The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes (not unlike Japan) that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed. Close-up of granite from Yosemite National Park, valley of the Merced River Quarrying granite for the Mormon Temple, Utah Territory. ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... The Precambrian (Pre-Cambrian) is an informal name for the eons of the geologic timescale that came before the current Phanerozoic eon. ... Yosemite National Park (pronounced Yo-SEM-it-ee, IPA: ) is a national park located largely in Mariposa and Tuolumne Counties, California, United States. ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... This article or section cites very few or no references or sources. ... The Juan de Fuca plate sinks below the North America plate at the Cascadia subduction zone. ... The Paleozoic Era (from the Greek palaio, old and zoion, animals, meaning ancient life) is the earliest of three geologic eras of the Phanerozoic eon. ... For other uses, see Rock (disambiguation). ... An island arc is a type of archipelago formed by plate tectonics as one oceanic tectonic plate subducts under another and produces magma. ... For other uses, see Volcano (disambiguation). ... Volcanic rock on North America Plutonic rock on North America Igneous rocks form when rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i. ...

Most of the rock now exposed in the park is granitic, having been formed 210 to 80 million years ago as igneous diapirs 6 miles (10 km) below the surface. Over time, most of the overlying rock was uplifted along with the rest of the Sierra Nevadas and was removed from the area by erosion. This exposed the granitic rock to much lower pressure, and it was also subjected to erosion in the forms of exfoliation and mass wasting. A lava lamp illustrates the basic principle of diapirism. ... This article is about the mountain range in the Western United States. ... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as an operation of Mathematical morphology, see Erosion (morphology) Erosion is displacement of solids (soil, mud, rock and other particles) by the agents of ocean currents, wind, water, or ice by downward or down-slope movement... Geological exfoliation of granite at Enchanted Rock State Natural Area, Texas, USA Exfoliation in geology is a weathering process, mainly caused by freeze-thaw cycles. ... Mass wasting, also known as mass movement or slope movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. ...

Starting about 3 million years ago a series of glaciations further modified the area by accelerating the erosion. During that time large glaciers periodically filled the valleys and canyons. Landslides and river erosion have been the primary erosive forces since the end of the last ice age, which ended in this area around 8000 BC. A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ... Glacial and Glaciation redirect here. ... Fljótsdalur in East Iceland, a rather flat valley In geology, a valley is a depression with predominant extent in one direction. ... Grand Canyon, Arizona Noravank Monastery complex and canyon in Armenia. ... Landslide of soil and regolith in Pakistan A landslide is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. ... For other uses, see River (disambiguation). ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...

Generalized geologic map of the Yosemite area. (USGS image)

Image File history File links Download high-resolution version (734x666, 724 KB)PD USGS image from http://geology. ... Image File history File links Download high-resolution version (734x666, 724 KB)PD USGS image from http://geology. ...

Formation of exposed rocks

Passive to active margin

The area of the park was astride a passive continental margin (similar to the east coast of present-day United States) during the Precambrian and early Paleozoic. Sediment was derived from continental sources and was deposited in shallow water. The limestones, sandstones, and shales thus created have since been metamorphosed into marble, quartzite, and slate. These rocks are now exposed on isolated pendants in the northern and central parts of the park (Snow Lake Pendant in the Emigrant Wilderness is a good example).  Sediment  Rock  Mantle The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs. ... This article does not cite any references or sources. ... Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth due to erosion by flash flooding over millions of years Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. ... Shale Shale is a fine-grained sedimentary rock whose original constituents were clays or muds. ... Venus de Milo, front. ... Quartzite Quartzite (from German Quarzit[1]) is a hard, metamorphic rock which was originally sandstone. ... Slate Slate Macro Slate roof Slate is a fine-grained, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. ... A stand of Mountain Hemlock in the Emigrant Wilderness The Emigrant Wilderness is a 113,000 acre (45,700 ha) wilderness area in the Sierra Nevada of California, USA. It is bordered by Yosemite National Park on the south, the Toiyabe National Forest on the east, and California State Highway...

