Wolfgang Staudt
Yosemite National Park
Yosemite National Park is a national park largely in Mariposa County, and Tuolumne County, California, United States. The park covers an area of 1,189 mi² (3,081 km²) and reaches across the western slopes of the Sierra Nevada mountain chain. Yosemite is visited by over 3 million visitors each year, with most only seeing Yosemite Valley. Designated a World Heritage Site in 1984, Yosemite is internationally recognized for its spectacular granite cliffs, waterfalls, clear streams, Giant Sequoia groves, and biological diversity (about 89% of the park is designated wilderness area). It was also the first park set aside by the U.S. federal government. Although not the first designated national park, Yosemite was a focal point in the development of the national park idea, largely owing to the work of people like John Muir.
Yosemite is one of the largest and least fragmented habitat blocks in the Sierra Nevada, and it supports a diversity of plants and animals. The park has an elevation range from 2,000 to 13,114 feet (600 to 4000 m) and contains five major vegetation zones: chaparral/oak woodland, lower montane, upper montane, subalpine and alpine. Of California's 7,000 plant species, about 50% occur in the Sierra Nevada and more than 20% within Yosemite. There is suitable habitat or documented records for more than 160 rare plants in the park, with rare local geologic formations and unique soils characterizing the restricted ranges many of these plants occupy.
The geology of the Yosemite area is characterized by granitic rocks and remnants of older rock. About 10 million years ago, the Sierra Nevada was uplifted and then tilted to form its relatively gentle western slopes and the more dramatic eastern slopes. The uplift increased the steepness of stream and river beds, resulting in formation of deep, narrow canyons. About 1 million years ago, snow and ice accumulated, forming glaciers at the higher alpine meadows that moved down the river valleys. Ice thickness in Yosemite Valley may have reached 4,000 feet (1200 m) during the early glacial episode. The downslope movement of the ice masses cut and sculpted the U-shaped valley that attracts so many visitors to its scenic vistas today.
Geography
Yosemite National Park is located in the central Sierra Nevada of California. It takes 3.5 hours to drive to the park from San Francisco and about six hours from Los Angeles. Yosemite is surrounded by wilderness areas: the Ansel Adams Wilderness to the southeast, the Hoover Wilderness to the northeast, and the Emigrant Wilderness to the north.
The 1,200-square-mile (3,100 km²) park contains thousands of lakes and ponds, 1,600 miles (2,600 km) of streams, 800 miles (1300 km) of hiking trails, and 350 miles (560 km) of roads. Two federally designated wild and scenic rivers, the Merced and Tuolumne, begin within Yosemite's borders and flow west into the Central Valley of California. Annual park visitation exceeds 3.5 million, with most visitor use concentrated in the seven square mile (18 km²) area of Yosemite Valley.
Rocks and erosion
Almost all of the landforms in the Yosemite area are cut from the granitic rock of the Sierra Nevada Batholith (a batholith is a large mass of intrusive igneous rock that formed deep below the surface). About 5% of the park (mostly in its eastern margin near Mount Dana) are from metamorphosed volcanic and sedimentary rocks. These rocks are called "roof pendants" because they were once the roof of the underlying granitic rock.
Erosion acting upon different types of uplift-created joint and fracture systems is responsible for creating the valleys, canyons, domes, and other features we see today (these joints and fracture systems do not move, and are therefore not faults). Spacing between joints and fracture systems is largely due to the amount of silica in the granite and granodiorite rocks; more silica tends to create larger spaces between joints and fractures and thus a more resistant rock.
Pillars and columns, such as Washington Column and Lost Arrow, are created by cross joints. Erosion acting on master joints is responsible for creating valleys and later canyons. The single most erosive force over the last few million years has been from large alpine glaciers, which have turned the previously V-shaped river-cut valleys into U-shaped glacial-cut canyons (such as Yosemite Valley and Hetch Hetchy Valley). Exfoliation (caused by the tendency of crystals in plutonic rocks to expand at the surface) acting on granitic rock with widely spaced joints is responsible for creating domes such as Half Dome and North Dome and inset arches like Royal Arches.
Popular features
Yosemite Valley represents only one percent of the park area, but this is where most visitors arrive and stay. El Capitan, a prominent granite cliff that looms over the valley, is one of the most popular world destinations for rock climbers because of its diverse range of difficulties and numerous established climbing routes in addition to its year-round accessibility. Impressive granite domes such as Sentinel Dome and Half Dome rise 3,000 feet and 4,800 feet (900 and 1450 m), respectively, above the valley floor.
The high country of Yosemite contains beautiful areas, such as Tuolumne Meadows, Dana Meadows, the Clark Range, the Cathedral Range, and the Kuna Crest. The Sierra crest and the Pacific Crest Trail run through Yosemite, with peaks of red metamorphic rock, such as Mount Dana and Mount Gibbs, and granite peaks, such as Mount Conness. Mount Lyell is the highest point in the park.
The park has three groves of ancient Giant Sequoia (Sequoiadendron giganteum) trees; the Mariposa Grove (200 trees), Tuolumne Grove (25 trees), and the Merced Grove (20 trees). Giant Sequoia are the most massive trees in the world and are one of the tallest and longest-lived (Coast Redwoods that live along the Northern Californian coast are the tallest and the Great Basin Bristlecone Pine of Eastern California are the oldest). These trees were much more widespread before the start of the last Ice Age (Geology of U.S. Parklands, page 227).
