Mount St. Helens lets off steam, ash with 'big burp'

MOUNT ST. HELENS, Wash. -- Mount St. Helens, the volcano that blew its top with cataclysmic force in 1980, erupted for the first time in 18 years Friday, belching a huge column of white steam and ash after days of rumblings under the mountain.

Small earthquakes resumed within hours of the blast, suggesting pressure inside the mountain was rebuilding. Scientists said there could be more steam eruptions soon.

The noontime eruption cast a haze across the horizon as the roiling plume rose from the nearly 1,000-foot-tall lava dome, forcing Alaska Airlines to cancel flights and divert others around the ash.

When Pam and LynnMorret of Vancouver got to within five miles of the Johnston Ridge Observatory on Friday, they pulled to the side of the road and saw what they had been coming for: an ashen-white cloud billowing from the volcano's crater.

"It was like a big burp," said Pam Morret, 49.

Scientists had been predicting just such an eruption for days because of thousands of earthquakes and signs that the rock inside the crater was expanding rapidly.

The eruption was nowhere near what happened 24 years ago, when 57 people were killed and towns up to 250 miles away were showered with rock and ash.

About 20 minutes after Friday's eruption, the mountain calmed and the plume began to dissipate. The ash appeared to pose no threat to anyone, but scientists warned that people living southwest of the mountain might notice a fine film of ash on their cars. No evacuations were ordered, and there was no sign of any lava oozing from the volcano.

Few people live near the mountain, about 100 miles south of Seattle. The closest structure is the observatory.

"It wasn't lava-y, so I wasn't scared," said Lorain Weatherby, who was working a snack bar down the road from St. Helens. "It was like a big white cloud."

For the past week, scientists have detected thousands of earthquakes of increasing strength -- as high as magnitude 3.3 -- suggesting another eruption was on the way. Steam frequently rises from the crater, but the 8,364-foot peak had not erupted since 1986.

"This is exactly the kind of event we've been predicting," said U.S. Geological Survey scientist Cynthia Gardner.

The earthquakes quit after the eruption, said Jeff Wynn, another USGS scientist.

He called the eruption a "throat-clearing."

"It's dead -- bone-still right now," he said. "There's nothing happening at this stage, so this may have been a single event. But the history of the volcano suggests it could be an opening salvo and we'll see more events like this."

USGS seismologist Bob Norris said magma could be moving underground and he would not be surprised to see more explosions in the next days or weeks.

"The monitoring will definitely continue on a very intense scale until we can determine that the thing has really gone back to sleep," said Tom Pierson, a USGS geologist.

Mike Fergus, a spokesman with the Federal Aviation Administration in Seattle, said the plume had reached 16,000 feet in altitude.

Alaska Airlines canceled five flights scheduled to take off from Portland International Airport in Oregon, but quickly resumed its normal schedule, said spokesman Sam Sperry.