St. Helens continues to swell

0 Comments | Deseret News (Salt Lake City), Oct 8, 2004 | by Associated Press

MOUNT ST. HELENS, Wash. -- Part of the lava dome in Mount St. Helens' crater has risen 50 to 100 feet since Tuesday while earthquake activity has remained low, signs that magma is moving upward without much resistance, scientists said Thursday.

Despite the swelling, scientists said there was no reason to raise the alert level around the 8,364-foot volcano in southwest Washington.

The south side of the dome has been rising for the past week -- about 250 feet so far -- and is now nearly as tall as the dome's 1,000-foot summit, said Tom Pierson, a U.S. Geological Survey geologist.

Larry Mastin, a USGS expert in the physics of volcano eruptions, said there was an outside chance an eruption could send a plume of ash 15 miles into the air, but there was no indication of an imminent eruption that could threaten lives or property.

There's no way to tell when the magma -- molten rock -- might reach the surface, USGS volcanologist Jake Lowenstern told a news conference at the Cascades Volcano Observatory in Vancouver, Wash.

Earthquake activity remained relatively low Thursday, with about one magnitude 1 quake per minute. The volcano occasionally vented steam as water trickled down and hit hot rocks, Lowenstern said.

Since Sept. 23, thousands of small quakes have shaken the peak in Washington's Cascade range. Daily from Friday through Tuesday, St. Helens spewed clouds of steam mixed with small amounts of ash.

Seismic activity started to diminish Tuesday, and geologists said the most likely scenario for the volcano was weeks or months of occasional steam blasts and possibly some eruptions of fresh volcanic rock.

On Wednesday, USGS scientists downgraded a "volcano alert" to a "volcano advisory," indicating the probability of an eruption that could endanger lives and property had decreased significantly since Saturday, when thousands of people were evacuated from the mountain.

Still, scientists cautioned that the mountain remained restless.

"Escalation of unrest could occur suddenly and perhaps lead to an eruption with very little warning," a statement from the Mount St. Helens Joint Information Center said Thursday.

Geologists have said there is little chance of anything similar to the blast that blew 1,300 feet off the top of the peak, killed 57 people and paralyzed much of the inland Pacific Northwest with gritty volcanic ash on May 18, 1980.

On the Net: U.S. Geological Survey regional site: vulcan.wr.usgs.gov/Volcanoes/Cascades/CurrentActivity/