Yosemite National Park

Yosemite
Designation	National park
Location	California USA
Nearest City	Modesto, California
Coordinates	Template:Coor dm
Area	761,266 acres 3080.73 km²
Date of Establishment	September 25 1890
Visitation	3,380,038 (2003)
Governing Body	National Park Service
IUCN category	Ib (Wilderness Area) II (National Park)

Yosemite National Park (pronounced "Yo-SEM-it-tee", IPA ) is a U.S. 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 stretches across the western slopes of the Sierra Nevada mountain range. Over 3 million people visit Yosemite 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 95% of the park is designated wilderness area). It was also the first park set aside by the U.S. federal government and through the work of people like John Muir was a focal point in the development of the national park idea.

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 13,123 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.

Contents

1 Geography 1.1 Rocks and erosion 1.2 Popular features 1.3 Water and ice 1.4 Climate 2 History 2.1 The Ahwahnechee and the Mariposa Wars 2.2 Early tourists 2.3 The Yosemite Grant 2.4 Increased protection efforts 2.5 Later history 3 Geology 3.1 Tectonic and volcanic activity 3.2 Uplift and erosion 3.3 Sculpting by glaciers 4 Biology 4.1 Habitats 4.2 Management issues 5 Activities 5.1 Hiking 5.2 Climbing 5.3 Summer activities 5.4 Winter activities 6 References 7 External links

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 once much more widespread before the last Ice Age began (Geology of U.S. Parklands, page 227).

Half Dome from North Dome	Mariposa Grove	Tenaya Lake	Mount Dana

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 1200 m) deep. The Tuolumne River drains the entire northern portion of the park, an area of approximately 680 square miles (1760 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 (1320 km²).

Hydrologic processes, including glaciation, flooding, and fluvial geomorphic response, have been fundamental in creating landforms in the park. The park also contains approximately 3,200 lakes (greater than 100 square meters), two reservoirs, and 1,700 miles (2700 km) of streams, all of which help form these two large watersheds. 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 3500 m) in the park, are generally wetlands, as are the riparian habitats found on the banks of Yosemite's numerous streams and rivers.

Numerous sheer drops, glacial steps and hanging valleys in the park provide many places for waterfalls to exist, especially during during April, May, and June (the snowmelt season). Located in Yosemite Valley, the 2425 foot (782 m) high Yosemite Falls is the highest in North America and the third highest in the world. Also in the valley is the much lower volume Ribbon Falls, which has the highest single vertical drop, 1612 feet (492 m) (Geology of U.S. Parklands, page 227). Perhaps the most prominent of the Yosemite waterfalls is Bridalveil Fall, which is the waterfall seen from the Tunnel View viewpoint at the east end of the Wawona Tunnel. Wapama Falls in Hetch Hetchy Valley is another notable waterfall.

All glaciers in the park are relatively small glaciers that occupy areas that are in almost permanent shade, such as north and northeast facing cirques. Lyell Glacier is the largest glacier in the Sierra Nevada (and therefore the park) and covers 160 acres (65 ha). None of the Yosemite glaciers are the remnants 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 (Geology of U.S. Parklands, page 228).

Climate

The area of the park has a Mediterranean climate, meaning almost all yearly precipitation normally falls during mild winter and the other seasons are nearly dry (less than 3% of precipitation falls in the typically long, hot summers). Due to orographic lift precipitation increases with elevation until around 8000 feet (2400 m) when it slowly decreases to the crest. Precipitation amounts vary from 36 inches (915 mm) at 4,000 feet (1200 m) elevation to 50 inches (1200 mm) at 8,600 feet (2600 m). Snow does not 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 South Entrance near Wawona (elevation 6192 feet; 1887 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; 1209 m) varies from 46 to 90 °F (7.8 to 32.2 °C). At elevations above 8,000 feet (2440 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.

History

Main article: History of the Yosemite area

The Ahwahnechee and the Mariposa Wars

Miwok and Paiute peoples lived in the area for decades before the first white explorations into the region. A band of Miwok called the Ahwahnechee lived in Yosemite Valley when the first Caucasians entered it.