From Wikipedia, the free encyclopedia
Yosemite National Park
Yosemite National Park is a national park largely in Mariposa County, and Tuolumne County, California, United States. The park covers an area of 1,189 mi² (3,081 km²) and reaches across the western slopes of the Sierra Nevada mountain chain. Yosemite is visited by over 3 million visitors each year, with most only seeing Yosemite Valley. Designated a World Heritage Site in 1984, Yosemite is internationally recognized for its spectacular granite cliffs, waterfalls, clear streams, Giant Sequoia groves, and biological diversity (about 89% of the park is designated wilderness area). It was also the first park set aside by the U.S. federal government. Although not the first designated national park, Yosemite was a focal point in the development of the national park idea, largely owing to the work of people like John Muir.
Yosemite is one of the largest and least fragmented habitat blocks in the Sierra Nevada, and it supports a diversity of plants and animals. The park has an elevation range from 2,000 to 13,114 feet (600 to 4000 m) and contains five major vegetation zones: chaparral/oak woodland, lower montane, upper montane, subalpine and alpine. Of California's 7,000 plant species, about 50% occur in the Sierra Nevada and more than 20% within Yosemite. There is suitable habitat or documented records for more than 160 rare plants in the park, with rare local geologic formations and unique soils characterizing the restricted ranges many of these plants occupy.
The geology of the Yosemite area is characterized by granitic rocks and remnants of older rock. About 10 million years ago, the Sierra Nevada was uplifted and then tilted to form its relatively gentle western slopes and the more dramatic eastern slopes. The uplift increased the steepness of stream and river beds, resulting in formation of deep, narrow canyons. About 1 million years ago, snow and ice accumulated, forming glaciers at the higher alpine meadows that moved down the river valleys. Ice thickness in Yosemite Valley may have reached 4,000 feet (1200 m) during the early glacial episode. The downslope movement of the ice masses cut and sculpted the U-shaped valley that attracts so many visitors to its scenic vistas today.
Geography
Yosemite National Park is located in the central Sierra Nevada of California. It takes 3.5 hours to drive to the park from San Francisco and about six hours from Los Angeles. Yosemite is surrounded by wilderness areas: the Ansel Adams Wilderness to the southeast, the Hoover Wilderness to the northeast, and the Emigrant Wilderness to the north.
The 1,200-square-mile (3,100 km²) park contains thousands of lakes and ponds, 1,600 miles (2,600 km) of streams, 800 miles (1300 km) of hiking trails, and 350 miles (560 km) of roads. Two federally designated wild and scenic rivers, the Merced and Tuolumne, begin within Yosemite's borders and flow west into the Central Valley of California. Annual park visitation exceeds 3.5 million, with most visitor use concentrated in the seven square mile (18 km²) area of Yosemite Valley.
Rocks and erosion
Almost all of the landforms in the Yosemite area are cut from the granitic rock of the Sierra Nevada Batholith (a batholith is a large mass of intrusive igneous rock that formed deep below the surface). About 5% of the park (mostly in its eastern margin near Mount Dana) are from metamorphosed volcanic and sedimentary rocks. These rocks are called "roof pendants" because they were once the roof of the underlying granitic rock.
Erosion acting upon different types of uplift-created joint and fracture systems is responsible for creating the valleys, canyons, domes, and other features we see today (these joints and fracture systems do not move, and are therefore not faults). Spacing between joints and fracture systems is largely due to the amount of silica in the granite and granodiorite rocks; more silica tends to create larger spaces between joints and fractures and thus a more resistant rock.
Pillars and columns, such as Washington Column and Lost Arrow, are created by cross joints. Erosion acting on master joints is responsible for creating valleys and later canyons. The single most erosive force over the last few million years has been from large alpine glaciers, which have turned the previously V-shaped river-cut valleys into U-shaped glacial-cut canyons (such as Yosemite Valley and Hetch Hetchy Valley). Exfoliation (caused by the tendency of crystals in plutonic rocks to expand at the surface) acting on granitic rock with widely spaced joints is responsible for creating domes such as Half Dome and North Dome and inset arches like Royal Arches.
Popular features
Yosemite Valley represents only one percent of the park area, but this is where most visitors arrive and stay. El Capitan, a prominent granite cliff that looms over the valley, is one of the most popular world destinations for rock climbers because of its diverse range of difficulties and numerous established climbing routes in addition to its year-round accessibility. Impressive granite domes such as Sentinel Dome and Half Dome rise 3,000 feet and 4,800 feet (900 and 1450 m), respectively, above the valley floor.
The high country of Yosemite contains beautiful areas, such as Tuolumne Meadows, Dana Meadows, the Clark Range, the Cathedral Range, and the Kuna Crest. The Sierra crest and the Pacific Crest Trail run through Yosemite, with peaks of red metamorphic rock, such as Mount Dana and Mount Gibbs, and granite peaks, such as Mount Conness. Mount Lyell is the highest point in the park.
The park has three groves of ancient Giant Sequoia (Sequoiadendron giganteum) trees; the Mariposa Grove (200 trees), Tuolumne Grove (25 trees), and the Merced Grove (20 trees). Giant Sequoia are the most massive trees in the world and are one of the tallest and longest-lived (Coast Redwoods that live along the Northern Californian coast are the tallest and the Great Basin Bristlecone Pine of Eastern California are the oldest). These trees were much more widespread before the start of the last Ice Age (Geology of U.S. Parklands, page 227).
From Wikipedia, the free encyclopedia