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Mount Rainier threatens with fire and ice.

Looming above the skylines fo Seattle and Tacoma, Mount Rainier represents one of the greatest volcanic hazards in the United States. But scientists know too little about the mountain to prepare adequately for a future diaster, according to a report released this week by the National Research Council (NRC).

"A major volcanic eruption or debris flow could kill thousands of residents and cripple the economy of the Pacific Northwest. Despite the potential for such danager, Mount Rainier has received little study," the report says.

Rainier could cause problems even without erupting, says richard S. Fiske, a geologist at the Smithsonian Institution in Washington, D.C., who directed the study for the NCR. In the past, major sections of the mountain have simply collapsed, creating large avalanches and mudflows that swept through low-lying regions now home to 100,000 people.

The U.S. Geological Survey (USGS) mapped the geology of Mount Rainier in the 1960s, and early 1970s. Since then, however, USGS has moved on to study other Cascade volcanoes, including Mount St. Helens, which erupted ccatastrophically in 1980. Most information on Mount Rainier therefore is out of date, says Carolyn L. Driedger of the survey's Cascade Volcano Observatory in VanCouver, Wash.

Diredger, who has studied the record of mudflows -- or lahars -- at Mount Rainier, says USGS now consideres this volcano the most dangerous of the Cascade range, in part because the mountain has a thick mantle of snow and ice that can melt to from floods and lahars. The growing population along the base of the volcano compounds this threat.

Volcanologists around the world have paid more heed to the danger of lahars since 1985, when a moderate eruption in Colombia triggered a mudflow that claimed 25,000 lives. From deposits to the northwest of Mount Rainier, geologists knew that this mountain spowned a lahar 5,00 years ago that carried 40 times the volume of the Colombia flow. The most recent giant lahar swept down off Rainier roughly 200 year ago; many small ones have occurred in recent decades.

According to Fisk and his colleagues on the NRC committee, debris avalanches, lahars, and floods pose the most likley hazard at Mount Rainier. The mountain is prone to landslides because internal heat and glacial water have altered the original rock, turning it into relatively weak clay in places. The volcanic edifice could collapse during an eruption, during an earthquake, or perhaps without any obvious trigger.

Fiske notes that nothing unusual is happening at Mount Rainier at the moment. "There's no unrest. We don't want to convey any sense of that. But there are actions that can be taken now before a disaster occurs," he says.

The committee recommends that scientists adopt a multipronged appraoch, combining fundament l research, monitoring systems, and community education efforts, to reduce the hazard at Rainier.

At other sites around the world, volcanologists have used a number of different techniques to keep tabs on a dangerous mountain, Seismometers can detect movement of magma below around or landslides on the surface. Researchers can use te Global positioning System to monitor changes in the volcano's surface. Stream sensors can detect floods or lahars hours before they reach population centers.

But numerous past disasters, including the 1985 Colombian catastrophe, have taught experts that scientific information alone will not save lives. Researchers must work with social scientists, civil authorities, and the general population to prepare for the inevitable upheaval at Mount Rainier, says Fiske.
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Title Annotation:Washington volcano
Author:Monastersky, Richard
Publication:Science News
Date:May 28, 1994
Words:574
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