The California Gold Rush in the mid-19th century dramatically increased white travel in the area. United States Army Major James Savage led the Mariposa Battalion into Yosemite Valley in 1851 while in pursuit of around 200 Ahwaneechees 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. Bunnel is credited with naming the valley after what he thought was the name of the band they were pursing. 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 miners in 1852. The band fled to take refuge with the nearby Mono tribe, which betrayed its hospitality—each Ahwahneechee was tracked down and killed by the Mono.

Early tourists

Entrepreneur James Mason Hutchings, artist Thomas Ayres, and two others ventured into the area in 1855, becoming the valley's first tourists. Hutchings wrote articles and books about this and later excursions in the area and Ayres' scretchs became the first accurate drawings of many prominent features. Photographer Charles Leander Weed took the first photographs of the Valley's features in 1859. Later photographers included Ansel Adams.

Wawona was an Indian encampment in what is now the south-western part of the park. Settler Galen Clark discovered the Mariposa Grove of Giant Sequoia in Wawona in 1856. Simple lodgings were built, as were roads to the area. In 1879, the Wawona Hotel was built to serve tourists visiting the Grove. As tourism increased, so did the number of trails and hotels.

The Yosemite Grant

Concerned by the effects of commercial interests, several prominent people advocated for protection of the area. A park bill passed both houses of the U.S. Congress and was signed by President Abraham Lincoln on June 30, 1864, creating the Yosemite Grant. 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). The issue was not settled until 1875 when the land holdings were invalidated. Clark and the reigning commissioners were ousted in 1880 and Hutchings became the new park guardian.

Access to the park by tourists improved in the early years of the park and conditions in the Valley were made more hospitable. Tourism started to significantly increase after the First Transcontinental Railroad was completed in 1869, but the long horseback ride needed to reach the area was a deterrent. Three stagecoach roads were built in the mid-1870s to provide better access to the growing number of visitors to the Valley.

Scottish-born naturalist John Muir first wrote many articles popularizing the area and increasing scientific interest in it. Muir was one of the first to theorize that the major landforms in Yosemite were created by large alpine glaciers, bucking established scientists such as Josiah Whitney, who regarded Muir as an amateur. Muir also wrote scientific papers on the area's biology.

Increased protection efforts

Over-grazing 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. Through Johnson, he was able to help pass an act of Congress 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. By the late 1890s, sheep grazing was no longer a problem and the Army made many other improvements. The Cavalry could not intervene to help the worsening condition of the Valley or Grove.

Muir and his Sierra Club continued to lobby the government and influential people for the creation of a unified Yosemite National Park. Then, in May of 1903, Theodore Roosevelt, who was then President of the United States, camped with John Muir near Glacier Point for three days. On that trip, Muir convinced Roosevelt to take control of the Valley and the Grove away from California and give it to the federal government. In 1906, Roosevelt signed a bill that did precisely that.

Later history

The National Park Service was formed in 1916 and Yosemite was transferred to that agency's jurisdiction. Tuolumne Meadows Lodge, Tioga Pass Road, and campgrounds at Tenaya and Merced lakes were also completed in 1916. Automobiles started to enter the park in ever-increasing numbers following the construction of all-weather highways to the park.

To the north of Yosemite Valley but within the park is Hetch Hetchy Valley, which was slated for flooding to create a reservoir and hydroelectric power plant to benefit far-away San Francisco. A nationally polarized fight ensued, pitting preservationists like Muir and his Sierra Club against conservationists like Gifford Pinchot. The U.S. Congress eventually authorized the O'Shaughnessy Dam in 1913 through passage of the Raker Act.

Since then, preservationists have convinced Congress to set aside about 95% of the park in a highly protected wilderness area. The Park Service has also been moving away from allowing touristy inducements to visit the park, such as the famous Firefall (in which red hot embers were pushed off a cliff near Glacier Point at night). Increasing traffic congestion in Yosemite Valley during the summer months has also been an issue of concern. Proposals to exclude all automobiles in the summer that are not registered at a hotel or campground within the valley have been investigated. This would force all summer day use visitors in the valley to use the free shuttle system, bike, or walk in the 7 mile (11 km) long valley.

