How The Yosemite Falls Were Formed. The Merced River forms the Vernal and Nevada Falls where great blocks of granite were first quarried and then carried away by the glaciers. These giant steps are located at the east end of the valley. After the ice age, the waterfalls now fell from Hanging valleys.
Lake Yosemite eventually filled in with silt, leaving today’s level valley floor. Gravity, commonly aided by water and ice, acting on slopes oversteepened by glacial undercutting, modifies the landscape most visibly.
When this happens, the water in Yosemite Falls thunders from the edge of the valley and more than 2,000 feet down, shaking the valley walls. But this "performance" lasts only as long as the snow that feeds Yosemite Creek does. By late summer the snows have all melted away and the once booming Yosemite Falls becomes a trickle.
Invasive Species: Invasive species have a negative impact on natural resources nationwide, including in Yosemite National Park. Non-native animal species, like the New Zealand mud snail, concern park scientists because this species can completely cover a river streambed, thereby altering the ecosystem.
The climate has made a change in temperature in Yosemite from global warming. It raised 3 degrees Celsius! The global climate change is impacting Yosemite. Scientists project that average temperatures in the park may rise by 6.7–10.3°F, or -14.05 - -12 degrees Celsius between 2000 and 2100.
Glaciers filled the V-shaped Yosemite Valley, widening, deepening and carving it into a "U" shape, forming hanging valleys from which waterfalls now cascade.
Since 2.6 million years ago there have been more than 40 cycles of glacial (cold) and interglacial (warm) periods. These glacial periods modified the landscape forming Yosemite Valley, other canyons, lakes, and many of the other features seen in Yosemite today.
The 1996 Yosemite Valley landslide occurred on July 10, 1996, near the Happy Isles trailhead in Yosemite Valley, Yosemite National Park, Mariposa County, California....1996 Yosemite Valley landslide.Aftermath of the landslideDateJuly 10, 1996Coordinates37.729°N 119.561°WCause162,000 tons of debris fell at speeds of up to 160 mphDeaths11 more row
Ice Age glaciers played an essential role in shaping Yosemite's landscape. Most of this ice had melted away due to natural warming by about 10,000 years ago. During a more recent cold period called the Little Ice Age, small glaciers formed below the highest peaks. Currently, two remain: the Lyell and Maclure glaciers.
The rocks which have fallen into the river assist the process of corrasion and this leads to further erosion. The river transports the rocks downstream and the channel becomes wider and deeper creating a V-shaped valley between interlocking spurs .
This map shows the extent of glacial cover in Yosemite National Park during the Tioga glaciation that was at its peak 18,000 years ago. Note the Grand Canyon of the Tuolumne (shown in photo above) and Yosemite Valley, which were formed initially by stream erosion, but then modified by glacial erosion.
30,000 years ago30,000 years ago. About 30,000 years ago, a smaller (but still relatively massive) ice sheet known as the Yosemite Glacier passed through the Valley.
Half Dome, like the other granite exposures in Yosemite, formed from so-called “intrusions” of magma—molten rock—that solidified underground to form massive granite bodies.
The different individual bodies of plutonic rocks in Yosemite were formed from repeated intrusions of magma into older host rocks beneath the surface of the Earth. These intrusions may have taken place over a time period as long as 130 million years.
Most rockfalls in Yosemite occur in the winter and early spring, during periods of intense rainfall, snow melt, and/or subfreezing temperatures, but many large rockfalls have also occurred during periods of warm, stable weather.
Most rockfalls in Yosemite are triggered by earthquakes, rainstorms, or rapid snow melt.
Thundering waterfalls are iconic signs of spring in Yosemite, usually reaching peak flow in late spring like 3,000-foot clockwork. They may also become one of the park’s most visible signs of change. Yosemite Falls, like many streams and waterfalls in the park, is fed almost entirely by snowmelt. Waterfall flow is largely determined by how much ...
