Does California Have Any Active or Hazardous Volcanoes?

On the news you often hear about California earthquakes, landslides, floods, and even tsunamis. But the potential for a volcanic eruption in California is not a common headline.

Northern California. Southern Cascades. Lassen Volcanic National Park's 10,457-foot Lassen Peak erupting.Photo byPublic Domain. Edited by Epic Earth

In the past 1,000 years there have been at least ten eruptions in California. The most recent was North California’s Mount Lassen in 1914. It continued its activity until 1917. Can it erupt again? The answer is yes.

As a matter of fact, scientists say that there is a 16% chance that in the next 30 years one of the volcanos in California will erupt. If you compare this to a Bay Area earthquake of 6.7 magnitude or greater on the San Andreas Fault, the probability is 22% in the next 30 years. Yet we only hear about the earthquake probabilities and not the volcanic ones.

Did you know California had so much volcanic activity? Let us know in the comments.

Are they monitoring these volcanoes?

The U.S. Geological Survey's (USGS) Volcano Hazards Program, the California Volcano Observatory (CalVO) monitors the volcanoes of California and Nevada. CalVO monitors things like background earthquakes and ground movement.

1938 Lassen Volcanic National Park Pamphlet. Cover pictures the Mount Lassen 1915 eruption.Photo byNational Park Service Public Domain

They are actively monitoring the following concerns: Mount Shasta, Medicine Lake Volcano, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region (Mammoth Mountain included), Coso Volcanic Field, Ubehebe Craters, and Salton Buttes. The observatory has placed sensors around these areas to detect any increase in activity that might be the first sign that a volcano is heading toward eruption. In addition, CalVO helps communities and government authorities understand, prepare for, and respond to volcanic activity.

There are 161 "watch list" volcanoes in the United States. Eight volcanic areas (representing 11 volcanoes) in California were identified as moderate, high, or very high threat. These are: Medicine Lake volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake volcanic field, Long Valley volcanic region (composed of Long Valley Caldera, Mono Lake volcanic field, Mono-Inyo Craters, and Mammoth Mountain), Ubehebe Craters, Coso volcanic field, and Salton Buttes.

Obsidian (volcanic glass) in the Obsidian Dome squeezes-up near Mammoth Mountain.Photo byUSGS Public Domain

California's Lassen Volcanic National Park

The source of heat for volcanism in the Lassen area is a subduction zone off the Northern California coast. The Gorda Plate is diving below the North American Plate. As the Gorda Plate melts into magna, it seeps up to form the Lassen Peak volcanic area. It is still active with boiling mud pots, stinking fumaroles, and churning hot springs. Lassen Volcanic National Park is one of the few areas in the world where all four types of volcanoes can be found (plug dome, shield, cinder cone, and strato).

Lassen Park Road with fumaroles steam.Photo byLibrary of Congress Public Domain

The Lassen region is the southernmost part of the Cascade Range. It is considered an active volcanic area. At least 70 eruptions have occurred in the past 100,000 years, including 10 in the past 1,000 years, most recently in 1915.

The record of past eruptions and the present state of the underlying magmatic and hydrothermal systems make it clear that future eruptions within the Lassen Volcanic Center are very likely.

Some of the other composite volcanoes in the Cascade Ranges are Mount St. Helens, Carter Lake (collapsed volcano), Mount Rainer, Mount Hood and many more.

Volcanic eruptions are typically preceded by seismic activity and ground deformation, and the Lassen area has a network of seismometers and Global Positioning System (GPS) stations in place to monitor for early warning of volcanic activity.

Seismic building. The stone seismograph hut at Lassen Volcanic National Park in Shasta and Lassen counties, California.Photo byLibrary of Congress Public Domain

Did you know that Lassen Peak was a volcano? Let us know in the Comments.

Mammoth Mountain Area

Hands down the Mammoth area is one of my favorite places when it comes to volcanic geology. It is one of the many places that inspired me to become a geophysicist. Over my lifetime, there has been activity in the area.

