Mount St. Helens lets off biggest steam plume yet

MOUNT ST. HELENS NATIONAL MONUMENT, Wash. — Mount St. Helens blew off a spectacular cloud of steam and ash on Tuesday, the biggest plume yet in days of rumblings and the latest indication that a larger eruption may be in the works.

Tuesday's burst sent a roiling, dark gray cloud thousands of feet above the mountain before it streamed several miles to the northeast.

U.S. Geological Survey volcanologist Jake Lowenstern said the plume had "a significant amount of ash in it" as it rose rapidly above the 8,364-foot rim of the mountain.

"The material was observed coming up from several different vents in the crater, so that could mean things are starting to break up," Lowenstern said from the USGS office in Vancouver, Wash.

The mountain has been venting steam daily since Friday amid a series of small earthquakes and volcanic tremors.

The National Weather Service issued an ashfall advisory, saying 20- to 25-mph winds could carry ash that might fall over the northeast part of sparsely populated Skamania County, which contains the St. Helens national monument.

"We have a lot of hunters in the area because it's elk season," Skamania County Undersheriff Dave Cox said.

Officials at the Coldwater Ridge Visitors Center, 8 1/2 miles north of the mountain, told the several dozen people at the center's parking lot not to drive if the plume reached them. However, the cloud trailed away to the east.

Ken Marshall drove up from Valley Springs, Calif., hoping to see an eruption.

"It's almost like clockwork," he said. "It blows in the morning and then there are earthquakes and rockfall all the rest of the day."

Scientists have said a larger eruption is likely, but there was hardly any chance of a repeat of the mountain's lethal 1980 explosion, which killed 57 people and coated much of the Northwest with ash.

Earthquakes below magnitude 3 continued into Tuesday morning, and the 1,000-foot-high lava dome within the crater had swelled by about 150 feet. Geologists believe magma beneath the crater is pushing it upward.

"It is growing a lot," said U.S. Geological Survey spokeswoman Catherine Puckett. "It is growing very rapidly."