Each month during the winter, rangers ski out to conduct snow surveys deep in the Yosemite wilderness. This data record stretches back to 1930 for some survey sites—among the longest continuous snow records in the western US.
Snowmelt is the lifeblood of Yosemite. Even after the springtime tumult of rushing rivers and roaring falls has passed, trickling meltwater continues to fill streambeds through the hot, dry summers of Yosemite’s Mediterranean climate.
Across California, 23 million people are served by the vast frozen reservoir of the Sierra Nevada snowpack.
At some elevations, this feedback loop alone accounts for more than 3.6°F of extra warming.
Snow from elsewhere in the Sierra Nevada supplies water to cities as distant as San Diego. Overall, 60% of California’s fresh water (and 75% of its agricultural water) comes directly from the Sierra Nevada snowpack.
Global climate change is impacting Yosemite. Worldwide emissions of greenhouse gases trap heat in the atmosphere, leading to rapid warming observed across the western US. Scientists project that average temperatures in the park may rise by 6.7–10.3°F between 2000 and 2100. This trend is already impacting glaciers, snowpack, waterfalls, ...
Restoration projects prevent unnatural growth-vegetation encroachment-in open areas to retain the historic views for which Yosemite is known. Yosemite scientists aim to restore the park's historic scenic vistas using sound cultural and ecological practices and processes.
Temperatures at the 4,000-foot Yosemite Valley can rise to more than 100°F in the summer with lows in the 20s and nearly 30 inches of snowfall, on average.
Fire managers use three tools to mimic fire's natural function in the ecosystem: prescribed fire, mechanical thinning, and wildland fire use. While visiting Yosemite, you may see evidence of any of these practices. Yosemite's social scientists use techniques to measure the quality of the visitor experience.
Soundscape. The acoustic environment of any area is made up of natural and human sounds. Cultural and historic sounds, like the rhythm of a horse-drawn wagon, are components, too. Sounds are an integral part of visitors' Yosemite experience.
In Yosemite, it is something that we manage carefully and continue to learn more about. Yosemite has an extensive fire history. Historically, fire was often seen as a negative force, but in recent years it has been realized that the benefits of fire in forests are numerous.
Many Yosemite visitors come to experience this worldwide vanishing resource. To study the topic, the National Park Service devised a system to measure sky brightness, and even remote parks like Yosemite face stray light pollution, particularly from the San Joaquin Valley.
What would you do if summer temperatures in your hometown were getting uncomfortably hot? Some of us might opt to spend more time inside—modifying our behavior to adjust to changes in the environment. Although most animals and plants don’t have access to air conditioning, other climate-linked changes in behavior and phenology have been observed in Yosemite.
Pika, a small, rabbit-like alpine mammal threatened by climate-related habitat loss in other areas, seems to be currently stable in Yosemite. Modern researchers observed them at all historic sites except Glen Aulin, where they concluded that they may have been present but undetected.
The geologic story of Yosemite National Park can be considered in two parts: (1) deposition and deformation of the metamorphic rocks and emplacement of the granitic rocks during the Paleozoic and Mesozoic; and (2) later uplift, erosion, and glaciation of the rocks during the Cenozoic to form today's landscape.
Instead, it is a composite of hundreds of smaller bodies of granitic rock that, as magma (molten material), intruded one another over a timespan of more than 100 million years. This multiplicity of intrusions is one of the reasons why there are so many varieties of granitic rock in Yosemite and the rest of the Sierra.
The plutonic rocks were generally formed during the Cretaceous period. Half Dome Granodiorite at Olmsted Point. The U.S. penny is used for scale. The different individual bodies of plutonic rocks in Yosemite were formed from repeated intrusions of magma into older host rocks beneath the surface of the Earth.
These plutonic rocks, formerly deep within the Earth, are now exposed at the surface, owing to deep erosion and removal of the formerly overlying rocks. Volcanic igneous rocks are erupted onto the Earth's surface and cool and solidify much more quickly than plutonic igneous rocks.
