Yosemite National Park | Yosemite Weather | Yosemite Lodging
About Yosemite National Park:
Yosemite is one of the largest and least fragmented habitat blocks in the Sierra Nevada, and the park supports a diversity of plants and animals. The park has an elevation range from 2,127 to 13,114 feet (648 to 3,997 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 documentation 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 (1,200 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.
Fast Fact of Yosemite National Park:
where is Yosemite National Park:Central California's Sierra Nevada mountain range
Yosemite National Park Location:Tuolumne, Mariposa, & Madera counties, California, USA
Nearest City of Yosemite National Park:Mariposa, California
Yosemite National Park Coordinates:37°44′43″N 119°35′54″W
Yosemite National Park Area:761,268 acres (308,074 ha)
Geography of the Yosemite Area:
The 1,189 sq mi (3,080 km2) park is roughly the size of the U.S. state of Rhode Island and contains thousands of lakes and ponds, 1,600 miles (2,600 km) of streams, 800 miles (1,300 km) of hiking trails, and 350 miles (560 km) of roads. 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.
Yosemite Weather Forecast:
Rocks and Erosion:
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 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. The single most erosive force over the last few million years has been 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.
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, standing at 13,120 ft. The Lyell Glacier is the largest glacier in Yosemite National Park and is one of the few remaining in the Sierra Nevada today.
The park has three groves of ancient Giant Sequoia (Sequoiadendron giganteum) trees; the Mariposa Grove (200 trees), the Tuolumne Grove (25 trees), and the Merced Grove (20 trees). This species grows larger in volume than any other and is one of the tallest and longest-lived.
Water and Ice:
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 m²), two reservoirs, and 1,700 miles (2,700 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 (910 to 3,400 m) in the park, are generally wetlands, as are the riparian habitats found on the banks of Yosemite's numerous streams and rivers.
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 Yosemite (the Palisades Glaciers are the largest in the Sierra Nevada) and covers 160 acres (65 ha). 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). Climate change 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.
Climate of Yosemite National Park:
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 / 1,560 metres), mean daily temperature ranges from 36 to 67 °F (2 to 19 °C). At the lower elevations below 5,000 feet (1,500 m), temperatures are hotter; the mean daily high temperature at Yosemite Valley (elevation 3,966 feet / 1,209 metres) varies from 46 to 90 °F (8 to 32 °C). At elevations above 8,000 feet (2,400 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 Valley is the main attraction in the park for the majority of visitors, and a bustling hub of activity during "tourist season", with an array of visitor facilities clustered in the middle. There are both hiking trail loops that stay within the valley and trailheads that lead to higher elevations, all of which afford glimpses of the park's many scenic wonders.
Yosemite Valley represents only one percent of the park area, but this is where most visitors arrive and stay. More than half a dozen creeks tumble from hanging valleys at the top of granite cliffs that can rise 3000–4000 feet (900–1200 m) above the valley floor, which itself is 4000 ft (1200 m) above sea level. These streams combine into the Merced River, which flows out from the western end of the valley, down the rest of its canyon to the San Joaquin Valley. The flat floor of Yosemite Valley holds both forest and large open meadows, which provide breathtaking views of the surrounding crests and waterfalls.
Below is a description of these features, looking first at the walls above, moving west to east as a visitor does when entering the valley, then visiting the waterfalls and other water features, returning east to west with the flow of water.
The first view of Yosemite Valley many visitors see is the Tunnel View. So many paintings were made from a viewpoint nearby that the National Park Service named that viewpoint Artist Point.
The view from the lower (western) end of the Valley contains the great granite monolith El Capitan on the left, and Cathedral Rocks on the right with Bridalveil Fall. Just past this spot the Valley suddenly widens with the Cathedral Spires, then the pointed obelisk of Sentinel Rock to the south. Across the Valley on the northern side are the Three Brothers, rising one above the other like gables built on the same angle – the highest crest is Eagle Peak, with the two below known as the Middle and Lower Brothers.
