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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.

Lassen Hazards Assessment Published
October 01, 2012
A hazards assessment for Lassen Volcanic Center, California, is now available for download from the USGS Publications Warehouse. The Lassen region of the southernmost Cascade Range is an active volcanic area and will erupt in the future. At least 70 eruptions have occurred in the past 100,000 years, including 3 in the past 1,000 years, most recently in 1915. Although the annual probability of an eruption is small, the consequences of some types of eruptions could be severe. The hazards assessment and report presents a discussion of volcanic and other geologic hazards in the Lassen area and delineates hazards zones for different types of volcanic activity. Visit the Pubs Warehouse to download the report.

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Earthquake Swarm in the Brawley Seismic Zone
August 27, 2012
An energetic earthquake swarm (largest event magnitude 5.5) is ongoing in the Brawley Seismic Zone south of the Salton Sea in Southern California. The swarm started on Saturday August 25 with earthquake activity on a northeast striking fault zone located about 20 km (12.5 miles) south of the young volcanic center known as Salton Buttes. The most recent eruptions, which took place about 9,000 years ago, produced five rhyolite lava domes along the present-day shore of the southern Salton Sea. The Brawley Seismic Zone, located between the northern end of the Imperial Fault and the southern end of the San Andreas Fault is a tectonically active area, with numerous earthquake swarms occurring over the last several decades, most recently in 2005 and in 1981. There is no evidence to suggest the present swarm is volcanic in nature. More information on the Brawley swarm can be found on the website of the Southern California Seismic Network (a partnership of Caltech and the USGS) at http://www.scsn.org. Visit the Salton Buttes page to learn more about the Salton Buttes volcanic area.

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Summer Field Work Underway
July 24, 2012
Summer is the time when most CalVO scientists get out into the field to conduct geologic and ground-based monitoring investigations of our regional volcanoes. GPS measurements have been taken around Long Valley Caldera, mapping of volcanic units has occurred at Lassen Volcanic Center, and work is scheduled for Mount Shasta. Some of the new data will be made available in the fall, and you will find updates about that work as new website articles.

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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.}