Seven active volcanoes in California pose significant threat, USGS says

SAN DIEGO -- Seven volcanoes in California are active and pose a significant threat -- including some in Southern California, according to a new report by the U.S. Geological Survey.

The agency says the biggest threat is Mount Shasta in Northern California.

"Beautiful, big Mount Shasta and Shastina -- that, geologically speaking, is ready to go. That's a monster volcano," said Dr. Pat Abbott, a former geology professor at San Diego State University.

Abbott is familiar with volcanoes around the world, including the Salton Buttes east of San Diego County, which he says are likely to erupt in our lifetime.

Red Hill, one of the four Salton Buttes, small volcanoes on the southern San Andreas Fault at the Salton Sea, is seen on June 30 near Calipatria, California. (Photo by David McNew/Getty Images)

"Last time it erupted was about 2,400 years ago," Abbott said.

"This is not the kind of a thing that is going to be big, explosive," Abbott added. "This isn't going to be a real dangerous thing. It's not going to be big Mount St. Helens or something like that. It's also not Hawaii -- it's not something where you're going to walk up right up to it and watch the lava flows. These are probably not going to be such big eruptions that San Diego would be darkened by volcanic ash."

Abbott says there are no active volcanoes in San Diego, although millions of years ago, they did shape our landscape.

"Lots of San Diego area are made of volcanic rocks," Abbott said. "That whole Mount Miguel, Otay Mountain area, Eastidge by Helix High School, Del Cerro, Black Mountain up by Poway -- all of those are made of volcano rocks, but those were eruptions that occurred 118 million years ago, 125 million years ago."

Abbot says if there are eruptions, there will get plenty of warnings as magna tries to break through the ground and cause earthquakes.

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