Starting in the mid-Paleozoic and lasting into the early Mesozoic, a Convergent Plate Boundary transported many of the above-mentioned seabed sediments into the area of the park (possibly during the Antler orogeny). Heat generated from the subduction led to the creation of an island arc of volcanoes on the west coast of Laurentia (proto-North America) between the late Devonian and Permian periods. These rocks were incorporated into proto-North America by the middle of the Triassic, some of them finding their way to the area of the park. Most of these igneous and sedimentary rocks have since been heavily metamorphosed, uplifted and eroded away. Outcrops of the resulting Shoo Fly Complex (made of schists and gneisses) and younger Calaveras Complex (a mélange of shale, siltstone, and chert with mafic inclusions) are now found in the western side of the park. The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... The Antler orogeny is an orogeny that extensively deformed Paleozoic rocks of the Great Basin in Nevada during Late Devonian and Early Mississipian time. ... The Juan de Fuca plate sinks below the North America plate at the Cascadia subduction zone. ... An island arc is a type of archipelago formed by plate tectonics as one oceanic tectonic plate subducts under another and produces magma. ... This article or section does not adequately cite its references or sources. ... Artists illustration of a Devonian scene. ... The Permian is a geologic period that extends from about 299. ... The Triassic is a geologic period that extends from about 251 ± 0. ... Look up preston in Wiktionary, the free dictionary. ... Schist The schists form a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. ... Gneiss Gneiss (IPA: ) is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ... In geologic context, mélange is a large scale breccia formed in the accretionary wedge above a subduction zone. ... Siltstone Siltstone is a geological term for a sedimentary rock whose composition is intermediate in grain size between the coarser sandstone and the finer mudstone. ... Chert Chert (IPA: ) is a fine-grained silica-rich cryptocrystalline sedimentary rock that may contain small fossils. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ...

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. Most of the remaining rocks are exposed as 'roof pendents' in the eastern metamorphic zone. Mount Dana and Mount Gibbs are made of these metavolcanic rocks. Only 5% of the rocks exposed in Yosemite National Park are metamorphic. (Geology of U.S. Parklands, page 218) The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ... Glacier-sliced Half Dome, Yosemite, a classic granite dome of the Sierra Nevada Batholith The Sierra Nevada Batholith is a large batholith in the Sierra Nevada mountain range, USA, and is a continuous granitic formation that forms much of the Sierra Nevada mountain range of California. ... Mount Dana is a mountain on the eastern edge of Yosemite National Park and is the second highest peak within the park after Mount Lyell. ... Mount Gibbs is a mountain in the Sierra Nevada, located 3 km south of Mount Dana. ...

Pluton emplacement

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 BP. Also starting 150 million years ago was an increase in the westward drift rate of the North American Plate. The resulting orogeny (mountain-building event) is called the Nevadan orogeny by geologists. The resulting Nevadan mountain range (also called the Ancestral Sierra Nevada) was 15,000 feet (4500 m) high and was made of sections of seafloor and mélange. Pluton redirects here. ...  The North American plate, shown in brown The North American Plate is a tectonic plate covering most of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... // Orogeny (Greek for mountain generating) is the process of mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within... For other uses, see Mountain (disambiguation). ... The Nevadan Orogeny was a major mountain building event that took place along the western edge of ancient North America between the Mid to Late Jurassic(between about 180 and 146 million years ago). ... In geologic context, mélange is a large scale breccia formed in the accretionary wedge above a subduction zone. ...

These rocks were later metamorphosed and today can be seen in the gold-bearing metamorphic belt of California's Mother Lode country. In the area of the park these rocks are exposed along the Merced River and California State Route 140. 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. GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ... Official language(s) English Capital Sacramento Largest city Los Angeles Largest metro area Greater Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ... Mother Lode is a term associated with the mining of gold. ... The Merced River is in California. ... California State Route 140 is an east-west, two-lane highway in central US state California, 102 miles (164 km) in length. ...

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. All told there have been more than 50 plutons found in the park. A few miles (several km) of material was eroded away, leaving the Nevadan mountains as a long series of hills a few hundred feet (tens of meters) high by 25 million years ago. // The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... The Sevier orogeny was a mountain-building event that affected western North America between aproximately 140 million years ago (Ma), and 50 Ma. ...

