Mt St Helens May Erupt Again

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By MELANTHIA MITCHELL

SEATTLE (AP) - A strengthening series of earthquakes at Mount St. Helens prompted seismologists Sunday to warn that the once-devastating volcano may see a small explosion soon.

The U.S. Geological Survey issued a notice of volcanic unrest in response to the swarm of hundreds of earthquakes that began Thursday.

"The key issue is a small explosion without warning. That would be the major event that we're worried about right now," said Willie Scott, a geologist with the USGS office in Vancouver.

The quakes were tiny at first, but on Saturday and Sunday there were more than 10 temblors of magnitude 2.0 to 2.8, the most in a 24-hour period since the last dome-building eruption in October 1986, Scott said.

In the event of an explosion, Scott said the concern would be focused on the area within the crater and the flanks of the volcano. It's possible that a five-mile area primarily north of the volcano could receive flows of mud and rock debris.

That portion of the mountain blew out during the 1980 eruption that left 57 people dead, devastating hundreds of square miles around the peak and spewing ash over much of the Northwest.

The quakes have occurred at depths less than one mile below the lava dome within the mountain's crater. Some of the earthquakes suggest the involvement of pressurized fluids, such as water or steam, and perhaps magma.

The cause and outcome of the swarm were uncertain Sunday evening. A group of scientists planned to visit the mountain Monday to collect data.

"There's been no explosions, there's no outward sign that anything is occurring. (The notice) is all based on the pattern of earthquake activity that is occurring below the dome," said Scott.

Experts believe there is "an increased probability of explosions from the lava dome if the level of current unrest continues or escalates," USGS and the University of Washington Pacific Northwest Seismograph Network in Seattle said in a joint statement.

___

On the Net:

http://vulcan.wr.usgs.gov/Volcanoes/Cascad...urrentActivity/

http://www.pnsn.org/HELENS/welcome.html

Copyright 2004 The Associated Press.
 
They say it wont be as big as the last one. But you never know what Mother Nature will do. :cheers:
 
It's probably going to just a little burp.... then again, they say that there was supposed to be an earthquake in SoCal... Still waiting.
 
By PEGGY ANDERSEN

SEATTLE (AP) - Small earthquakes rattled Mount St. Helens at the rate of one or two a minute Monday, and seismologists were working to determine the significance of some of the most intense seismic activity in nearly 20 years.

Carbon dioxide and sulfur gas samples collected above the volcano _ which erupted to devastating effect in 1980 _ will help scientists figure out what is going on beneath the 925-foot-high dome of hardened lava within the mountain's gaping crater. They want to know whether the quakes are the result of water seeping into the mountain or magma moving under its crater.

In either case, scientists will continue watching from the Cascade Volcano Observatory operated by the U.S. Geological Survey in Vancouver, Wash., about 50 miles away.

"But if it's magma, we'll be a lot more nervous," said the observatory's chief scientist Jeff Wynn.

A helicopter carried scientists and instruments over the crater Monday to assess the gases and ground deformation that would indicate pressure building below the dome.



Measurements of ground movement "will tell us whether there's any new magma coming into the system," said Seth Moran, a seismologist at the observatory. That data will not be immediately available.

Swarms of small earthquakes began Thursday and increased in frequency and magnitude until Sunday, when there were more than 10 events with a magnitude of 2 to 2.8. The quakes are at depths less than one mile below the lava dome.

By Monday, the pace was unchanged and the magnitude range had narrowed to between 0.5 and 2-plus, Wynn said.

"Since this morning, the energy releases have been slowly but steadily ramping up," he said. "We don't know what that means. ... That kind of energy hasn't been seen since 1986," when the mountain's last lava-dome-building eruption occurred.

Moran said there was potential for explosions within the crater that could throw rocks as far as the rim.

The USGS issued a notice of volcanic unrest on Sunday, citing "an increased likelihood of a hazardous event." U.S. Forest Service officials closed hiking trails above the tree line at 4,800 feet on the 8,364-foot mountain, though the visitor's center and most other trails at the Mount St. Helens National Monument remained open.

St. Helens' May 18, 1980, eruption killed 57 people, leveled hundreds of square miles of forests and dumped volcanic ash across the Northwest.

