Mammoth Mountain
Encyclopedia
Mammoth Mountain is a lava dome
complex west of the town of Mammoth Lakes, California
in the Inyo National Forest
of Madera County
and Mono County
. It is home to a large ski area on the Mono County side.
Mammoth Mountain was formed in a series of eruptions that ended 57,000 years ago. However, Mammoth still produces hazardous volcanic gases that kill trees and caused ski patroller fatalities in 2006.
Mammoth Mountain lies on the South end of the Mono-Inyo
chain of volcanic crater
s. Mammoth Mountain is also on the southwestern edge of Long Valley Caldera
, a large area that subsided after an enormous eruption 760,000 years ago. The Mammoth Mountain magmatic system is considered distinct from that of Long Valley caldera and Inyo Craters.
The volcano was formed from a long series of eruptions that started about 110,000 years ago and lasted to approximately 57,000 years ago. During this time, massive dacite
eruptions occurred roughly every 5000 years. The volcano is still active with minor eruptions, the largest of which was a minor phreatic
(steam) eruption 700 years ago.
Mammoth Mountain is composed primarily of dacite
and rhyolite
, some of which have been altered by hydrothermal activity from fumarole
s (steam vents).
out of its south flank, near Horseshoe Lake. The concentration of carbon dioxide in the ground ranges from 20 to 90 percent CO2. Measurements of the total discharge of carbon dioxide gas at the Horseshoe Lake tree kill area range from 50 to 150 ST (45.4 to 136.1 MT) per day. This high concentration causes trees to die in six regions that total about 170 acre (0.6879662 km²) in size (see photo, below).
The tree kills originally were attributed to a severe drought that affected California in the late 1980s and early 1990s. Another idea was that the kills were the result of a pathogen
or other biological infestation. However neither idea explained why all trees in the affected areas were killed regardless of age or health. Then in March 1990, a United States Forest Service
ranger became ill with suffocation
symptoms after being in a snow-covered cabin near Horseshoe Lake.
Measurements around the lake found that restrooms and tent
s had a greater than 1% CO2 concentration (toxic), and a deadly 25% concentration of CO2 in a small cabin. CO2 concentrations of less than 1% are typical and healthy in most soil
s, however soil concentrations of CO2 in the tree kill areas ranged from 20% to 90%. This overabundance of CO2 was found to be the cause of the tree kills because tree roots need to absorb O2 directly and the high CO2 level reduced available O2. Researchers also determined that Mammoth releases about 1300 short tons (1,179.3 MT) of CO2 every day. As of 2003 the concentration of carbon dioxide in soil gas at Mammoth Mountain is being monitored on a continuous, year-round basis at four sites - three at Horseshoe Lake and one near the base of Chair 19 at the ski area.
The most likely sources of the CO2 are degassing of intruded magma
and gas release from limestone
-rich metasedimentary rocks that are heated by magmatic intrusions. The remarkable uniformity in chemical and isotopic
composition of the CO2 and accompanying gases at different locations around Mammoth Mountain indicates that there may actually be a large reservoir of gas deep below the mountain from which gas escapes along fault
s to the surface. Measurements of helium emissions support the theory that the gases emitted in the tree kill area have the same source as those discharged from Mammoth Mountain Fumarole. There is evidence that the rate of CO2 discharge has been declining, with emissions peaking in 1991.
, the highest ski resort in California. Mammoth is notable for the unusually large amount of snowfall it receives compared to other Eastern Sierra peaks—about 400" annually—due to its location in a low gap in the Sierra crest. In the summer months the ski gondola
s are used by mountain bikers
and tourists who wish to get a summit view of Long Valley Caldera
directly to the east and Sierra peaks to the west, south and north.
Lava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...
complex west of the town of Mammoth Lakes, California
Mammoth Lakes, California
-History:The European history of Mammoth Lakes started in 1877, when four prospectors staked a claim on Mineral Hill, south of the current town, along Old Mammoth Road. In 1878, the Mammoth Mining Company was organized to mine Mineral Hill, which caused a gold rush. By the end of 1878, 1500 people...
in the Inyo National Forest
Inyo National Forest
Inyo National Forest is a federally administered forest in the United States. The forest covers parts of the eastern Sierra Nevada of California, and the White Mountains of California and Nevada. It contains two wilderness areas: the John Muir Wilderness and the Ansel Adams Wilderness...
of Madera County
Madera County, California
Madera County is a county of the U.S. state of California, located in the Central Valley and the Sierra Nevada north of Fresno County. It comprises the Madera-Chowchilla, CA Metropolitan Statistical Area. As of the 2010 census the population was 150,865...
and Mono County
Mono County, California
Mono County is a county located in the east central portion of the U.S. state of California, to the east of the Sierra Nevada between Yosemite National Park and Nevada. As of the 2010 census, the population was 14,202, up from 12,853 at the 2000 census...
. It is home to a large ski area on the Mono County side.
Mammoth Mountain was formed in a series of eruptions that ended 57,000 years ago. However, Mammoth still produces hazardous volcanic gases that kill trees and caused ski patroller fatalities in 2006.
Geology
Mono-Inyo Craters
The Mono–Inyo Craters is a volcanic chain of craters, domes and lava flows in Eastern California that stretches from the northwest shore of Mono Lake to the south of Mammoth Mountain. The chain is located in Mono County in the U.S. state of California...
chain of volcanic crater
Volcanic crater
A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth...
s. Mammoth Mountain is also on the southwestern edge of Long Valley Caldera
Long Valley Caldera
Long Valley Caldera is a depression in eastern California that is adjacent to Mammoth Mountain. The valley is one of the largest calderas on earth, measuring about long and wide . The elevation of the floor of the caldera is in the east and in the west...