Cenozoic activity

Volcanism

Starting 20 million years ago and lasting until 5 million years ago a now-extinct extension of Cascade Range volcanos erupted, bringing large amounts of igneous material in the area. These igneous deposits blanketed the region north of the Yosemite area. Some lava associated with this activity poured into the Grand Canyon of the Tuolumne and formed Little Devils Postpile (a smaller but much older version of the columnar basalt palisades in nearby Devils Postpile National Monument). “Cascades” redirects here. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Basalt Basalt is an extrusive igneous rock, sometimes porphyritic, and is often both fine-grained and dense. ... The longer fragments of basalt at the base of the cliff can be larger than a person. ...

In the late Cenozoic, extensive volcanism occurred east of the park area. Within the Yosemite region, andesitic lava flows and lahars flowed north of the Grand Canyon of the Tuolumne and volcanic dikes and plugs developed from faults on the flanks of Mount Dana. There is also evidence for a great deal of rhyolitic ash covering the northern part of the Yosemite region 30 million years ago. This and later ash deposits have been almost completely eroded away (especially during the ice ages). The Cenozoic Era (IPA pronunciation: ); sometimes Caenozoic Era or Cainozoic Era (in the United Kingdom), meaning new life (Greek (kainos), new, and (zoe), life), is the most recent of the three classic geological eras. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Lahar from a March 1982 eruption of Mount St. ... The Grand Canyon of the Tuolumne, looking west. ... A dike in geology refers to a tabular intrusive igneous body. ... Geologic faults, fault lines or simply faults are planar rock fractures, which show evidence of relative movement. ... Rhyolite This page is about a volcanic rock. ...

Volcanic activity persisted past 5 million years BP east of the current park borders in the Mono Lake and Long Valley areas. The most significant activity was the creation of the Long Valley Caldera about 700,000 years ago in which 25,000 times as much material was erupted than in the 1980 eruption of Mt. Saint Helens. The most recent activity was the eruption of the Mono-Inyo Craters from 40,000 to 600 years ago. Mono Lake is an alkaline and hypersaline lake in California, United States that is a critical nesting habitat for several bird species and is one of the most productive ecosystems in North America[citation needed]. // Satellite photo of Mono Lake Mono Craters to the right of the image are rhyolitic... Long Valley Caldera is a depression in eastern California that is adjacent to Mammoth Mountain. ... Long Valley Caldera is a depression in eastern California that is adjacent to Mammoth Mountain. ... The 1980 eruption of Mount St. ... One of the Mono craters: an excellent example of a rhyolite dome. ...

Uplift and erosion

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. Tributary streams ran more-or-less in line with the Sierras, therefore not having their gradients increased. Thus their rate of valley cutting was not significantly affected. The results were hanging valleys and cascading waterfalls where the tributaries met the main streams. 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. However, Yosemite valley was not created by streams or fault lines (to create a graben valley), such was suggested by geologist Josiah Whitney. Glaciers shaped the Yosemite Valley, and can easily be confused with a graben valley. (Example of a graben valley is Death Valley is California) For other uses, see Gradient (disambiguation). ... Bridal Veil Falls in Yosemite National Park flowing from a hanging valley. ... This article does not adequately cite its references or sources. ... Owens Valley is the arid ranching valley of the Owens River in southeastern California in the United States. ... Basin and Range index map - USGS The Basin and Range Province is a particular type of topography that covers much of the southwestern United States and northwestern Mexico that is typified by elongate north-south trending arid valleys bounded by mountain ranges which also bound adjacent valleys. ... The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ... Austrias longest glacier, the Pasterze, winds its 8 km (5 mile) route at the foot of Austrias highest mountain, the Grossglockner A glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. ... Death Valley is a valley in the U.S. states of California and Nevada, and is the location of the lowest elevation in North America at 282 ft (86 m) below sea level. ...

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 granite 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. A granite dome is a dome of granite, formed by exfoliation. ... Scree or detritic cone is a term given to broken rock that appears at the bottom of crags, mountain cliffs or valley shoulders. ... Glacial till with tufts of grass Till is an unsorted glacial sediment. ...