To this point, the Valley has been curving gently to the left, to the north. Now a grand curve back to the right begins, with Yosemite Falls on the north, followed by the Royal Arches, topped by North Dome. Opposite to the south is Glacier Point, 3,200 feet (975 m) above the Valley floor. At this point the Valley splits into two, one section slanting northeast, with the other curving from south to southeast. Between them both, at the eastern end of the valley, is Half Dome, the most famous and most recognizable natural feature in the Sierra Nevada. Above and to the northeast of Half Dome is Cloud's Rest; at 9926 feet (3025 m), the highest point around Yosemite Valley.
A fan of creeks and forks of the Merced River take drainage from the Sierra crest and combine at Merced Lake. The Merced then flows down to the end of its canyon (Little Yosemite Valley), where it begins what is often called the Giant Staircase. The first drop is Nevada Fall, which drops 594 feet (181 m), bouncing off the granite slope below it. Below is Vernal Fall, 317 feet (97 m) high, one of the most picturesque waterfalls in the Valley. The Merced then descends rapids to meet Illilouette Creek, which drops from the valley rim to form Illilouette Fall. They combine at the base of the gorges that contain each stream, and then flow around the Happy Isles to meet Tenaya Creek at the eastern end of Yosemite Valley proper.
Tenaya Creek flows southwest from Tenaya Lake and down Tenaya Canyon, finally flowing between Half Dome and North Dome before joining the Merced River. The following falls tumble from the Valley rim to join it at various points:
- Yosemite Falls (2,425 ft) Upper Yosemite Fall (1,430 ft), the middle cascades (675 ft), and Lower Yosemite Fall (320 ft). (Yosemite Creek)
- Snow Creek Falls (2,140 ft)
- Sentinel Falls (1,920 ft)
- Ribbon Fall (1,612 ft)
- Royal Arch Cascade (1,250 ft)
- Lehamite Falls (1,180 ft)
- Staircase Falls (1,020 ft)
- Bridalveil Fall (620 ft). (Bridalveil Creek)
- Nevada Fall (594 ft)
- Silver Strand Falls (574 ft)
- Vernal Fall (318 ft)
Natural Yosemite Valley:
Geology of the Yosemite area:
The oldest of these granitic rocks occur along the Merced River Gorge west of the valley and are thought to be 114 million years old. The El Capitan pluton intruded the valley forming most of the granitic rock that makes up much of the central part of the valley including Cathedral Rocks, Three Brothers and of course El Capitan. The youngest pluton of Yosemite Valley is the 87 million year old Half Dome granodiorite which makes up most of the rock seen at Glacier Point, the Royal Arches and its namesake Half Dome.
After the retreat of many of these glaciers, a stand of Lake Yosemite developed. The valley floor owes its flatness to sediment deposited by these stands (the last glaciers in the valley were small and did not remove much old lake sediment). The last stand of Lake Yosemite was about 5.5 miles (8.9 km) long and was impounded by a terminal moraine near the base of El Capitan. It was later filled by sediment, becoming a swampy meadow.
The parallel Tenaya Canyon and Little Yosemite Canyon glaciers were, at their largest, 2,000 feet (600 m) deep where they flowed into the Yosemite Valley near the base of Half Dome. They also formed Cloud's Rest behind Half Dome as an arête.
Near Glacier Point there is 2,000 feet (600 m) of mostly glacial sediment with at least six separate sequences of Lake Yosemite sediments. Here, huge and highly erosive pre-Wisconsinian glaciers are thought to be responsible for excavating the bedrock valley floor, and much smaller Wisconsinian glaciers were responsible for depositing glacial debris.
