Two UW volcano studies shed light on future risks

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by GLENN FARLEY / KING 5 News

Bio | Email | Follow: @GlennFarley

KING5.com

Posted on August 22, 2013 at 5:43 PM

Updated Thursday, Aug 22 at 6:00 PM

SEATTLE -- Two new studies involving the University of Washington are shedding new light on the internal workings and risks from volcanoes, especially the ones in the Cascade range in Washington, Oregon and Northern California.

In one, just published in the journal Geology, lead author, UW volcanologist and graduate student Sarah Gelman finds through computer modeling that molten pools of magma can sit in a molten or semi-molten state below volcanoes for longer than previously thought. And the longer that rock remains in a molten state, the higher the  silica concentration can go.

What's silica?  You know it as the main ingredient in commonplace things like beach sand and glass. But in its molten form in magma silica tends to make volcanic eruptions more explosive. In rocks from the Mount St. Helens eruption in 1980, the silica content is as high as 65 percent. The 1980 eruption was explosive -- it blew the top 1,500 feet off the mountain and killed 60 people.  

Conversely, the silica content in Hawaiian volcano eruptions is much lower, around 50 percent. The rest of the content being various metals like iron and aluminum. Hawaiian eruptions tend to consist of lava flows and do not explode like Cascade volcanoes do.

Mount St. Helens is one of the most studied volcanoes in the world. In a second study called IMUSH, which stands for Imaging Magma Under St. Helens, scientists from the University of Washington, Oregon State and other institutions plan a massive test to find out just how big the magma chamber is under the mountain.

"Mount St. Helens is kind of the pilot volcano for studies of this kind," said Alicia Hotovec-Ellis, a UW volcano seismologist and grad student taking part in the study.

That study gets underway with field work next summer, with the placement of more than 2,500 seismometers on St. Helens that will pick up seismic waves triggered by small explosions around the mountain over several days. The study will also include longer-term monitoring of the reflection of natural earthquake waves off the magma reservoir below. Hotovec-Ellis says the plan is to model the shape of the system that's feeding Mount St. Helens all the way down to Earth's hot mantle.

Both projects will continue to lay the foundation for more research to come. One of the drivers of these studies is to learn enable so scientists will better be able to predict when eruptions could happen and how big they could be.  

"The Holy Grail would be to predict an eruption and get people out so it causes no loss of life," said Gelman.

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