"Something's got to give" on rattling by St. Helens

By Sandi Doughton
Seattle Times staff reporter

HARLEY SOLTES / THE SEATTLE TIMES University of Washington seismographs show almost continuous swarms of earthquakes shaking Mount St. Helens yesterday. Steve Malone, a research professor in Earth and space sciences, studies the readings. At the upper right, almost black, is the current graph for Mount St. Helens; below it, showing no activity, is the one for Mount Rainier.

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Other links Mount St. Helens Seismicity Information Mount St. Helens National Volcanic Monument

Early last week, the pages were blank, except for an occasional, tiny blip. Yesterday, they were almost solid black, each dark scrawl representing another small earthquake from beneath the volcano.

"It's continuous," said UW seismologist Steve Malone. "We know there's a lot of rock breaking, and sooner or later something's got to give."

When it does, the result could be small explosions or eruptions, possibly accompanied by an outpouring of lava onto the 925-foot dome that has built up in the crater since the volcano's massive eruption in 1980, scientists say. But the fact that volcanic gases are not escaping from the mountain in high levels means that fresh magma has not been welling up from deep underground, said Willie Scott, a volcanologist at the U.S. Geological Survey's Cascades Volcano Observatory in Vancouver, Wash. And in the absence of new magma, any eruption will not be major.

	AP, 2003 A 925-foot dome has built up in the crater of Mount St. Helens, shown from above, since the volcano's massive eruption in 1980.

"That makes us think we're not in a situation where, imminently, we could have a large, sustained, explosive eruption," Scott said.

Field crews spent the day yesterday placing instruments around the volcano to detect any bulging that would be expected if magma does begin to move upward. Preliminary readings should be available today, Scott said. Some of the instruments will deliver continuous, real-time data from fixed stations, while others will be moved around from place to place, to collect information over as many points as possible.

As recently as last month, instruments already deployed around the volcano showed no evidence of any bulging, Scott said. In the two months before the May 18, 1980, eruption, the mountain's northern flank bulged outward more than 200 feet.

Monitor the volcano The Mount St. Helens live Web camera is back in action after more than a year's down time because of technical glitches. Pictures are taken from the Johnston Ridge Observatory five miles from the crater and updated every five minutes. The site is: www.fs.fed.us/gpnf/volcanocams/msh/

Convinced the volcano was already going off yesterday, many people around the region called the volcano observatory to report what they thought were eruption plumes. What they really saw were wisps of clouds or dust from rockfalls in the crater, Scott said.

State and regional emergency planners participated in a conference call with scientists yesterday to get an update on the volcano's status and review the emergency-response plan written after the 1980 eruption killed 57 people, destroyed 200 homes and unleashed the biggest landslide in recorded history.

Although the plan has been updated in recent years, some of those on the conference call couldn't remember where their copies were, Malone said.

	HARLEY SOLTES / THE SEATTLE TIMES In the top graph, University of Washington seismographs show swarms of earthquakes shaking Mount St. Helens. The chart below it graphs the quieter readings from Mt. Rainier.

"It's been awhile," he laughed.

Scientists say any hazards from a small explosion, eruption or mudflow would be confined to the mountain's unpopulated flanks.

However, it's likely the mountain also will throw up an ash plume, which could kill the engines of any aircraft flying in the area, Scott said. If a plume occurs, the volcano observatory would notify the National Oceanic and Atmospheric Administration and the Federal Aviation Administration, which would reroute air traffic away from the drifting plume.

Mount St. Helens has rumbled several times since 1980, with thick, pasty magma pouring out and creating the lava dome that now sits inside the lopsided crater. The last lava outpouring was in 1986.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com

Copyright © 2004 The Seattle Times Company

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