The potential for damaging earthquakes, landslides, floods, tsunamis, and wildfires is widely recognized in California. The same cannot be said for volcanic hazards, despite the fact that eruptions occur in the state about as frequently as the largest earthquakes on the San Andreas Fault in San Francisco. At least ten volcanic eruptions have taken place in California in the past 1,000 years—most recent is the Lassen Peak eruption of 1914 to 1917 in Northern California—and future volcanic eruptions are inevitable. Based on the record of volcanism over the last few millennia, the likelihood of another eruption occurring in California in the next 30 years is about 16 percent.
A new 2019 report, "California's Exposure to Volcanic Hazards", prepared in collaboration with the State of California Governor's Office of Emergency Services (CalOES) and the California Geological Survey (CGS), provides a broad perspective on the State's exposure to volcanic hazards by integrating volcanic hazard information with geospatial data on at-risk populations, infrastructure, and resources. The information in this report is intended to prompt follow-up site and sector specific vulnerability analysis and improved hazard mitigation, disaster planning, and response protocols.
Since 1980, there have been 120 eruptions and 52 episodes of notable volcanic unrest at 44 U.S. volcanoes. When erupting, all volcanoes pose a degree of risk to people and infrastructure. However, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location.
The USGS assesses active and potentially active volcanoes in the U.S., focusing on history, hazards and the exposure of people, property and infrastructure to harm during the next eruption. We use 24 factors to obtain a score and threat ranking for each volcano that is deemed potentially eruptable. The findings are published in the 2018 Update to the U.S. Geological Survey National Volcanic Threat Assessment.
The update names 18 very high threat, 39 high threat, 49 moderate threat, 34 low threat, and 21 very low threat volcanoes. The volcanoes are in Alaska, Arizona, California, Colorado, Hawaii, Idaho, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming, American Samoa and the Commonwealth of the Northern Mariana Islands. The threat ranking is not an indication of which volcano will erupt next. Rather, it indicates how severe the impacts might be from future eruptions at any given volcano.
The volcanic threat assessment helps prioritize U.S. volcanoes for research, hazard assessment, emergency planning, and volcano monitoring. It is a way to help focus attention and resources where they can be most effective, guiding the decision-making process on where to build or strengthen volcano monitoring networks and where more work is needed on emergency preparedness and response.
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Scientists within the USGS Volcano Hazards Program operate from within five U.S. volcano observatories. One of the primary goals of the observatories is to be an authoritative source for enlightening information about our Nation's volcanoes.
The Hawaiian Volcano Observatory (HVO), the oldest of the five, has a long history of writing regular articles about volcanic activity and scientific research on the Hawaiian volcanoes. HVO's weekly article, "Volcano Watch," entered its 27th year of publication in November 2017. The entire catalog of articles can be accessed and searched on their website. New articles are published every Thursday afternoon.
Taking lead from HVO, the Yellowstone Volcano Observatory (YVO), the newest of the five observatories, began a weekly article on the first day of 2018. This new column—the "Yellowstone Caldera Chronicles"—is posted each Monday on the homepage of YVO's website . Like HVO's Volcano Watch series, the YVO Chronicles are peer-reviewed and edited before publication.
If you are interested in learning more about a specific topic related to Yellowstone or Hawaiian volcanism, please contact us. We will certainly answer, and you may see a longer-winded answer in a future Volcano Watch or Yellowstone Caldera Chronicle article.