Geology

Main article: Geology of the Yosemite area

Tectonic and volcanic activity

The area of the park was astride a passive continental margin during the Precambrian and early Paleozoic. Sediment was derived from continental sources and was deposited in shallow water. These rocks have since been metamorphosed.

Heat generated from the Farallon Plate subducting below the North American Plate led to the creation of an island arc of volcanoes on the west coast of proto-North America between the late Devonian and Permian periods. 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). Around the same time, the Nevadan orogeny built the Nevadan mountain range (also called the Ancestral Sierra Nevada) to a height of 15,000 feet (4500 m). This was directly part of the creation of the Sierra Nevada Batholith, and the resulting rocks were mostly granitic in composition and emplaced about 6 miles (10 km) below the surface. The second, major pluton emplacement phase lasted from about 120 million to 80 million years ago during the Cretaceous. This was part of the Sevier orogeny.

Starting 20 million years ago (in the Cenozoic) and lasting until 5 million years ago a now-extinct extension of Cascade Range volcanoes erupted, bringing large amounts of igneous material in the area. These igneous deposits blanketed the region north of the Yosemite region. Volcanic activity persisted past 5 million years BP east of the current park borders in the Mono Lake and Long Valley areas.

Uplift and erosion

Starting 10 million years ago, vertical movement along the Sierra fault started to uplift the Sierra Nevada. Subsequent tilting of the Sierra block and the resulting accelerated uplift of the Sierra Nevada increased the gradient of western-flowing streams. The streams consequently ran faster and thus cut their valleys more quickly (most notably in Yosemite Valley). 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 4 major glaciations have occurred in the Sierra Nevada; locally called the Sherwin (also called the pre-Tahoe), Tahoe, Tenaya, and Tioga. The Sherwin glaciers were the largest, filling Yosemite and other valleys, while later stages produced much smaller glaciers. A Sherwin-age glacier was almost surely responsible for the major excavation and shaping of Yosemite Valley and other canyons in the area.

Glacial systems reached depths of up to 4000 feet (1200 m) and left their marks in the Yosemite area. The longest glacier in the Yosemite area ran down the Grand Canyon of the Tuolumne River for 60 miles (95 km), passing well beyond Hetch Hetchy Valley. Merced Glacier flowed out of Yosemite Valley and into the Merced River Gorge. Lee Vining Glacier carved Lee Vining Canyon and emptied into Lake Russel (the much enlarged ice age version of Mono Lake). Only the highest peaks, such as Mount Dana and Mount Conness, were not covered by glaciers. Retreating glaciers often left recessional moraines that impounded lakes such as Lake Yosemite (a shallow lake that periodically covered much of the floor of Yosemite Valley).

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 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.

Going higher in elevation, the coniferous forests become purer stands of Red Fir, Western White Pine, Jeffrey Pine, Lodgepole Pine, and the occasional Foxtail pine. Fewer wildlife species tend to be found in these habitats, due to their higher elevation, and lower complexity. Species likely to be found include Golden-mantled Ground Squirrel, Chickaree, Marten, Steller's Jay, Hermit Thrush, and Northern Goshawk. Reptiles are not common, but include Rubber Boa, Western Fence Lizard, and Northern Alligator Lizard.

As the landscape rises, trees become smaller and more sparse, with stands broken by areas of exposed granite. These include Lodgepole Pine, Whitebark Pine, and Mountain Hemlock that, at highest elevations, give way to vast expanses of granite as treeline is reached. The climate in these habitats is harsh and the growing season is short, but species such as Pika, Yellow-bellied Marmot, White-tailed Jackrabbit, Clark's Nutcracker, and Rosy Finch are adapted to these conditions. Also, the treeless alpine habitats are the areas favored by Sierra Nevada Bighorn Sheep. This species, however, is now found in the Yosemite area only around Tioga Pass, where a small, reintroduced population exists.

