Dome-building eruption creates eerie red glow at St. Helens

By Peggy Andersen
The Associated Press

MIKE SIEGEL / THE SEATTLE TIMES Mount St. Helens this morning from 37,000 feet.

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Low-hanging clouds and steam from the 8,364-foot volcano reflect the glow of red-hot stone, making it visible from the valley below the crater's open north side.

The emerging lava dome — a "fin" of rock that was estimated Tuesday to be between 60 and 90 feet tall and between 150 and 180 feet wide — "appears to have grown somewhat," geologist Tina Neal of the U.S. Geological Survey said today at the Cascades Volcano Observatory in Vancouver, Wash.

Scientists calculate its growth rate at about 2 to 3 cubic meters per second, said Jeff Wynn, chief scientist for volcano hazards. That's enough new rock to fill an Olympic-size swimming pool in about 15 minutes.

"Till you're actually down on it you can't imagine how huge it is," he said. The new formation has been nicknamed "the 21st century dome" by geologist Willie Scott, Wynn said.

The growth is consistent with lava continuing to extrude onto the floor of the crater, Neal said, but scientists do not yet have updated measurements. The growing mass is just behind an existing dome that began forming in the months after St. Helens erupted in May 1980.

The fin, at about 750 degrees, also has a pinkish cast "like medium roast beef," Neal said.

The eerie glow from within the crater "is entirely consistent with these kinds of temperatures," she said.

New instruments were placed on the emerging mass by helicopter Tuesday. The equipment is at risk from falling rock and other hazards, but the information they provide while they last will be helpful, Neal said.

Neal and other scientists say they don't know how long the eruption might continue, or whether it will be marked by explosive blasts of ash. In its last major eruptive phase before the 1980 blast, the mountain stirred intermittently for 57 years, starting in 1800.

Seismic levels remained low at the mountain, indicating a steady flow of magma inside the volcano, Neal said.
 
The area immediately around the mountain remained closed. The alert level remains at a mid-range "volcano advisory," but scientists have said an explosive eruption could occur with very little warning.

Explosive discharges and other abrupt changes, mostly driven by variations in the flow of gas-rich magma, occurred throughout the six-year dome-building process that followed the 1980 eruption. The top of the new dome is nearly level with the old one, which rises nearly 1,000 feet from the sloping crater floor.

The emergence of lava Monday followed 21/2 weeks of unrest — earthquakes and steam and ash bursts — that began Sept. 23.

Experts say that with no hindrance at the surface, any explosion would likely send gritty ash and steam straight up, raising concern for aircraft and cars in the area. It likely would be far less dangerous than the lateral explosion of 1980, which blasted mountaintop debris nearly 20 miles north and led to a massive landslide, killing 57 people and paralyzing much of the state with a thick layer of gritty ash.

Water from rain, melting snow and the crater glacier could cause mudflows, but the silt likely would be contained by a sediment dam west of the mountain, miles from populated areas.

Advanced Ceramics Research of Tucson, Ariz., has offered scientists the use of a 22-pound unmanned aircraft to monitor the mountain during winter weather — and at night or even during an eruption. The company was awaiting Federal Aviation Administration clearance.

The plane's instruments can measure heat, gather ash and gas samples and transmit real-time images to scientists' laptop computers.