Mammoth Mountain

Template:Short description Template:About Template:Use mdy dates Template:Infobox mountain Mammoth Mountain is a lava dome complex partially located in the town of Mammoth Lakes, California, in the Inyo National Forest of Madera and Mono counties.<ref name="SI"/> It is home to a large ski 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 produces hazardous volcanic gases that kill trees.<ref name=latimes2006/>

Geology

Mammoth Mountain is a lava dome complex in Mono County, California. It lies in the southwestern corner of the Long Valley Caldera<ref name=igarss2000/> and consists of about 12 rhyodacite and dacite overlapping domes.<ref name=volcanoworld/> These domes formed in a long series of eruptions from 110,000 to 57,000 years ago, building a volcano that reaches Template:Convert in elevation.<ref name=osti2006/> During this time, massive dacite eruptions occurred roughly every 5000 years.<ref name=Harris2005/> The volcano is still active with minor eruptions, the largest of which was a minor phreatic (steam) eruption 700 years ago.<ref name="SI"/>

Mammoth Mountain also lies on the south end of the Mono-Inyo chain of volcanic craters.<ref name=usgs2000/> The magma source for Mammoth Mountain is distinct from those of both the Long Valley Caldera and the Inyo Craters.<ref name="SI"/><ref name="Hildreth2004">Template:Cite journal</ref><ref name="LBL"/> Mammoth Mountain is composed primarily of dacite and rhyolite,<ref name="USGS_GEO_HIST"/> part of which has been altered by hydrothermal activity from fumaroles (steam vents).<ref>Template:Cite web</ref>

Volcanic gas discharge

Mammoth is outgassing large amounts of carbon dioxide out of its south flank, near Horseshoe Lake, causing mazuku in that area. Template:Source? The concentration of carbon dioxide in the ground ranges from 20 to 90 percent Template:CO2. Template:Source? Measurements in the 1990s of the total discharge of carbon dioxide gas at the Horseshoe Lake tree-kill area ranged from Template:Convert per day; this high concentration caused trees to die in six regions that total about Template:Convert in size (see photo).<ref name="usgsco2"/>

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 U.S. Forest Service ranger became ill with suffocation symptoms after being in a snow-covered cabin near Horseshoe Lake.<ref name="magmatic"/>

File:Death by Carbon Dioxide, Horseshoe Lake, Mammoth, CA 2016 (32011250720).jpg

Overabundance of carbon dioxide in the soil from a natural underground volcanic source has killed a large area of trees

Measurements around the lake found that restrooms and tents had a greater than 1% Template:CO2 concentration (toxic) and a deadly 25% concentration of Template:CO2 in a small cabin. Template:CO2 concentrations of less than 1% are typical and healthy in most soils; however, soil concentrations of Template:CO2 in the tree-kill areas ranged from 20% to 90%. This overabundance of Template:CO2 was found to be the cause of the tree-kills because tree roots need to absorb O₂ directly and the high Template:CO2 level reduced available O₂. Researchers also determined that Mammoth releases about Template:Convert of Template:CO2 every day.

As of 2023, the concentration of carbon dioxide in soil gas at Mammoth Mountain was being monitored on a continuous, year-round basis at Horseshoe Lake, according to the U.S. Geological Survey, at a site where tree root suffocation was observed.<ref>Template:Cite web</ref>

The most likely Template:Opinion sources of the Template:CO2 are degassing of intruded magma and gas release from limestone-rich metasedimentary rocks that are heated by magmatic intrusions. Template:Source? The remarkable uniformity in chemical and isotopic composition of the Template: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 faults to the surface.<ref name="usgsco2" /> 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.<ref name="LBL" /><ref>Template:Cite web</ref>

There is evidence, published in 2007, that the rate of Template:CO2 discharge has been declining,<ref>Template:Cite conference</ref> with emissions peaking in 1991.<ref name="usgs172-96" />Template:Update

Ski patrol fatalities incident

In April 2006, three members of the Mammoth Mountain Ski Area ski patrol died while on duty when a fumarole caused a snow bridge to collapse under the patrollers.<ref>Template:Cite web</ref> The 2005/2006 winter season delivered significant snow depth of Template:Convert.<ref name="History">Template:Cite web</ref> As the ski patrollers assessed the fumarole for skier safety, the perimeter snow collapsed, dropping the patrollers Template:Convert into the bottom of the fumarole, exposing them to extremely high levels of carbon dioxide.<ref name="OC3killed">Template:Cite news</ref> It is unclear if they died as a result of the fall or as a result of the gas.<ref name="OC3killed" />

Recreational use

File:Mammoth Mtn ski area (16126219736).jpg

Ski runs

Mammoth Mountain is home to the Mammoth Mountain Ski Area, founded by Dave 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 Eastern Sierra peaks—about Template:Convert annually and about 300 out of 365 days of sunshine—due to its location in a low gap in the Sierra crest.<ref name=wsc2001/> The ski area has more than Template:Convert of skiable terrain, with Template:Convert of vertical serviced by 25 lifts.<ref name=stats>Template:Cite web</ref> In the summer months the ski gondolas 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.<ref name="NYT_SKI"/> To the south of the mountain, there are a number of lakes that serve as tourist attractions in the summer. Template:Clear right

Further reading

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External links

• Mammoth Mountain Ski Area trail map
• USGS Volcano Hazards Program, Long Valley Observatory Template:Webarchive
• QTVR of tree kill area
• Mammoth Earthquake 1980 May 25 16:33, 16:49, 19:44 UTC Magnitude 6.2, 5.9, 5.9
• Template:Cite web
• Template:Cite web