When I was young, they had to close the Mammoth Mountain ski run, “The Face of 3” due to volcanic activity. Then the trees died around Horseshoe Lake in the Mammoth area. This was due to higher-than-normal concentrations of CO₂. Scientists believe that the CO₂ was being released from a gas reservoir deep under Mammoth Mountain. It is believed that a 1989 earthquake and magmatic activity beneath the area opened channels for the gas to reach the surface.

Hot Creek Geological AreaPhoto byUSDA / U.S. Forest Service

When we were teens, some would sneak out to “Hot Creek” for a soak in the hot mineral springs. Now you are prohibited from soaking in the pools. Because the “Hot Creek” has gotten “hot” since recent geological activity. But it is still worth a visit due to its exceptional geological features and geothermal activity. Boiling water bubbling up from the creek bed, fumaroles and periodic geyser eruptions can been seen at Hot Creek now. There is a chamber of hot magma which lies about three miles below the surface in the area.

Did you know the Mammoth area was a supervolcano? Let us know in the comments.

Devils Postpile National Monument, near Mammoth Lakes. Columnar basalt from lava flow.Photo byFrank Kovalchek from Anchorage , CC BY 2.0 , via Wikimedia Commons

Why is this area so active? Because it is a huge volcanic caldera. A giant volcano’s mouth. Basically, a supervolcano like Yellowstone. But smaller. About 760,000 years ago, Long Valley Caldera was formed. An estimated 650 km³ of magma erupted.

The recent activity is likely to continue long into the future. According to the USGS, the odds of a small eruption in the area is 1 to 100 years. Massive eruptions of the size that created Long Valley Caldera 760,000 years ago are extremely rare. Scientists see no evidence that an eruption of such catastrophic proportions is brewing beneath Long Valley caldera. According to the USGS:

“Long Valley Caldera and the Mono-Inyo Craters chain form a large volcanic complex in eastern California that has had persistent earthquake activity and ground uplift in recent decades. Volcanoes have been active in the area for millions of years, and future eruptions are certain to occur. When the next eruption in the area does occur, it will most likely be small and from a site in the Mono-Inyo chain.” USGS

For additional information:

• http://volcanoes.usgs.gov/observatories/calvo
• http://volcanoes.usgs.gov

Are you curious to see how close you are to the California volcanic activity? Let us know in the comments.

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References

• https://www.usgs.gov/observatories/calvo/science/california-has-active-and-hazardous-volcanoes#:~:text=At%20least%20seven%20California%20volcanoes,they%20will%20erupt%20again%20in
• https://www.usgs.gov/observatories/calvo
• https://geonarrative.usgs.gov/calvo_exposure/
• https://earthquake.usgs.gov/earthquakes/map/
• https://www.loc.gov/resource/ppmsca.13398/
• https://www.usgs.gov/news/featured-story/eruptions-lassen-peak-california-1914-1917-a-centennial-commemoration
• https://www.usgs.gov/media/images/geologist-examining-highly-vesciculated-obsidian-obsidian-do
• https://www.fs.usda.gov/recarea/inyo/recarea/?recid=20412#:~:text=The%20higher%20than%20normal%20concentrations,time%20deep%20under%20Mammoth%20Mountain.
• https://www.fs.usda.gov/recarea/inyo/recarea/?recid=20414
• https://www.usgs.gov/volcanoes/long-valley-caldera/science/long-term-outlook-volcanic-activity-long-valley-caldera#:~:text=Geological%20studies%20of%20Long%20Valley,moat%20area%20within%20the%20caldera.
• Powell, C. Don , Designer. Lassen Volcanic National Park, Ranger Naturalist Service. Lassen Volcanic National Park California, ca. 1938. [Washington, D.C.: Department of the Interior, National Park Service] Photograph. https://www.loc.gov/item/2007676132/.
• Historic American Engineering Record, Creator, Peter Lassen, Horace Dittmar, Theodore Roosevelt, Mathias Supan, Stephen Mather, Civilian Conservation Corps, et al., Grogan, Brian, photographer. Lassen Park Road, Mineral, Tehama County, CA. Tehama County California Mineral, 1968. translated by Christianson, Justinemitter Documentation Compiled After. Photograph. https://www.loc.gov/item/ca2891/.
• Frank Kovalchek from Anchorage, Alaska, USA, CC BY 2.0 , via Wikimedia Commons