Iconic landmarks such as Yosemite Valley, Hetch Hetchy, Yosemite Falls, Vernal and Nevada Falls, Bridalveil Fall, Half Dome, the Clark Range, and the Cathedral Range are known throughout the world by the photographs of countless photographers, both amateur and professional.
Massive granite dominates the Yosemite area and much of the Sierra Nevada as well. Mount Hoffmann and most of the terrain visible from it are composed of granite, formed deep within the Earth by solidification of formerly molten rock material and subsequently exposed by erosion of the overlying rocks. Because of its massiveness and durability, ...
Landforms that are the result of glaciation include U-shaped canyons, jagged peaks, rounded domes, waterfalls, and moraines. Glacially-polished granite is further evidence of glaciation, and is common in Yosemite National Park.
Evolution of the Yosemite Valley The area that was to become the Sierra Nevada once lay beneath a sea at the west margin of North America. The rock that was formed on this sea floor from deposited silt. mud, and marine organisms was subsequently lifted above sea level and flexed into a mountain range surmounted by a chain ...
The deep excavation created by earlier glaciers, as much as 2,000 feet into bedrock beneath the present floor of Yosemite Valley, was already filled with glacial till and sediments long before the Tioga glaciation.
The last Valley glacier hat melted and its terminal moraine has dammed the Valley to create a shallow lake, Lake Yosemite. This was only the last of many Lake Yosemites that probably followed each glaciation. The deep excavation created by earlier glaciers, as much as 2,000 feet into bedrock beneath the present floor of Yosemite Valley, ...
The Ice Ages approach brought a colder climate and thinning forests. 1 million to 250,000 years ago . At least one and perhaps more glacial advances filled Yosemite Valley to its brim. Half Dome projected 900 feet above the ice, but many peaks to the north were engulfed.
Glaciers did not directly create today's free-leaping waterfalls, although they helped set the stage. The falls plunge into alcoves in the Valley walls, produced by frost-splitting of rock fragments off the lower parts of the cliffs over which the waterfalls formerly cascaded.
Ultimately a point is reached where the ice front can advance no farther because the ice melts there as rapidly as it is provided by inflow from upglacier.
In the winter of 1982, a rockfall dropped huge blocks of granite on Route 140 near the junction of the Old Coulterville Road, about 2 mi east of the Arch Rock Entrance Station ( fig. 49 ).
In contrast, El Capitan (right) is largely unjointed granite, and the pile of debris at its foot, though concealed in this photograph, is comparatively small. (Fig.
Unfractured granite is impermeable, and because weathering processes depend on the presence of moisture, exposed granite surfaces weather slowly . However, where buried by soil and in contact with a chemically reactive mixture of water, atmospheric gases, and organic decay products, granite weathers much more readily. Joints in the granite that provide avenues for deep circulation of ground water permit weathering to proceed well below the buried bedrock surface. As weathering penetrates the rock from joint surfaces, the edges and corners of the joint blocks are affected more rapidly than the sides, because they are attacked from two or three directions at once ( fig. 43 ). The unweathered remnant of granite in the center of the joint block becomes a rounded boulder, called a corestone, and the process of its formation is a form of exfoliation called spheroidal weathering ( fig. 44 ).
Thus, heavy winter snowfall or cool summer temperatures, or both, favor the growth of glaciers. If these conditions persist for a few centuries, possibly less, the layers of accumulating snow form a deposit thick enough for the snow in the lower part of the deposit to be compacted into ice ( fig. 52 ).
The record of glaciation in Yosemite National Park is very incomplete. Only for the last two major glaciations can the extent of the ice be reconstructed with any confidence. Older glacial deposits, if preserved at all, are so fragmentary that it is generally impossible to distinguish the separate ice advances that may have deposited them. The glaciers grew and melted away in response to climatic changes of long duration that were probably worldwide, and so a record of all the glaciations that might have affected Yosemite must be sought elsewhere.