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Mount St. Helens, Mount Rainier classified as 'very high threat' for eruption

The U.S. Geological Survey is updating its volcano threat assessments for the first time since 2005 and two Washington volcanoes are ranked as high threats.
Credit: solomonjee
The Mt. St. Helens volcano post May 18, 1980 eruption. Grainy photo shot in July 1997 on film. (Photo: Thinkstock)

Washington state may not have to worry about hurricanes, but it is volcano country.

The United States has 161 active volcanoes – all in the western U.S. – but only 18 are classified as a "very high threat," the U.S. Geological Survey announced in a new volcanic threat assessment report. This is the agency's first update to the list of the nation's most dangerous volcanoes since 2005.

Those 18 are considered a “very high" threat because of what’s been happening inside them and how close they are to people.

The danger list is topped by Hawaii's Kilauea, which has been erupting this year. The others in the top five are Mount St. Helens and Mount Rainier in Washington, Alaska's Redoubt Volcano, and California's Mount Shasta.

Eleven of the 18 very high threat volcanoes are in Oregon, Washington, and California.

WATCH: Ranking Washington's most dangerous volcanoes

Of the highest threat volcanoes, Washington's Mount Rainier "has the highest number of people in the downstream hazard zone," about 300,000 people, said USGS geologist Angie Diefenbach, a report co-author.

Kilauea is a different kind of volcano than the ones here in Washington. The Hawaiian volcanoes emit lava which flows downhill, and in many cases can be outwalked. Northwest volcanoes explode.

Also see | Prepare to be on your own in a major Pacific Northwest disaster

“In the Pacific Northwest, we don’t have much development on our flanks. But our volcanoes are both explosive and covered with a lot of snow and ice and can project those hazards pretty far downstream,” said John Ewert of the Cascades Volcano Observatory in Vancouver, Washington.

Ewert is the report’s chief author.

One of those explosive threats is Glacier Peak in eastern Snohomish County. Most people don’t even know it’s there because unlike most of the other volcanos in the state, it’s not obvious like a Mount Rainier or a Mount Baker.

Even though Glacier Peak is 10,541 feet high, because of its location deep in the middle of the Cascade mountains, it’s impossible to spot from Everett or I-5. It’s considered dangerous because it can launch a lahar, a river of meltwater down rivers heading toward Puget Sound.

WATCH: 34 never-before published photos of Mount St. Helens eruption

Another concern is that Glacier Peak has only one seismometer. The earthquake detectors pick up on swarms of tiny earthquakes that can indicate magma is moving toward the surface and lead to an eruption.

The Cascades Volcano Observatory wants to install four seismometers and other equipment, but getting permits is difficult as Glacier Peak sits in a large Federally dedicated wilderness area.

The new threat assessment 'is not a forecast or indication of which volcanoes are most likely to erupt next. Rather, it is an indicator of the potential severity of impacts that may result from future eruptions at any given volcano," according to the report.

The threat assessment places volcanoes into four other threat categories besides "very high:" 39 are "high" threat, 49 are "moderate" threat, 34 are "low" threat, and 21 are "very low" threat volcanoes.

So where do Washington’s volcanoes rank on the list?

Mount Adams: Ranking 34 - Threat level high.

Mount Baker: Ranking 14 - Threat level very high.

Glacier Peak: Ranking 15 - Threat level very high.

Mount Rainier: Ranking 3 - Threat level very high.

Mount St. Helens: Ranking 2 - Threat level very high.

There is also Mount Hood, south of the Columbia River in Oregon. Mount Hood ranked number 6 on the list with a very high threat level.

“I would encourage you and others not to look just at the one through N ranking,” says report author John Ewert of CVO. “Just look at the broader categories.”

Doyle Rice of USA Today contributed to this report.

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