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. The great majority of Yosemite Valley's widening, for example, was due to joint-controlled rockfall. In fact, only 10% of its widening and 12% of its excavation are thought to be the result of glaciation (Yosemite: A Visitors Companion, pgs 75-76). Large, relatively unjointed volumes of granite form domes such as Half Dome and monoliths like the 3604 feet (1098 m) high El Capitan. Closely-spaced joints lead to the creation of columns, pillers, and pinnacles such as Washington Column, Cathedral Spires, and Split Pinnacle. A monolith is a geological or technological feature such as a mountain, consisting of a single massive stone or rock. ... El Capitan is a 3,000-foot (1000m) vertical rock formation in Yosemite National Park, located on the north side of Yosemite Valley, near its western end. ...

Glaciations

Starting about 2 to 3 million years ago a series of glaciations further modified the area by accelerating mass wasting through ice-wedging, glacial plucking, scouring/abrasion and the release of pressure after the retreat of each glaciation. Severe glaciations formed very large glaciers that tended to strip and transport top soil and talus piles far down glacial valleys, while less-severe glaciations deposited a great deal of glacial till further up in the valleys. Mass wasting, also known as mass movement or slope movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. ... Plucking, in the sense relating to glaciers, is when a glacier erodes away chunks of bedrock to be later deposited as glacial erratics. ... Topsoil is the uppermost layer of soil, usually the top six to eight inches. ... Talus (which is Latin for ankle-bone) may refer to: The talus bone, a bone connecting the leg to the foot Talos, a rock-throwing giant made of bronze in Greek mythology A sloping mass of loose rocks at the base of a cliff Scree, small broken rock found on... Categories: Geology stubs | Glaciology | Sedimentary rocks ...

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. The Sherwin may have lasted almost 300 thousand years and ended about 1 million years ago. A Sherwin-age glacier was almost surely responsible for the major excavation and shaping of Yosemite Valley and other canyons in the area.

The Tahoe, Tenaya, and Tioga stages were part of the Wisconsinan glaciation. The Tahoe glacial stage is thought to have reached its maximum extent around 70,000 to 130,000 years ago; little is known about the more recent Tenaya. Evidence also suggests that the most recent local glacial stage, the Tioga, started about 28,000 cal (calibrated [1]) years ago, reached its maximum extent 20,000 to 25,000 cal yr ago, and ended by ~15,000 cal yr ago. Glaciers reformed in the highest cirques during a minor late-glacial readvance, the Recess Peak event,, between about 14,200 and 13,100 yr ago. This article or section should be merged with Wisconsin glaciation The Wisconsinian was the last major advance of continental glaciers in North America. ...

After that, glaciers appear to have been absent from the range until about 3200 cal yr ago, when small glaciers reappeared in the highest cirques. This readvance records the onset of Neoglaciation in the Sierra Nevada. Neoglaciation in the range culminated during the "Little Ice Age," a term originally coined by Francois Matthes in the Sierra Nevada, but now widely accepted as referring to a period of global glacial expansion between about AD 1250 to 1900. Moraines in the Sierra Nevada related to the Little Ice Age event are termed Matthes deposits. They are common in north-facing cirques and below modern glaciers in the High Sierra and are typically fresh, unstable, and often ice-cored. Good examples of Matthes moraines can be found below the Palisade Glacier (the largest glacier in the range), Lyell and Maclure glaciers in southern Yosemite N.P., and the smaller glaciers below Mount Dana, Kuna Peak, Mount Conness, and Matterhorn Peak. Mount Dana is a mountain on the eastern edge of Yosemite National Park and is the second highest peak within the park after Mount Lyell. ... Matterhorn Peak is a mountain in the U.S. state of California. ...

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 Russell (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). The Tuolumne River is one of the major rivers draining the western slope Sierra Nevada mountains of California. ... Hetch Hetchy Valley is a glacial valley in Yosemite National Park in California. ... Richard B. Russell Lake is a man-made lake created by the construction of Richard B. Russell Dam on the Savannah River bordering Georgia and South Carolina. ... Mono Lake is an alkaline and hypersaline lake in California, United States that is a critical nesting habitat for several bird species and is one of the most productive ecosystems in North America[citation needed]. // Satellite photo of Mono Lake Mono Craters to the right of the image are rhyolitic... Mount Dana is a mountain on the eastern edge of Yosemite National Park and is the second highest peak within the park after Mount Lyell. ... Mount Conness is a mountain in the Sierra Nevada mountain range, to the west of the Hall Natural Area. ... Moraine at Mono Lake, California, United States Moraines clearly seen on a side glacier of the Gorner Glacier, Zermatt, Switzerland. ...