Sunday's activity was the most in a 24-hour period since the 1986 eruption, said survey geologist Willie Scott. Earthquake swarms in 1998 and 2001 did not result in any surface activity.

If there is an explosion, Scott said concern would be focused within the crater and on the upper flanks of the volcano. A five-mile area, primarily north of the volcano, could receive flows of mud and rock debris.

On Monday, a helicopter lowered a geophysicist onto the lava dome to replace a failed instrument used to measure tiny movements that indicate whether the dome is swelling, Wynn said.

While the chopper was near the dome, the pilot was in radio contact with Bobbie Myers, another geophysicist who during the 1980 blast learned to detect subtle changes in seismic monitors.

"She's known to be able to predict explosive events up to a couple of minutes ahead of time," Wynn said.

___

On the Net:

http://vulcan.wr.usgs.gov/Volcanoes/Cascad...tActivity/%und_

http://www.pnsn.org/HELENS/welcome.html
 
By GENE JOHNSON

SEATTLE (AP) - The flurry of earthquakes at Mount St. Helens intensified further Thursday, and one scientist put the chance of a small eruption happening in the next few days at 70 percent.

Jeff Wynn, chief scientist at the U.S. Geologic Survey's Cascade Volcano Observatory in Vancouver, Wash., said tiny quakes were happening three or four times a minute. Larger quakes, with magnitudes of 3 to 3.3, were happening every three or four minutes, he said.

New measurements show the 975-foot lava dome in the volcano's crater has moved 2 1/2 inches to the north since Monday, Wynn said.

"Imagine taking a 1,000-foot-high pile of rocks and moving it 2 1/2 inches. For a geologist, that's a lot of energy," Wynn said.

Wynn estimated there was a 70 percent chance the activity will result in an eruption.

Scientists did not expect anything like the mountain's devastating eruption in 1980, which killed 57 people and coated towns 250 miles away with ash. On Wednesday, they warned that a small or moderate blast from the southwest Washington mountain could spew ash and rock as far as three miles from the 8,364-foot peak.



Scientists planned to fly over the volcano again Thursday to test for gasses that could indicate the presence of magma moving beneath the volcano.

Few people live near the mountain, which is in a national forest about 100 miles south of Seattle. The closest structure is the Johnston Ridge Observatory, about five miles from the crater.

The heightened alert has drawn a throng of sightseers to observation areas. Dawn Smith, co-owner of Eco Park Resort west of the mountain, told The News Tribune of Tacoma, "It's just been crazy the past couple of days."

A sign in front of her business reads, "Here we go again."

The Geological Survey raised the mountain's eruption advisory from Level 2 to Level 3 out of a possible 4 on Wednesday, prompting officials to begin notifying various state and federal agencies of a possible eruption. The USGS also has asked the National Weather Service to be ready to track an ash plume with its radar.

In addition, scientists called off a plan to have two researchers study water rushing from the crater's north face for signs of magma. A plane was still able to fly over the crater Wednesday to collect gas samples. Negligible amounts of volcanic gas were found.

"An aircraft can move ... out of the way fast," Wynn said. "We don't want anyone in there on foot."

The USGS has been monitoring St. Helens closely since Sept. 23, when swarms of tiny earthquakes were first recorded. On Sunday, scientists issued a notice of volcanic unrest, closing the crater and upper flanks of the volcano to hikers and climbers.

Scientists said they believe the seismic activity is being caused by pressure from a reservoir of molten rock a little more than a mile below the crater. That magma apparently rose from a depth of about six miles in 1998, but never reached the surface, Wynn said.

The mountain's eruption on May 18, 1980, blasted away its top 1,300 feet, spawned mudflows that choked the Columbia River shipping channel, leveled hundreds of square miles of forest and paralyzed towns and cities more than 250 miles to the east with volcanic ash.

___

On the Net:

U.S. Geological Survey regional site: http://vulcan.wr.usgs.gov/Volcanoes/Cascad...urrentActivity/

Pacific Northwest Seismic Network: http://www.pnsn.org/HELENS/welcome.html

Eco Park: http://www.ecoparkresort.com/

Copyright 2004 The Associated Press
 
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