| Mammoth Mountain | |
|---|---|
 Mammoth Mountain from the south, withRitter Range behind | |
| Highest point | |
| Elevation | 11,059 ft (3,371 m) NAVD 88[1] |
| Prominence | 1,647 ft (502 m)[2] |
| Listing | Mountains of California |
| Coordinates | 37°37′50″N119°01′57″W / 37.630626492°N 119.032625631°W /37.630626492; -119.032625631[1] |
| Geography | |
  Mammoth Mountain  Mammoth Mountain | |
| Country | United States |
| State | California |
| Counties | |
| Protected area | Inyo National Forest |
| Parent range | Sierra Nevada |
| Topo map | USGS Mammoth Mountain |
| Geology | |
| Rock age | About 50,000 to 200,000 years |
| Mountain type | Lava dome complex[3] |
| Volcanic arc | Long Valley Caldera |
| Last eruption | 1260 ± 40 years[3] |
| Climbing | |
| Easiest route | Gondola[4] |
Mammoth Mountain is alava dome complex partially located in the town ofMammoth Lakes, California, in theInyo National Forest ofMadera andMono counties.[3] It is home to a largeski area primarily on the Mono County side.
Mammoth Mountain was formed in a series of eruptions that ended 57,000 years ago. Mammoth Mountain still produceshazardous volcanic gases that kill trees.[5]
Mammoth Mountain is alava dome complex inMono County, California. It lies in the southwestern corner of theLong Valley Caldera[6] and consists of about 12rhyodacite anddacite overlapping domes.[7] These domes formed in a long series of eruptions from 110,000 to 57,000 years ago, building avolcano that reaches 11,059 feet (3,371 m) in elevation.[8] During this time, massivedacite eruptions occurred roughly every 5000 years.[9] The volcano is still active with minor eruptions, the largest of which was a minorphreatic (steam) eruption 700 years ago.[3]
Mammoth Mountain also lies on the south end of theMono-Inyo chain ofvolcanic craters.[10] The magma source for Mammoth Mountain is distinct from those of both theLong Valley Caldera and the Inyo Craters.[3][11][12]Mammoth Mountain is composed primarily ofdacite andrhyolite,[13] part of which has been altered byhydrothermal activity fromfumaroles (steam vents).[14]
Mammoth isoutgassing large amounts ofcarbon dioxide out of its south flank, nearHorseshoe Lake, causingmazuku in that area.[citation needed] The concentration of carbon dioxide in the ground ranges from 20 to 90 percent CO2.[citation needed] Measurements in the 1990s of the total discharge of carbon dioxide gas at the Horseshoe Lake tree-kill area ranged from 50 to 150short tons (45 to 140 t) per day; this high concentration caused trees to die in six regions that total about 170 acres (0.69 km2) in size (see photo).[15]
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 apathogen 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, aU.S. Forest Service ranger became ill withsuffocation symptoms after being in a snow-covered cabin near Horseshoe Lake.[16]
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Measurements around the lake found that restrooms andtents 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 mostsoils; 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 1,300 short tons (1,200 t) of CO2 every day.
As of 2023, the concentration of carbon dioxide insoil gas at Mammoth Mountain was being monitored on a continuous, year-round basis at Horseshoe Lake, according to theU.S. Geological Survey, at a site where tree root suffocation was observed.[17]
The most likely[opinion] sources of the CO2 are degassing of intrudedmagma and gas release fromlimestone-richmetasedimentary rocks that are heated by magmaticintrusions.[citation needed] The remarkable uniformity in chemical andisotopic 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 alongfaults to the surface.[15] 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.[12][18]
There is evidence, published in 2007, that the rate of CO2 discharge has been declining,[19] with emissions peaking in 1991.[20]
 | This article needs to beupdated. Please help update this article to reflect recent events or newly available information.(July 2025) |
In April 2006, three members of the Mammoth Mountain Ski Area ski patrol died while on duty when afumarole caused asnow bridge to collapse under the patrollers.[21] The 2005/2006 winter season delivered significant snow depth of 52 feet (16 m).[22] As the ski patrollers assessed the fumarole for skier safety, the perimeter snow collapsed, dropping the patrollers 21 feet (6.4 m) into the bottom of the fumarole, exposing them to extremely high levels ofcarbon dioxide.[23] It is unclear if they died as a result of the fall or as a result of the gas.[23]
| Climate data for Mammoth Mountain 37.6279 N, 119.0338 W, Elevation: 10,541 ft (3,213 m) (1991–2020 normals) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Mean daily maximum °F (°C) | 34.7 (1.5) | 34.2 (1.2) | 37.5 (3.1) | 41.1 (5.1) | 48.7 (9.3) | 58.4 (14.7) | 66.2 (19.0) | 65.7 (18.7) | 59.8 (15.4) | 50.5 (10.3) | 41.1 (5.1) | 34.9 (1.6) | 47.7 (8.8) |
| Daily mean °F (°C) | 25.7 (−3.5) | 24.2 (−4.3) | 26.9 (−2.8) | 30.2 (−1.0) | 37.5 (3.1) | 47.0 (8.3) | 54.4 (12.4) | 53.9 (12.2) | 48.0 (8.9) | 40.0 (4.4) | 31.6 (−0.2) | 25.9 (−3.4) | 37.1 (2.8) |
| Mean daily minimum °F (°C) | 16.7 (−8.5) | 14.2 (−9.9) | 16.3 (−8.7) | 19.3 (−7.1) | 26.4 (−3.1) | 35.5 (1.9) | 42.6 (5.9) | 42.2 (5.7) | 36.2 (2.3) | 29.6 (−1.3) | 22.0 (−5.6) | 16.8 (−8.4) | 26.5 (−3.1) |
| Averageprecipitation inches (mm) | 11.46 (291) | 9.41 (239) | 8.46 (215) | 4.96 (126) | 3.11 (79) | 0.72 (18) | 0.50 (13) | 0.39 (9.9) | 0.46 (12) | 2.62 (67) | 3.99 (101) | 9.68 (246) | 55.76 (1,416.9) |
| Source: PRISM Climate Group[24] | |||||||||||||
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Mammoth Mountain is home to theMammoth Mountain Ski Area, founded byDave McCoy in 1953. Mammoth is a ski, snowboard, and snowmobile mountain during the winter months. Mammoth is the highest ski resort in California and is notable for the unusually large amount of snowfall it receives compared to other EasternSierra peaks—about 400 in (1,000 cm) annually and about 300 out of 365 days of sunshine—due to its location in a low gap in the Sierra crest.[25] The ski area has more than 3,500 acres (1,420 ha) of skiable terrain, with 3,100 ft (940 m) of vertical serviced by 25 lifts.[26] In the summer months the skigondolas are used bymountain bikers and tourists who wish to get a summit view ofLong Valley Caldera directly to the east and Sierra peaks to the west, south and north.[4] To the south of the mountain, there are a number of lakes that serve as tourist attractions in the summer.
To find the table data on the PRISM website, start by clickingCoordinates (underLocation); copyLatitude andLongitude figures from top of table; clickZoom to location; clickPrecipitation, Minimum temp, Mean temp, Maximum temp; click30-year normals, 1991-2020; click800m; clickRetrieve Time Series button.
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