California’s Next Big Threat Could Be a Volcano, Not an Earthquake: USGS

March 4, 2019 Updated: March 4, 2019

California’s next big seismic event may not be an earthquake, but a volcano.

That’s according to the U.S. Geological Survey (USGS), which released a 50-page report (pdf) last week, assigning threat levels to volcanoes across the Golden State, including moderate, high, and very high.

Most of the volcanoes are in the central and northern portion of the state.

The USGS report noted there has been 10 volcanic eruptions in the region in the past 1,000 years (USGS report)

“The potential for damaging earthquakes, landslides, floods, tsunamis, and wildfires is widely recognized in California,” the report said. “The same cannot be said for volcanic eruptions, despite the fact that they occur in the state about as frequently as the largest earthquakes on the San Andreas Fault.”

The USGS report noted there have been 10 volcanic eruptions in the region in the past 1,000 years, noting that “future volcanic eruptions are inevitable.”

The agency assigned a 16 percent chance of a small to moderate volcanic eruption in the next 30 years, reported CBS San Francisco.

Researchers said that nearly 200,000 people live, work, or travel through volcanic hazard zones in California on a daily basis.

Generalized volcanic maps (USGS)

“Of the eight volcanic areas that exist in California, molten rock resides beneath at least seven of these—Medicine Lake volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake volcanic field, the Long Valley volcanic region, Coso volcanic field, and Salton Buttes—and are therefore considered ‘active’ volcanoes producing volcanic earthquakes, toxic gas emissions, hot springs, geothermal systems, and (or) ground movement,” said the report.

Mount Shasta, one of the most iconic peaks in California, has a very high threat level. Meanwhile, about 100,000 people live, work, or travel near the volcano.

In the event of an eruption, not only humans will be affected, but crops, livestock, and other animals.

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“Exposure of agricultural crops, pastures, and livestock to volcanic ash fall can be serious, even for a light dusting. Ash fall on forage most commonly results in digestive tract problems in livestock, including gastrointestinal tract obstruction,” the report said.

The USGS, in its report, said it will identify specific volcanoes to monitor habits.

“This will require the collective efforts of scientists, land managers, civil authorities, lifeline operators, and communities,” the USGS report concludes. “Only together can California successfully manage volcanic risk and continue to enjoy the beauty and benefits of a geologically dynamic state.”

Areas in California that could be directly impacted by volcanoes (USGS)

“The next step in reducing volcanic risk involves assessing site- and sector-specific vulnerabilities and developing mitigation strategies,” added the report. “This will require the collective efforts of scientists, land managers, civil authorities, lifeline operators, and communities.”

Magaret Mangan of the California Volcano Observatory said the USGS report isn’t a doomsday scenario, CBS San Francisco reported.

Threat List

Here is a list of the volcanoes and their threat risks:

Medicine Lake Volcano:
Most recent eruption: 950 years ago
Nearby towns: Malin, Merrill, Tulelake, Klamath Falls (OR)
Threat Potential: High

Mount Shasta:
Most recent eruption: 200-300 years ago
Nearby towns: Weed, Mount Shasta, Edgewood, Dunsmuir
Threat Potential: Very High

Lassen Volcanic Center:
Most recent eruption: Between 1914 and 1917
Nearby towns: Mineral, Viola
Threat Potential: Very High

Clear Lake volcanic field:
Most recent eruption: about 10,000 years ago
Nearby towns: Clearlake, Kelseyville, Lakeport, Lucerne
Threat Potential: High

Coso volcanic field (160 miles north of Bakersfield):
Most recent eruption: 40,000 years ago
Nearby towns: Olancha, Pearsonville
Threat Potential: Moderate

Long Valley Caldera volcanic region:
Most recent eruption: 16,000-17,000 years ago
Nearby towns: Mammoth Lakes
Threat Potential: Very High

Salton Buttes:
Most recent eruption: about 1,800 years ago
Nearby towns: Westmorland, Calipatrica, Niland, Brawley
Threat Potential: High