguez 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,[28] In 1777, Pedro Font's map applied the name to the range currently known as the Sierra Nevada.[29]
The literal translation is "snowy mountains," from sierra "a range of hills," 1610s, from Spanish sierra "jagged mountain range," lit. "saw," from Latin serra "a saw"; and from fem. of Spanish nevado "snowy."[30][31]
European-American exploration of the mountain range started in the 1840s. In the winter of 1844, Lt. John C. Frémont, accompanied by Kit Carson, was the first European to see Lake Tahoe. The Frémont party camped at 8,050 ft (2,450 m).[32]
By 1860, California Gold Rush populated the flanks of the Sierra Nevada, leaving most of the Sierra unexplored.[33][34] 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.[33] In 1864 they explored the area around Kings Canyon. In 1869, John Muir started his wanderings in the Sierra Nevada range,[35] and in 1871 King was the first to climb Mount Langley and that year fishermen were the first to climb Mount Whitney.[33] From 1892–7 Theodore Solomons made the first attempt to map a route along the crest of the Sierra.[33]
Other people finished exploring and mapping the Sierra. Bolton Coit Brown explored the Kings River watershed in 1895–1899. Joseph N. LeConte mapped the area around Yosemite National Park and what would become Kings Canyon National Park. James S. Hutchinson, a noted mountaineer, climbed the Palisades (1904) and Mount Humphreys (1905). By 1912, the USGS published a set of maps of the Sierra Nevada, and the era of exploration was over.[8]
The tourism potential of the Sierra Nevada was recognized early in the European history of the range. Yosemite Valley was first protected by the federal government in 1864. The Valley and Mariposa Grove were ceded to California in 1866 and turned into a state park.[36] John Muir perceived overgrazing by sheep and logging of Giant Sequoia to be a problem in the Sierra. Muir successfully lobbied for the protection of the rest of Yosemite National Park: Congress created an Act to protect the park in 1890. The Valley and Mariposa Grove were added to the Park in 1906.[36] In the same year, Sequoia National Park was formed to protect the Giant Sequoia: all logging of the Sequoia ceased at that time.
In 1903, the city of San Francisco proposed building a hydroelectric dam to flood Hetch Hetchy Valley. The city and the Sierra Club argued over the dam for 10 years, until the U.S. Congress passed the Raker Act in 1913 and allowed dam building to proceed. O'Shaughnessy Dam was completed in 1923.[37][38]
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.[39] 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.[40]
As the twentieth 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.[41] Kings Canyon National Park was formed in 1940 to protect the deep canyon of the Kings River.
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.
Today, much of the Sierra Nevada is owned by the U.S. Federal government and is either protected from development or is strictly managed. The three National Parks (Yosemite, Kings Canyon, Sequoia), two National Monument (Devils Postpile, Giant Sequoia), and 20 wilderness areas lie within the Sierra. These areas protect 15.4% of the Sierra's 63,118 km2 (24,370 sq mi) from logging and grazing.[5]
The United States Forest Service and the Bureau of Land Management currently control 52% of the land in the Sierra Nevada.[5] Logging and grazing is generally allowed on land controlled by these agencies, under federal regulations that balance recreation and development on the land.
The California Bighorn Sheep Zoological Area near Mount Williamson in the southern Sierra was established to protect the endangered Sierra Nevada Bighorn Sheep. Starting in 1981, hikers were unable to enter the Area from May 15 through December 15, in order to protect the sheep. As of 2010, the restriction has been lifted and access to the Area is open for the whole year.[42]
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