Ecology of Yosemite Valley:
Trees – Ponderosa Pine, Lodgepole Pine, Sugar Pine, White Fir, Incense-cedar, California black oak, Interior live oak, Coast Douglas-fir, California laurel, Bigleaf Maple, Scouler's Willow, Pacific Dogwood, White alder, Western Balsam Poplar
Shrubs – Whiteleaf manzanita, Mountain misery, Western azalea, American dogwood, Buckbrush, Deer brush, Sierra gooseberry
Wildflowers – Indian pink, Soap plant, California Poppy, Miner's lettuce, Purple Chinese Houses, Purple milkweed, Pacific Starflower, Western buttercup, Pineapple weed
Birds – Dark-eyed Junco, Mountain Chickadee, Black-headed Grosbeak, White-headed Woodpecker, Steller's Jay, American Dipper, Common Raven
Reptiles – Gilbert's Skink, Northern Alligator Lizard, Rattlesnake
Amphibians – Sierra Nevada Salamander
- The John Muir Trail --- running 212 miles (341 km) to Mount Whitney
- The Mist Trail --- with views of Vernal Falls and Nevada Fall
- The Four Mile Trail --- leading to Glacier Point.
- The Yosemite Falls Trail --- to the top of Yosemite Falls
Ecology of the Sierra Nevada:
Along much of Yosemite's western boundary, habitats are dominated by mixed coniferous forests of Ponderosa Pine, Sugar Pine, Incense-cedar, White Fir, 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, because of 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, Cougar, 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, because of their higher elevation and lower complexity. Species likely to be found include Golden-mantled Ground Squirrel, Chickaree, Fisher, Steller's Jay, Hermit Thrush, and Northern Goshawk. Reptiles are not common, but include Rubber Boa, western fence lizard, and Northern Alligator Lizard.
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 Grey Owl, Willow Flycatcher, Yosemite Toad, and Mountain Beaver.
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 are eventually 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.
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 is expected to help the germination issue.
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 (Centaurea solstitialis), Sweet Clover (Melilot spp.), Himalayan Blackberry (Rubus armeniacus), Cut-leaved Blackberry (Rubus laciniatus) and Large Periwinkle (Vinca major).
Activities at Yosemite Valley:
Most park visitors stay just for the day, and only visit locations within Yosemite Valley that are easily accessible by automobile. There is a US$20 per automobile user fee to enter the park. 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 Valley 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. Camp 4 was added to the National Register of Historic Places in 2003.
Over 800 miles (1,300 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 can be 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. Park rangers encourage visitors to experience portions of the park in addition to Yosemite Valley.
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.
As an alternative to driving, bicycles are allowed on the roads. However, bicycles are only allowed off-road on 12 miles (19 km) of paved trails in Yosemite Valley itself; mountain biking is not allowed.
List of Yosemite destinations:
A list of Yosemite destinations includes hiking trails and things to see:
Near the Yosemite Valley:
- Yosemite Falls
- Bridalveil Falls
- Mirror Lake
- Mist Trail
- Half Dome
Near Glacier Point:
- Panorama Trail from Glacier Point
- McGurk Meadow
- Ostrander Lake
- Mono Meadow
- Taft Point
- Sentinel Dome
- Chilnualna Falls
- Alder Creek
- Mariposa Grove
- Wapama Falls
- Rancheria Falls
- Soda Springs
- Dog Lake
- Lembert Dome
- Glen Aulin
- Elizabeth Lake
- Cathedral Lakes
- John Muir Trail
- Mono Pass
- Gaylor Lakes
Things to see at in Yosemite Park:
Popular things to look at in Yosemite Park include:
The following is a list of Yosemite waterfalls, including ephemeral falls:
- Bridalveil Fall 620 feet (190 m)
- Chilnualna Falls 690 feet (210 m)
- Horsetail Fall 2,100 feet (640 m)
- Illilouette Fall 370 feet (110 m)
- Lehamite Falls 1,180 feet (360 m)
- Nevada Fall 594 feet (181 m)
