Everything about Yosemite totally explained
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Yosemite National Park (pronounced "yo-SEM-it-ee", ) is a
national park located in the eastern portions of
Tuolumne,
Mariposa and
Madera counties in east central
California,
United States. The park covers an area of 761,266 acres or 1,189 square miles (3,081 km²) and reaches across the western slopes of the
Sierra Nevada mountain chain. Yosemite is
visited by over 3.5 million people each year, many of whom only spend time in the seven square miles (18 km²) of
Yosemite Valley. Almost 95% of the park is designated
wilderness. 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. Two federally designated
Wild and Scenic Rivers, the
Merced and the
Tuolumne, begin within Yosemite's borders and flow westward through the Sierra foothills, 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. 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 don't move, and are therefore not
faults. Spacing between joints is controlled by the amount of
silica in the granite and
granodiorite rocks; more silica tends to create a more resistant rock, resulting in larger spaces between joints and fractures.
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.
Water and ice
Tuolumne and
Merced River systems originate along the crest of the Sierra Nevada in the park and have carved river canyons 3,000 to 4,000 feet (900 to 1,200 m) deep. The Tuolumne River drains the entire northern portion of the park, an area of approximately 680 square miles (1,760 km²). The Merced River begins in the park's southern peaks, primarily the
Cathedral and
Clark Ranges, and drains an area of approximately 511 square miles (1,320 km²).
Hydrologic processes, including
glaciation,
flooding, and fluvial geomorphic response, have been fundamental in creating landforms in the park.
Wetlands in Yosemite occur in valley bottoms throughout the park, and are often hydrologically linked to nearby lakes and rivers through seasonal flooding and groundwater movement.
Meadow habitats, distributed at elevations from 3,000 to 11,000 feet (900 to 3,500 m) in the park, are generally wetlands, as are the
riparian habitats found on the banks of Yosemite's numerous streams and rivers.
Yosemite is famous for its
high concentration of waterfalls in a small area. Numerous sheer drops, glacial steps and
hanging valleys in the park provide many places for
waterfalls to exist, especially during April, May, and June (the snowmelt season). Located in Yosemite Valley, the 2,425-foot-high (739 m)
Yosemite Falls is the highest in
North America. Also in the valley is the much lower volume
Ribbon Falls, which has the highest single vertical drop, 1,612 feet (492 m). None of the Yosemite glaciers are a remnant of the much, much larger
Ice Age alpine glaciers responsible for sculpting the Yosemite landscape. Instead, they were formed during one of the
neoglacial episodes that have occurred since the thawing of the Ice Age (such as the
Little Ice Age).
Global warming has reduced the number and size of glaciers around the world. Many Yosemite glaciers, including Merced Glacier, which was discovered by
John Muir in 1871 and bolstered his glacial origins theory of the Yosemite area, have disappeared and most of the others have lost up to 75% of their surface area. Due to
orographic lift, precipitation increases with elevation up to 8,000 feet (2,400 m) where it slowly decreases to the crest. Precipitation amounts vary from 36 inches (915 mm) at 4,000 feet (1,200 m) elevation to 50 inches (1,200 mm) at 8,600 feet (2,600 m). Snow doesn't typically persist on the ground until November in the high country. It accumulates all winter and into March or early April.
Temperature decreases with increasing elevation. Temperature extremes are moderated by the fact that Yosemite is only about 100 miles (160 km) from the
Pacific Ocean. An anticyclone sits off the coast of California in the summer, sending cool air masses toward the Sierra Nevada that result in clean dry air in the Yosemite area.
Mean daily temperatures range from 25 to 53
°F (-3.9 to 11.5
°C) at Tuolumne Meadows at 8,600 feet (2,600 m). At the Wawona Entrance (elevation 5,130 feet; 1,564 m), mean daily temperature ranges from 36 to 67 °F (2.2 to 19.4 °C). At the lower elevations below 5,000 feet (1525 m), temperatures are hotter; the mean daily high temperature at Yosemite Valley (elevation 3,966 feet; 1,209 m) varies from 46 to 90 °F (7.8 to 32.2 °C). At elevations above 8,000 feet (2,440 m), the hot, dry summer temperatures are moderated by frequent summer
thunderstorms, along with snow that can persist into July. The combination of dry
vegetation, low relative
humidity, and thunderstorms results in frequent
lightning-caused
fires as well.