At a variety of elevations, meadows provide important, productive habitat for wildlife. Animals come to feed on the green grasses and use the flowing and standing water found in many meadows. Predators, in turn, are attracted to these areas. The interface between meadow and forest is also favored by many animal species because of the proximity of open areas for foraging and cover for protection. Species that are highly dependent upon meadow habitat include Great Gray Owl, Willow Flycatcher, Yosemite Toad, and Mountain Beaver.

See also: Biology of the Sierra Nevada

Management issues

Despite the richness of high-quality habitats in Yosemite, three species have become extinct in the park within historical time, and another 37 species currently have special status under either California or federal endangered species legislation. The most serious current threats to Yosemite's wildlife and the ecosystems they occupy include loss of a natural fire regime, exotic species, air pollution, habitat fragmentation, and climate change. On a more local basis, factors such as road kills and the availability of human food have affected some wildlife species.

The black bears of Yosemite were once famous for breaking into parked cars to steal food. They were also an encouraged tourist sight for many years at the park's garbage dumps, where bears congregated to eat park visitors' garbage and tourists gathered to photograph the bears. Increasing encounters between bears and humans and increasing damage to property led to an aggressive campaign to discourage bears from relying on human food or interacting with people and their property. The open-air dumps were closed; all trash receptacles were replaced with bear-proof receptacles; all campgrounds were equipped with bear-proof food lockers so that people would not leave food in their vehicles, which were easy targets for the powerful and resourceful bears. Because bears who show aggression towards people usually must eventually be destroyed, park personnel have continued to come up with innovative ways to have bears associate humans and their property with unpleasant experiences, such as being hit with rubber bullets. Today, about 30 bears a year are captured and ear-tagged and their DNA is sampled so that, when bear damage occurs, rangers can ascertain which bear is causing the problem.[1] (http://news.nationalgeographic.com/news/2001/04/0423_wirebears.html)

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. [2] (http://www.nps.gov/yose/nature/veg_exotics.htm)

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). Physical removal efforts along with the use of prescribed fires are being used to combat this problem.

Activities

Yosemite Valley is open year-round but much of the rest of the park is closed due to snow in late fall and does not open until mid to late spring. Open-air tours around Yosemite Valley and the Mariposa Grove of Giant Sequoias are available. Many people enjoy short walks and longer hikes to waterfalls in Yosemite Valley or walks amongst Giant Sequoias in the Mariposa, Tuolumne, or Merced Groves. Others like to drive or take a tour bus to Glacier Point (summer-fall) to see a spectacular view of Yosemite Valley and the high country or drive along the scenic Tioga Road to Tuolumne Meadows (summer-fall) and go for a walk or hike.

Most people who enter the park only stay for the day and only visit locations within Yosemite Valley that are easily accessible via their automobile (as of 2005 there is a US$20 fee per automobile to enter the park). Traffic congestion in the valley is therefore a serious problem during the peak visitation season, 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 summer is very often not possible to find. Almost all the park, however, is highly protected roadless wilderness that does not allow any motorized vehicles and requires permits for overnight stays (many restrictions apply, rangers will inform you of these).

Hiking

Over 800 miles (1300 km) of trails are available to hikers—anything from the easy stroll, to the grueling hikes up several park mountains, to multiple-day backpack trips.

The park is best divided into 5 sections for the day-user—Yosemite Valley, Wawona/Mariposa Grove/ Glacier Point, Tuolumne Meadows, Hetch Hetchy, and Crane Flat/White Wolf. Numerous books describe park trails, and free information is available from the Park Service in Yosemite. There are also many free resources on the Internet that contain hiking recommendations and advice on Yosemite trails. Most park workers strongly encourage guests to experience portions of the park other than Yosemite Valley.

Climbing

Rock climbing is an important part of Yosemite. Camp 4—a walk-in campground in Yosemite Valley—has been said to be one of the most important places in the world to the history of rock climbing. Climbers can generally be spotted in the snow-free months on anything from ten foot (3 m) high boulders to the 3,300 foot (1 km) face of El Capitan. Classes are offered by numerous groups on rock climbing.