, a large area that subsided after an enormous eruption 760,000 years ago. The Mammoth Mountain magmatic system is considered distinct from that of Long Valley caldera and Inyo Craters.
The volcano was formed from a long series of eruptions that started about 110,000 years ago and lasted to approximately 57,000 years ago. During this time, massive dacite
Dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
eruptions occurred roughly every 5000 years. The volcano is still active with minor eruptions, the largest of which was a minor phreatic
Phreatic
The term phreatic is used in Earth sciences to refer to matters relating to ground water below the water table . The term 'phreatic surface' indicates the location where the pore water pressure is under atmospheric conditions...
(steam) eruption 700 years ago.
Mammoth Mountain is composed primarily of dacite
Dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
and rhyolite
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
, some of which have been altered by hydrothermal activity from fumarole
Fumarole
A fumarole is an opening in a planet's crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The steam is created when superheated water turns to steam as its pressure drops when it emerges from...
s (steam vents).
Volcanic gas discharge
Mammoth is outgassing large amounts of carbon dioxideCarbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
out of its south flank, near Horseshoe Lake. The concentration of carbon dioxide in the ground ranges from 20 to 90 percent CO2. Measurements of the total discharge of carbon dioxide gas at the Horseshoe Lake tree kill area range from 50 to 150 ST (45.4 to 136.1 MT) per day. This high concentration causes trees to die in six regions that total about 170 acre (0.6879662 km²) in size (see photo, below).
The tree kills originally were attributed to a severe drought that affected California in the late 1980s and early 1990s. Another idea was that the kills were the result of a pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
or other biological infestation. However neither idea explained why all trees in the affected areas were killed regardless of age or health. Then in March 1990, a United States Forest Service
United States Forest Service
The United States Forest Service is an agency of the United States Department of Agriculture that administers the nation's 155 national forests and 20 national grasslands, which encompass...
ranger became ill with suffocation
Suffocation
Suffocation is the process of Asphyxia.Suffocation may also refer to:* Suffocation , an American death metal band* "Suffocation", a song on Morbid Angel's debut album, Altars of Madness...
symptoms after being in a snow-covered cabin near Horseshoe Lake.
Measurements around the lake found that restrooms and tent
Tent
A tent is a shelter consisting of sheets of fabric or other material draped over or attached to a frame of poles or attached to a supporting rope. While smaller tents may be free-standing or attached to the ground, large tents are usually anchored using guy ropes tied to stakes or tent pegs...
s had a greater than 1% CO2 concentration (toxic), and a deadly 25% concentration of CO2 in a small cabin. CO2 concentrations of less than 1% are typical and healthy in most soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
s, however soil concentrations of CO2 in the tree kill areas ranged from 20% to 90%. This overabundance of CO2 was found to be the cause of the tree kills because tree roots need to absorb O2 directly and the high CO2 level reduced available O2. Researchers also determined that Mammoth releases about 1300 short tons (1,179.3 MT) of CO2 every day. As of 2003 the concentration of carbon dioxide in soil gas at Mammoth Mountain is being monitored on a continuous, year-round basis at four sites - three at Horseshoe Lake and one near the base of Chair 19 at the ski area.
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
and gas release from limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
-rich metasedimentary rocks that are heated by magmatic intrusions. The remarkable uniformity in chemical and isotopic
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
composition of the CO2 and accompanying gases at different locations around Mammoth Mountain indicates that there may actually be a large reservoir of gas deep below the mountain from which gas escapes along fault
Geologic fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Large faults within the Earth's crust result from the action of tectonic forces...
s to the surface. Measurements of helium emissions support the theory that the gases emitted in the tree kill area have the same source as those discharged from Mammoth Mountain Fumarole. There is evidence that the rate of CO2 discharge has been declining, with emissions peaking in 1991.
Recreational use
Mammoth Mountain is home to the Mammoth Mountain Ski AreaMammoth Mountain Ski Area
Mammoth Mountain Ski Area is a large ski resort located in Eastern California, along the east side of the Sierra Nevada mountain range in the Inyo National Forest.- Description :...
, the highest ski resort in California. Mammoth is notable for the unusually large amount of snowfall it receives compared to other Eastern Sierra peaks—about 400" annually—due to its location in a low gap in the Sierra crest. In the summer months the ski gondola
Gondola lift
A gondola lift is a type of aerial lift, normally called a cable car, which is supported and propelled by cables from above. It consists of a loop of steel cable that is strung between two stations, sometimes over intermediate supporting towers. The cable is driven by a bullwheel in a terminal,...
s are used by mountain bikers
Mountain biking
Mountain biking is a sport which consists of riding bicycles off-road, often over rough terrain, using specially adapted mountain bikes. Mountain bikes share similarities with other bikes, but incorporate features designed to enhance durability and performance in rough terrain.Mountain biking can...
and tourists who wish to get a summit view of Long Valley Caldera
Long Valley Caldera
Long Valley Caldera is a depression in eastern California that is adjacent to Mammoth Mountain. The valley is one of the largest calderas on earth, measuring about long and wide . The elevation of the floor of the caldera is in the east and in the west...
directly to the east and Sierra peaks to the west, south and north.