Posted: 10/3/2004 11:20:56 AM EDT
Updated: 01:39 PM EDT U.S. Warns of Mount St. Helens Eruption By DAVID AMMONS, AP
MOUNT ST. HELENS NATIONAL MONUMENT, Wash. (Oct. 3) - Scientists kept a watchful eye on Mount St. Helens Sunday after government officials raised the volcano's alert level, cleared hundreds of visitors from the area and warned a major eruption was imminent.
A brief release of steam, followed by a forceful tremor Saturday, signaled more seismic energy since quake activity began Sept. 23 than it has at any point since its devastating May 18, 1980, eruption, which killed 57 people and coated much of the Northwest with ash.
Updated: 01:39 PM EDT U.S. Warns of Mount St. Helens Eruption By DAVID AMMONS, AP
Click Here Broadband Only MOUNT ST. HELENS NATIONAL MONUMENT, Wash. (Oct. 3) - Scientists kept a watchful eye on Mount St. Helens Sunday after government officials raised the volcano's alert level, cleared hundreds of visitors from the area and warned a major eruption was imminent.
A brief release of steam, followed by a forceful tremor Saturday, signaled more seismic energy since quake activity began Sept. 23 than it has at any point since its devastating May 18, 1980, eruption, which killed 57 people and coated much of the Northwest with ash.
Letting Off Steam
Scientists, however, expect the impending blast to be much smaller than the 1980 explosion.
The volcano alert of Mount St. Helens was raised to Level 3, which "indicates we feel an eruption is imminent, or is in progress,'' said U.S. Geological Survey geologist Tom Pierson. He said Saturday afternoon that an explosion probably would happen within the next 24 hours.
On Friday, the volcano spewed a plume of steam and ash thousands of feet into the air, but there was a scant release of steam Saturday - a puff of white cloud, followed by a dust-raising landslide in the crater. A volcanic tremor signal that came next was what prompted the heightened alert level.
Hundreds of visitors at the building closest to the volcano - Johnston Ridge Observatory five miles away - were asked to leave Saturday. Some relocated several miles north to Coldwater Ridge Visitors Center, which officials said was safe.
Talk About It · Chat | Post Messages · Top News Boards People pitched tents alongside park roads to spend the night waiting to see what the rumbling volcano would do. Saturday was the busiest day ever at visitors' centers on the mountain, with thousands of people packing buildings, crowding parking lots and sitting alongside roads in lawn chairs.
Barbara Jardin, 53, of Camas, said she saw the plume at midday and was afraid she'd miss something if she left the area. "I just stare at it and stare at it. It's too awesome to leave,'' she said.
Interior Secretary Gale Norton, who flew over the mountain Saturday, said the seismic activity has weakened the 1,000-foot lava dome that began forming in the volcano's crater after the 1980 eruption.
"It's kind of like a big cork and the new lava will be pushing like a piston against that cork,'' USGS spokeswoman Stephanie Hanna told CNN on Sunday.
Saturday's tremor lasted about an hour before it was drowned out by a series of earthquakes - one or two a minute, with a maximum magnitude of "well over 2,'' said Tom Yelin, a USGS seismologist at the University of Washington's seismic laboratory in Seattle.
· Volcanoes: Get the info you need Norton said the chances of an eruption or lava flow have increased, and that the volcano most likely will see moderate ash eruptions.
"The greatest concern at this point is an ash plume and the spread of ash itself that might come from an explosion,'' Norton said. "This is a concern for aircraft travel.''
The growing consensus among scientists is that new magma is probably entering the volcano's upper levels, possibly bringing with it volatile gases that could lead to eruptions, said Bill Steele at the University of Washington lab.
Explosions from the crater could occur without warning, possibly throwing rock onto the flanks of the volcano, the USGS said. Still, scientists said the evacuation of the observatory was primarily a precaution in case of heavy ash, which could make it difficult to drive.
"We still feel the risk is confined to this area,'' Pierson said.
No communities are near Mount St. Helens; the closest, Toutle, is 30 miles west. Few people live near the mountain, the centerpiece of the Mount St. Helens National Volcanic Monument in the Gifford Pinchot National Forest about 100 miles south of Seattle.
The 1980 blast obliterated the top 1,300 feet of the volcano, devastated miles of forest and buried the North Fork of the Toutle River in debris and ash as much as 600 feet deep.
Scientists had believed the recent flurry of shallow earthquakes may reflect movement of magma that came up the volcano's pipe during a 1998 swarm of quakes, but Pierson said Saturday's activity suggested at least some new magma was involved, making a larger explosion more likely.
Air sampling had detected only tiny amounts of the volcanic gases that new magma produces, but scientists said the gases could be sealed inside the system or have been dissolved by water on the mountain. The volcano holds a 600-foot-deep glacier and has received several inches of rain recently.
Melting of the glacier could trigger debris flows down onto the barren pumice plain at the foot of the mountain, the USGS said, noting a "very low probability'' that downstream communities would be affected.
10/03/04 10:16 EDT
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Dont people remember what happened in 1980? Just because the USGS doesn't THINK it poses a danger doesn't meen it wont- we are not as good at predicting volcanoes as we are at hurricanes- and look how off the predictions about the last 4 hurricanes were...
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