The
California Gold Rush in the mid-19th century dramatically increased white travel in the area.
United States Army Major
Jim Savage led the
Mariposa Battalion into the west end of Yosemite Valley in 1851 while in pursuit of around 200 Ahwahneechees led by
Chief Tenaya as part of the
Mariposa Wars. Accounts from this battalion were the first confirmed cases of Caucasians entering the valley. Attached to Savage's unit was Dr.
Lafayette Bunnell, the company
physician, who later wrote about his awestruck impressions of the valley in
The Discovery of the Yosemite. Bunnell is credited with naming the valley from his interviews with Chief Tenaya. Bunnell wrote that Chief Tenaya was the founder of the Pai-Ute Colony of Ah-wah-nee. Correspondence and articles written by members of the battalion helped to popularize the valley and surrounding area.
Tenaya and the rest of the Ahwahneechee were eventually captured and their village burned; they were removed to a
reservation near
Fresno, California. Some were later allowed to return to the valley, but got in trouble after attacking a group of eight gold
miners in the spring of 1852. The band fled and took refuge with the nearby
Mono tribe; but after stealing some horses from their hosts, the Ahwahneechees were tracked down and killed by the Monos. A reconstructed "Indian Village of Ahwahnee" is now located behind the Yosemite Museum, which is next to the Yosemite Valley Visitor Center.
Early tourists
Entrepreneur
James Mason Hutchings, artist
Thomas Ayres and two others ventured into the area in 1855, becoming the valley's first tourists. This is the first instance of park land being set aside specifically for preservation and public use by action of the U.S. federal government, and set a precedent for the 1872 creation of
Yellowstone as the first
national park. Yosemite Valley and the Mariposa Grove were ceded to
California as a
state park, and a board of commissioners was proclaimed two years later.
Galen Clark was appointed by the commission as the Grant's first guardian, but neither Clark nor the commissioners had the authority to evict
homesteaders (which included Hutchings). Muir wrote scientific papers on the area's biology.
Increased protection efforts
Overgrazing of
meadows (especially by
sheep),
logging of Giant Sequoia, and other damage caused Muir to become an advocate for further protection. Muir convinced prominent guests of the importance of putting the area under federal protection; one such guest was
Robert Underwood Johnson, editor of
Century Magazine. Muir and Johnson lobbied Congress for the Act that created Yosemite National Park on
October 1 1890. The State of California, however, retained control of the Valley and Grove. Muir also helped persuade local officials to virtually eliminate grazing from the Yosemite High Country.
The newly created national park came under the jurisdiction of the
United States Army's
Fourth Cavalry Regiment on
May 19 1891, which set up camp in Wawona. Automobiles started to enter the park in ever-increasing numbers following the construction of all-weather highways to the park. The Yosemite Museum was founded in 1926 through the efforts of
Ansel Franklin Hall.
In 1903, a dam in the northern portion of the park was proposed. Located in the
Hetch Hetchy Valley, its purpose was to provide water and
hydroelectric power to
San Francisco. Preservationists like Muir and his
Sierra Club opposed the project, while
conservationists like
Gifford Pinchot supported it. In 1913, the U.S. Congress authorized the
O'Shaughnessy Dam through passage of the
Raker Act.
More recently, preservationists persuaded Congress to designate 677,600 acres (2,742 km²), or about 89% of the park, as the
Yosemite Wilderness — a highly protected
wilderness area. The Park Service has reduced artificial inducements to visit the park, such as the
Firefall, in which red-hot embers were pushed off a cliff near
Glacier Point at night.
Traffic congestion in Yosemite Valley during the summer months has become a concern. Plans to exclude all automobiles in the summer that are not registered at a hotel or campground within the valley have been investigated; this would put summer day-use visitors in the valley on a free shuttle bus system, on bicycles, or on foot.