Summer activities

• Backpacking - Between late spring and early fall, much of the park is open to multiple-day backpack trips. All overnight trips into the back country require a wilderness permit and most require approved bear-resistant food storage. The park wilderness office can provide more information.

• Bicycling - Yosemite Valley contains more than 15 miles (24 km) of bike trails. Under Park Service regulations, bikes are allowed only on paved areas. Mountain biking is not allowed in Yosemite National Park.

• Swimming/Rafting - Generally about midsummer, the Merced River in Yosemite Valley becomes warm enough and is still deep enough to raft down substantial portions. For those who don't like the cold water, a few heated pools are available.

• Horseback riding - Stables are open in the summer, offering guided rides (generally by mule). Public stables are present in Yosemite Valley, Wawona, and Tuolumne Meadows. Many operations outside Yosemite ride horses into the park. Horses are allowed in many sections of the "backcountry"; however, rangers advise visitors to check with the park wilderness office for more info.

Winter activities

Much of the park closes due to heavy snow in winter. However, Yosemite Valley is open all year long.

• Skiing - Badger Pass Ski Area (the oldest ski area in California) opens in winter. Skiing is not up to par with Lake Tahoe or Colorado resorts, but has its own charm, being in Yosemite. The are several downhill runs and a ski school. Much of the park is open to cross-country skiing, with several backcountry ski huts open for use. Wilderness permits are required for backcountry overnight ski trips.

• Snowshoeing - Also known as winter hiking, snowshoes are commonly used to experience portions of Yosemite. Many guided snowshoe walks are conducted in winter by the Park Service and by other organizations

• Ice skating - The Curry Village ice rink is open between November and March. Now smaller than its historical size, the rink still offers room for the figure skaters and those with poor balance. The rink runs 2-to-3-hour sessions and cleans the ice between sessions.

• Bracebridge dinner - 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.

References

• Geology of National Parks: Fifth Edition, Ann G. Harris, Esther Tuttle, Sherwood D., Tuttle (Iowa, Kendall/Hunt Publishing; 1997) ISBN 0-7872-5353-7
• Yosemite: A Visitor's Companion, George Wuerthner, (Stackpole Books; 1994) ISBN 0-8117-2598-7
• Geology of U.S. Parklands: Fifth Edition, Eugene P. Kiver and David V. Harris (Jonh Wiley & Sons; New York; 1999; page 227) ISBN 0-471-33218-6
• Yosemite: Official National Park Service Handbook (no. 138), Division of Publiations, National Park Service
• Yosemite National Park: A Natural History Guide to Yosemite and Its Trails, Jeffrey P. Schaffer, (Wilderness Press, Berkeley; 1999) ISBN 0-89997-244-6
• National Park Service: Yosemite Wildlife [3] (http://www.nps.gov/yose/nature/veg_exotics.htm), [4] (http://www.nps.gov/yose/nature/wildlife.htm), [5] (http://www.nps.gov/yose/nature/nature.htm), [6] (http://www.nps.gov/yose/nature/water.htm), [7] (http://www.nps.gov/yose/nature/wtr_climate.htm) (adapted public domain text)

See also: List of guidebooks about the Sierra Nevada

External links

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• Official site: Yosemite National Park (http://www.nps.gov/yose)
• The Yosemite Association (http://www.yosemite.org)
• The Yosemite Institute (http://www.yni.org/yi)
• QTVRs of Yosemite National Park at virtualparks.org (http://www.virtualparks.org/parks/yosemite-text-list.html)
• Photographic virtual tour of Yosemite National Park (http://www.UntraveledRoad.com/USA/Parks/Yosemite.htm)
• 3D Panoramas of Yosemite National Park – Don Bain's Virtual Guidebook (http://virtualguidebooks.com/CentralCalif/Yosemite.html)
• Interactive trail map (http://www.carto.net/williams/yosemite/)
• Yosemite National Park (http://www.nationalparksgallery.com/parks/Yosemite-National-Park) - National Parks Gallery

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