- Pywiack Cascade 600 feet (180 m)
- Quaking Aspen Falls 25 feet (7.6 m)
- Ribbon Fall 1,612 feet (491 m)
- Royal Arch Cascade 1,250 feet (380 m)
- Sentinel Fall 1,920 feet (590 m)
- Silver Strand Falls 574 feet (175 m)
- Snow Creek Falls 2,140 feet (650 m)
- Staircase Falls 1,020 feet (310 m)
- Three Chute Falls 80 feet (24 m)
- Tueeulala Falls 840 feet (260 m)
- Vernal Fall 317 feet (97 m)
- Wapama Falls 1,700 feet (520 m)
- Waterwheel Falls 300 feet (91 m)
- Wildcat Falls 630 feet (190 m)
- Yosemite Falls 2,425 feet (739 m)
- Half Dome
- El Capitan
- Cathedral Rocks
- The Three Brothers
- Sentinel Rock
- Yosemite Point
- Glacier Point
For information about the tree, see Sequoiadendron. Groves of the trees include:
- Mariposa Grove
- Tuolumne Grove
- Merced Grove
- Glacier Point
- Olmsted Point
- Tunnel View
- El Portal View
- O'Shaughnessy Dam
- Cascade View
- Pothole Dome
- Lembert Dome
- Yosemite Valley itself contains many views
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 (1.0 km) face of El Capitan. Classes are offered by numerous groups on rock climbing.
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 18th century in his Sketch Book. Between 1929 and 1973, the show was organized by Ansel Adams.
Bicycle rentals are available in Yosemite Valley spring through fall. Over 12 miles (19 km) 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.
Water activities are plentiful during warmer months. Rafting can be done through the Yosemite Valley on the Merced River. There is also a swimming pool available at Curry Village
In 2010, Yosemite National Park was honored with its own quarter under the America the Beautiful Quarters program.
The total 2,425 feet (739 m) from the top of the upper falls to the base of the lower falls qualifies Yosemite Falls as the sixth highest waterfall in the world, though with the recent discovery of Gocta Cataracts, it appears on some lists as seventh.
Although often referred to as a "two-stage drop", the falls actually consist of three sections:
Upper Falls: The 1,430-foot (440 m) plunge alone is among the twenty highest waterfalls in the world. Trails from the valley floor and down from other park areas outside the valley lead to both the top and base of Upper Yosemite Falls. The upper fall is formed by the swift waters of Yosemite Creek, which, after meandering through Eagle Creek Meadow, hurl themselves over the edge of a hanging valley in a spectacular and deafening show of force.
Lower Falls: The final 320-foot (98 m) drop adjacent to an accessible viewing area, provides the most-used viewing point for the waterfalls. Yosemite Creek emerges from the base of the Lower Falls and flows into the Merced River nearby. Like many areas of Yosemite the plunge pool at the base of the Lower Falls is surrounded by dangerous jumbles of talus made even more treacherous by the high humidity and resulting slippery surfaces.
In years of little snow, the falls may actually cease flowing altogether in late summer or fall. A very small number of rock climbers have taken the opportunity to climb the normally inaccessible rock face beneath the falls, although this is an extraordinarily dangerous undertaking; a single afternoon thunderstorm could restart the falls, sweeping the climbers off the face.
The Ahwahneechee Legend:
The Ahwahneechee people of Yosemite Valley called the waterfall "Cholock" and believed that the plunge pool at its base was inhabited by the spirits of several witches, called the Poloti. An Ahwaneechee folktale describes a woman going to fetch a pail of water from the pool, and drawing it out full of snakes. Later that night, after the woman had trespassed into their territory, the spirits caused the woman's house to be sucked into the pool by a powerful wind, taking the woman and her newborn baby with her.
Ecology of the Sierra Nevada:
The western and eastern Sierra Nevada have substantially different species of plants and animals, because the east lies in the rain shadow of the crest. The plants and animals in the east are thus adapted to much drier conditions.