Hotels and concessioners
In the early years of the park, different companies ran multiple hotels and resorts. These resorts included the
Wawona Hotel, the
Yosemite Park Lodge, and
Camp Curry, a tent cabin site in Yosemite Valley. The
Yosemite Park & Curry Company was formed in 1925 to consolidate those often-competing concessions. The Park Service granted the newly formed company exclusive right to operate hotels, restaurants and most stores in Yosemite. Two years later, the new company was headquartered on the mezzanine level of its new hotel, The
Ahwahnee. The Yosemite Park and Curry Company ran the concessions in the park for over 50 years until the company was sold in the late 1970s to United States Natural Resources (USNR) and a couple of years later to MCA which operated Universal Studios. During those ownership changes, the Curry Company name continued. In 1993, MCA was acquired by Matsushita. Then Secretary of the Interior
Manuel Lujan objected to a Japanese firm operating concessions in a U.S. national park, so to avoid delay of federal approval of the acquisition, Matsushita arranged for the sale of the concessions company, ownership of its concession properties was transferred to the federal government, and the Yosemite Park and Curry Co. name was retired. The park concession contract is now operated by
Delaware North Companies "Parks and Resorts" (the official concessionaire name in DNC Parks and Resorts at Yosemite, Inc.).
Geology
Tectonic and volcanic activity
The area of the park was astride a
passive continental margin during the
Precambrian and early
Paleozoic. Later volcanism in the
Jurassic intruded and covered these rocks in what may have been magmatic activity associated with the early stages of the creation of the
Sierra Nevada Batholith. 95% of these rocks were eventually removed by uplifted-accelerated erosion.
The first phase of regional
plutonism started 210 million years ago in the late Triassic and continued throughout the Jurassic to about 150 million years before present (
BP). The second major pluton emplacement phase lasted from about 120 million to 80 million years ago during the
Cretaceous. The streams consequently ran faster and thus cut their valleys more quickly. Additional uplift occurred when major faults developed to the east, especially the creation of
Owens Valley from
Basin and Range-associated extensional forces. Uplift of the Sierra accelerated again about two million years ago during the
Pleistocene.
The uplifting and increased erosion exposed granitic rocks in the area to surface pressures, resulting in
exfoliation (responsible for the rounded shape of the many domes in the park) and mass wasting following the numerous fracture joint planes (cracks; especially vertical ones) in the now solidified plutons. Pleistocene glaciers further accelerated this process and the larger ones transported the resulting
talus and
till from valley floors.
Numerous vertical joint planes controlled where and how fast erosion took place. Most of these long, linear and very deep cracks trend northeast or northwest and form parallel, often regularly spaced sets. They were created by uplift-associated pressure release and by the unloading of overlying rock via erosion.
Sculpting by glaciers
A series of
glaciations further modified the region starting about 2 to 3 million years ago and ending sometime around 10,000
BP. At least four major glaciations have occurred in the Sierra Nevada, locally called the Sherwin (also called the pre-Tahoe), Tahoe, Tenaya, and Tioga.
Biology
Habitats
With habitats ranging from thick foothill
chaparral to expanses of alpine rock, Yosemite National Park supports over 250 species of
vertebrates, which include
fish,
amphibians,
reptiles,
birds, and
mammals. This high diversity of species is also the result of
habitats in Yosemite that are largely intact, compared to areas outside the park where various human activities have resulted in habitat degradation or destruction.
Along much of Yosemite's western boundary, habitats are dominated by mixed
coniferous forests of
Ponderosa Pine,
Sugar Pine,
Incense-cedar,
White Fir, and
Douglas Fir, and a few stands of
Giant Sequoia, interspersed by areas of
Black Oak and
Canyon Live Oak. A relatively high diversity of wildlife species are supported by these habitats, due to relatively mild, lower-elevation
climate and the mixture of habitat types and plant species. Wildlife species typically found in these habitats include
American Black Bear,
Bobcat,
Gray Fox,
Mule deer,
Mountain Kingsnake,
Gilbert's Skink,
White-headed Woodpecker,
Brown Creeper,
Spotted Owl, and a wide variety of
bat species. In the case of bats, large snags are important as roost sites.
