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California Volcano Observatory's mission
As a part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada.

Automated Volcanic-Gas Sniffer Installed at Mammoth Mountain Fumarole
August 12, 2014
In July 2014, USGS Scientists Peter Kelly (Cascades Volcano Observatory) and Stuart Wilkinson (California Volcano Observatory) installed an automated volcanic-gas monitoring station on Mammoth Mountain, located on the SW rim of Long Valley Caldera (CA). The station tracks the temperature and concentrations of carbon dioxide and other gases at a steaming vent high on the north flank of the mountain known as Mammoth Mountain Fumarole. Temperature and gas composition often fluctuate with earthquake activity under the mountain, probably because shaking opens new pathways for heat and gas to flow towards the surface. The new gas monitor will help scientists track these changes in near real-time. The station will be deployed for the summer months and retrieved before deep snow blankets the mountain.

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Investigating Past Eruptions of Mono Craters
July 03, 2014
CalVO geologist Mae Marcaida examines thin layers of volcanic ash sandwiched between thick beds of sediment deposited by ancestral Mono Lake in eastern California. Each ash layer is evidence of a past explosive eruption of the Mono Craters, which began erupting about 65,000 years ago just south of present-day Mono Lake. Marcaida and her colleagues use the chemistry of magnetic minerals (titanomagnetites) found in the ash to uniquely "fingerprint" each layer and link it to one of the more than 30 eruptive centers that form the Mono Craters chain. For more information about the Mono Craters ash study see: Geochemical fingerprinting of Wilson Creek tephra layers (Mono Basin, California) using titanomagnetite compositions

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Small Earthquake Swarm
June 27, 2014
A swarm of small earthquakes (magnitudes less than 2) occurred at a depth of 6-7 km (about 4 miles) beneath Highway 203 in Mammoth Lakes, California midway between the water treatment plant and the Highway 395-203 junction, June 27, 2014. The swarm began at 4:50 AM and continued with sporadic activity through the morning hours. As of 1:50 PM it appears to have largely died away. We detected no ground deformation associated with this activity, and it poses no immediate hazard.

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High to Very High Threat Potential ¹
Clear Lake Volcanic Field
Lassen Volcanic Center
Long Valley Caldera
Medicine Lake
Mono-Inyo Chain
Mount Shasta
Salton Buttes
Moderate Threat Potential ¹
Coso Volcanic Field
Soda Lakes (NV)
Ubehebe Craters
Low to Very Low Threat Potential ¹
Brushy Butte
Eagle Lake Volcanic Field
Golden Trout Creek Volcanic Field
Lavic Lake Volcanic Field
Silver Lake Volcanic Field
Tumble Buttes
Twin Buttes

^{1. View the threat rankings of US Volcanoes.}