The altitudes listed for the biotic zones are for the central Sierra Nevada. The climate across the north-south axis of the range varies somewhat: the boundary elevations of the biotic zones move by as much as 1,000 feet (300 m) from the north end to the south end of the range.
Western biotic zones:
Foothill Woodland and Chaparral Zone:
Sierra Nevada lower montane forest:
Upper Montane Forest:
Sierra Nevada Subalpine Forest:
The alpine zone begins near the 9,500 foot (2,900 m) elevation and is easily distinguished as it is above tree line. No trees grow in this zone due to the harsh climatic conditions. Short, cool summers with long, cold, and snowy winters are typical at these elevations. Many exposed granitic outcroppings, talus slopes, and boulder fields limit the amount of vegetation that grows here. The herbaceous plants need to flower and produce their seeds quickly during the short, frost-free period of summer. Some animal species that are adapted to this zone include the American Pika, Belding's Ground Squirrel, the Yellow-Bellied Marmot, and the endangered Sierra Nevada Bighorn Sheep. This zone can be viewed up close by hiking or climbing into the high elevations of the Sierra.
Eastern biotic zones:
The four highest eastern biotic zones are the same as the western zones, but at a higher elevation, due to less precipitation:
- Alpine zone: 12,000 feet (3700 m) and above
- Subalpine forest: 10,500 feet (3200 m) - 12,000 feet (3700 m)
- Upper montane forest: 9,000 feet (2700 m) - 10,500 feet (3200 m)
- Lower montane forest: 7,000 feet (2100 m) - 9,000 feet (2700 m) (heavily dominated by Jeffrey Pines).
In the Owens Valley, the Foothill Woodland Zone is replaced by a Pinyon-Juniper Woodland Zone, characterized by Single-leaf Pinyon Pines, Sierra Junipers. The underbrush contains Big Sagebrush (Artemisia tridentata) and blackbrush (Coleogyne ramosissima). Jeffrey Pines may occur along streams. Notable animals in this zone include the Pinyon Jay and the Desert Bighorn Sheep. The Pinyon-Juniper Woodland Zone extends down to 5,000 feet (1500 m) elevation.
Below 5,000 feet (1500 m), there is not enough precipitation to support trees. The zones below this elevation are the Sagebrush Scrub Zone, Saltbush Scrub Zone, and the Alkali Sink Zone. These zones are distinguished by soil salinity.
Exotic Plants in Yosemite National Park:
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 starthistle, sweet clovers (Melilotus spp.), Himalayan blackberry (Rubus discolor), Cut-leaved blackberry (Rubus laciniatus) and periwinkle (Vinca major).
Lodgepole Needle Miner:
The Lodgepole Needle Miner (Coleotechnites milleri) is an insect, endemic to the upper Tuolumne and Merced River watersheds of Yosemite National Park and one small headwaters drainage of the San Joaquin River (Sierra National Forest). It lives mostly within the needles of Lodgepole Pine for two years, emerging as a little gray moth for a few weeks in July of odd-numbered years. This keeps any predators from becoming effective control agents and allows populations to escalate rapidly. While regular prehistoric outbreaks of Lodgepole Needle Miners have been confirmed through dendrochronology, historic records document outbreaks from 1903 to 1921, 1933 to 1941, and 1947 to 1963.
Extensive stands of "Ghost Forest" and jackstrawed trees are still conspicuous throughout Sierra Nevada. Annual monitoring of Lodgepole Needle Miner density began in 1966, and 28 permanent plots are scattered north of the Cathedral Range. The current outbreak began in 1973 and has been sweeping around the south side of the Cathedral Range, arriving at Sunrise High Sierra Camp in 2001. The Ghost Forest which was evident at the crest between Tenaya Lake and Tuolumne Meadows in the late 1970s was noticeably reforested by 2000. Lodgepole Needle Miner defoliation currently extends over approximately 40,000 acres (162 km²), with nearly 10,000 acres (40 km²) of low to high mortality each year.
