With 8 threatening volcanoes, USGS says California deserves close monitoring

JAKE ELLISON, SPECIAL TO SEATTLEPI.COM

Mount Shasta looming over the town of Weed in the evening. Photo: USGS

With the world’s top volcanologists heading to Portland, Ore., on Aug. 14 for the first international volcanology assembly held in the U.S. since 1989, the many famous, prominent and dangerous volcanoes of the West Coast will be the subject of field trips and much discussion.

Throughout the Cascade Range to southern California, the West Coast is home to most of the country’s highest-threat volcanoes, as ranked by the United State Geological Survey. And California has its share.

While Mount Shasta unsurprisingly tops USGS’s list of very-high threat volcanoes in California, there are seven other volcanic areas in the state that are also young, nervy, jacked up on magma and “likely to erupt.”

Scientists know from geophysical and geochemical research that these volcanoes have molten rock, magma, “in their roots,” said Margaret Mangan, Scientist-in-Charge at the California Volcano Observatory. “I call them the watch-list volcanoes.” 

USGS caption: Volcanoes of very high to low threat are scattered throughout California, from the Oregon border (north) to Mexico (south). Other older volcanoes in California are of less concern. California’s volcano watch list is subject to change as new data on past eruptive activity are collected, as volcanic unrest changes, and as populations in threatened areas grow or decline. Photo: USGS

Photo: USGS

USGS caption: Volcanoes of very high to low threat are scattered throughout California, from the Oregon border (north) to Mexico (south). Other older volcanoes in California are of less concern. California’s volcano watch list is subject to change as new data on past eruptive activity are collected, as volcanic unrest changes, and as populations in threatened areas grow or decline.

On watch

As listed by the California observatory, the eight fall into three danger categories:

  • Very-high threat: Mount Shasta, Lassen Volcanic Center and Long Valley Volcanic Region
  • High threat: Clear Lake Volcanic Field, Medicine Lake Volcano and Salton Buttes
  • Moderate threat: Ubehebe Crater and Coso Volcanic Field

In 2005, a national team led by John Ewert, a volcanologist with the USGS Cascades Volcano Observatory, established a system for deciding which of the United States’ 169 young volcanoes are the most dangerous and most in need of monitoring. In the “Framework for a National Volcano Early Warning System,” Ewert’s team identified 57 priority volcanoes in the U.S.

Among the 18 “very high threat volcanoes,” 11 are along the Cascade Range in three states (Alaska and Hawaii have the others):

  • California: Lassen Volcanic Center, Long Valley Caldera, Mount Shasta
  • Oregon: Crater Lake, Mount Hood, Newberry, South Sister of The Three Sisters
  • Washington: Baker, Glacier Peak, Rainier, St. Helens

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