Increasing
ozone pollution is causing tissue damage to the massive
Giant Sequoia trees in the park. This makes them more vulnerable to
insect infestation and
disease. Since the
cones of these trees require fire-touched soil to
germinate, historic
fire suppression has reduced these trees' ability to reproduce. The current policy of setting
prescribed fires will hopefully help the germination issue.
Yosemite National Park has documented more than 130 non-native plant
species within park boundaries. These non-native plants were introduced into Yosemite following the migration of early
Euro-American settlers in the late 1850s. Natural and human-caused disturbances, such as wildland fires and construction activities, have contributed to a rapid increase in the spread of non-native plants. A number of these species aggressively invade and displace the native plant communities, resulting in impacts on the park's resources. Non-native plants can bring about significant changes in park ecosystems by altering the native plant communities and the processes that support them. Some non-native species may cause an increase in the fire frequency of an area or increase the available
nitrogen in the soil that may allow more non-native plants to become established. Many non-native species, such as
Yellow Star Thistle (
Centaurea solstitialis), are able to produce a long
tap root that allows them to out-compete the native plants for available water.
Bull Thistle (
Cirsium vulgare),
Common Mullein (
Verbascum thapsus), and
Klamath Weed (
Hypericum perforatum) have been identified as noxious
pests in Yosemite since the 1940s. Additional species that have been recognized more recently as aggressive and requiring control are Yellow Star Thistle,
Sweet Clovers (
Melilotus spp.),
Himalayan Blackberry (
Rubus discolor),
Cut-leaved Blackberry (
Rubus laciniatus) and
Periwinkle (
Vinca major)..
Traffic congestion in the valley is a serious problem during peak season, in summer. A free
shuttle bus system operates year-round in the valley, and
park rangers encourage people to use this system since parking within the valley during the summer is often nearly impossible to find.
In addition to exploring the natural features of the park, visitors can also learn about the
natural and
cultural history of Yosemite at a number of facilities in the valley: the Yosemite Valley Visitor Center, the adjoining Yosemite Museum, and the Nature Center at Happy Isles. There are also two
National Historic Landmarks: the LeConte Memorial Lodge (Yosemite's first public visitor center), and the world-famous
Ahwahnee Hotel.
Hiking
Over 800 miles (1300 km) of trails are available to hikers
Biking
Bicycle rentals are available in Yosemite Valley spring through fall. Over 12 miles of paved bike paths are available in Yosemite Valley. In addition, bicyclists can ride on regular roads.
Helmets are required by law for children under 18 years of age. Off-trail riding and
mountain biking are not permitted in Yosemite National Park.
Driving destinations
While some locations in Yosemite require hiking, other locations can be observed via automobile transportation. Driving locations also allow guests to observe the night sky in locations other than their campsite or lodge. All of the roads in Yosemite are scenic, but the most famous is the
Tioga Road, typically open from late May or early June through November.
As an alternative to driving, bicycles are allowed on the roads. However, bicycles are only allowed off-road on 12 miles of paved trails in Yosemite Valley itself; mountain biking isn't allowed.
Climbing
Rock climbing is an important part of Yosemite.
Camp 4—a walk-in campground in Yosemite Valley—was instrumental in the development of rock climbing as a sport, and is listed on the
National Register of Historic Places. Climbers can generally be spotted in the snow-free months on anything from ten-foot-high (3 m) boulders to the 3,300 foot (1 km) face of
El Capitan. Classes are offered by numerous groups on rock climbing.
Winter activities
Many of the roads in the park close due to heavy snow in winter; however, Yosemite Valley is open all year long.
Downhill skiing is available at the
Badger Pass Ski Area—the oldest downhill skiing area in California, offering downhill skiing from mid-December through early April. Much of the park is open to
cross-country skiing and
snowshoeing, with several backcountry ski huts open for use. Wilderness permits are required for backcountry overnight ski trips.
The
Bracebridge dinner is an annual holiday event, held since 1927 at the
Ahwahnee Hotel, inspired by
Washington Irving's descriptions of Squire Bracebridge and
English Christmas traditions of the 1700s in his
Sketch Book. Between 1929 and 1973, the show was organized by
Ansel Adams.
Further Information
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