While lightning fires are frequent in lodgepole pine communities, they usually remain small, with estimated fire return intervals at Yosemite National Park that are long (relative to most other forest types). Thus, fire suppression activities are thought to have had little influence upon species composition, structure, fuels, and natural processes in lodgepole forests. Also, in comparison with Rocky Mountains lodgepole pine forests, fire plays a smaller role, and so the needle miner assumes greater importance in lodgepole pine forest population dynamics in the Sierra Nevada. However, Rocky Mountain lodepole forest dynamics are also heavily influenced by insect outbreaks, primarily bark beetles.
Plants that are Federal species of concern (former Category 2 species) under the Federal Endangered Species Act include:
- Three-bracted Onion (Allium tribracteatum),
- Yosemite Woolly Sunflower (Eriophyllum nubigenum),
- Congdon's Lomatium (Lomatium congdonii),
- Tiehm's Rock-cress (Arabis tiehmii),
- Slender-stemmed Monkeyflower (Mimulus filicaulis), and
- Bolander's Clover (Trifolium bolanderi).
Although Category 2 was abolished in 1996, species of concern is an informal term that refers to those species that might be declining or be in need of concentrated conservation actions to prevent decline. Therefore, these six species continue to be evaluated and managed by the National Park Service.
Four state-listed rare plant species are considered restricted and limited throughout all or a significant portion of their range, and may represent disjunct populations at the extreme end of their range:
- Yosemite Onion (Allium yosemitense),
- Tompkin's Sedge (Carex tompkinsii),
- Congdon's Woolly Sunflower (Eriophyllum congdonii), and
- Congdon's Lewisia (Lewisia congdonii).
Endangered or threatened species of animals that occur in the Sierra Nevada include:
- Sierra Nevada Bighorn Sheep
- California Condor
- Southwestern Willow Flycatcher
- Paiute Cutthroat Trout
- Lahontan Cutthroat Trout
- Owens Tui chub (Gila bicolor)
The Sierra contain three major types of wetland:
2. Lacustrine, and
Each of these types of wetlands varies in geographic distribution, duration of saturation, vegetation community, and overall ecosystem function. All three types of wetlands provide rich habitat for plant and animal species, delay and store seasonal floodwaters, minimize downstream erosion, and improve water quality.
Riverine wetlands are found within river and stream channels and are strongly influenced by seasonal runoff patterns. When inundated, riverine wetlands provide habitat for water-tolerant plants such as willows, and aquatic animals such as tadpoles and immature fish.
Lacustrine wetlands generally occur on river floodplains and along lakeshores and are influenced by seasonal variations in groundwater levels. These wetlands are rare in the mountain range, but support an abundance of warm-water loving plant and animal species.
Since the 1970s the United States has made substantial progress toward protecting and restoring wetland habitats. All federal land in the Sierra Nevada complies with a 1990 Presidential Executive Order that mandates 'no net loss' of wetlands, and requires federal agencies to map and protect all existing wetlands.
In 1996 the National Fish and Wildlife Service delineated and classified some of the wetlands of the Sierra Nevada, including all of Yosemite National Park. This was performed through an analysis of aerial photographs and topographic maps, as a part of the National Wetlands Inventory Web Site (NWI). The NWI maps have not been rigorously ground-truthed and only delineate wetlands larger than five acres (20,000 m²) in size.
The National Park Service restores to natural conditions wetlands that have been drained or filled in the past. Most recently in Yosemite Valley, the Cook's Meadow restoration project involved filling old drainage ditches that were draining the meadow and removing an old roadbed that was inhibiting water flow. These actions are currently being monitored with vegetation transects and mapping of surface water to determine how successful the project was in restoring the wetland.
Geology of the Yosemite Area:
Tectonic and volcanic activity:
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 (4,600 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 (9.7 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:
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. 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.