Some domes in the park were covered by glaciers and modified into roche moutonnées, which are characterized by having a smooth, rounded side and a steep face. The rounded side was where the glacier flowed over the dome and the steep side is where the glacier flowed away from it. The steepness is caused by glacial plucking of rock along fracture joints. Good examples in the park are Liberty Cap, Lembert Dome, and Mount Broderick. Half Dome was created by a different process, but erosion acting on jointing planes was still the major factor. In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. ... Liberty Cap is a granite dome in Yosemite National Park, California, USA. It lies next to Nevada Fall, on the John Muir Trail. ... Lembert Dome is a granite dome in Yosemite National Park, California, USA. Lembert Dome soars 800 feet (240 m) above Tuolumne Meadows and the Tuolumne River and can be hiked starting at the Tioga Road in the heart of Tuolumne Meadows, 8 miles west of the Tioga Pass Entrance to... Half Dome is a granite dome in Yosemite National Park, located at the eastern end of Yosemite Valley — possibly Yosemites most familiar sight. ...

Controversy

The origin of the geological landscapes of the park have been under debate since 1865. At that time, Josiah Whitney, then chief geologist of California, proposed that Yosemite Valley is a graben: a downdropped block of land surrounded by faults. John Muir proposed that Yosemite Valley and Hetch Hetchy Valley were formed purely by glacial action. In 1930, Francois Matthes proposed a hybrid hypothesis, where most of the depth of the valley was gouged by water erosion, the rest by glacial action. The glacial action also claimed to have widened the valley. 1865 (MDCCCLXV) is a common year starting on Sunday. ... Portrait of Josiah Whitney by Silas Selleck, 1863 Josiah Dwight Whitney (November 23, 1819-August 15, 1896) was a professor of geology at Harvard University (from 1865), and was chief of the California Geological Survey (1860-1874). ... Official language(s) English Capital Sacramento Largest city Los Angeles Largest metro area Greater Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ... Yosemite Valley with Half Dome in the distance. ... USGS image A graben is a depressed block of land bordered by parallel faults. ... For other persons named John Muir, see John Muir (disambiguation). ... Hetch Hetchy Valley is a glacial valley in Yosemite National Park in California. ... Year 1930 (MCMXXX) was a common year starting on Wednesday (link will display 1930 calendar) of the Gregorian calendar. ...

More recently, the debate has been reopened by Jeffrey Schaffer, who suggests that the role of glaciers and other erosion processes has been dramatically overstated. Schaffer states that Yosemite Valley above 5600 feet (1700 m), for example, has changed relatively little in the past 30 million years. Other than being slightly larger, if one could look back in time and see them, the major features would be recognizable to the modern eye. Schaffer believes that the numerous joint planes have had the greatest impact on the geomorphology of the Park's major features. This is in contradiction to the consensus view that huge highly-abrasive glaciers acting on joint planes combined with a great deal of uplift over just the past couple million years was the primary shaping force of the features (such rapid uplift would have greatly accelerated all types of erosion). Surface of the Earth Geomorphology is the study of landforms, including their origin and evolution, and the processes that shape them. ...

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
• Yosemite National Park: A Natural History Guide to Yosemite and Its Trails, Jeffrey P. Schaffer, (Wilderness Press, Berkeley; 1999) ISBN 0-89997-244-6
• Geology of U.S. Parklands: Fifth Edition, Eugene P. Kiver and David V. Harris (Jonh Wiley & Sons; New York; 1999) ISBN 0-471-33218-6

See also: List of guidebooks about the Sierra Nevada The following is a partial list of guidebooks about the Sierra Nevada of California, USA. Please see Sierra Nevada for more information. ...

External links

• Origin of Yosemite Valley, Chapter 4, Glaciers of California, by Bill Guyton

• Geology of the National Parks: Yosemite National Park's Geology (USGS online exhibit)
• The Geologic Story of Yosemite National Park by Dr. N. King Huber (USGS, 1987) USGS Bulletin 1595. Complete text online