Backgrounder: Assessing the West Coast volcano situation


WATCH: Calvin To speaks with a geologist about volcanoes on the west coast, how they’re formed, and what threat they could pose to Vancouver Island.

According to Jackie Caplan-Auerbach, associate professor of geology at Western Washington University, there are about a dozen volcanoes between northern California and southern B.C.

The “Cascade Volcanic Arc,” as they’re collectively called, has been created by the Juan de Fuca plate sliding under the North American plate.

“That’s why all of our volcanoes are sort of in a line at a certain distance from the coast,” Caplan-Auerbach said.

About half of those volcanoes are active and only two have erupted in the past century.

In 1980, Mount St. Helens erupted, killing dozens of people and destroying hundreds of homes.

“There was ash falling well east of Spokane, Washington. It really blanketed the state,” Dr. Caplan-Auerbach said. “That ash can get into things. It can foul any kind of engines. It can, in large quantities, crush buildings.”

Dr. Caplan-Auerbach says that, unlike earthquakes, volcanoes can give plenty of warning before erupting.

The warning comes in the form of volcanic earthquakes, which, while mostly too small to be felt, can be detected by instruments.

“In the case of Mount St. Helens when it erupted in 1980, we actually had several months of warning. When it erupted again in 2004, we had a couple of weeks of warning,” she said.

Even if an eruption were to occur on the west coast, Dr. Caplan-Auerbach says the lava produced would be thicker and slower moving than that in Hawaii.

She says a bigger concern in this part of the world would be a volcanic mudslide, which can happen in the absence of an eruption.


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