Mount St. Helens N.M., Wash. Mount St. Helens stewed in volcanic gases and low-level earthquakes Sunday, with crowds of eager tourists hoping to glimpse an eruption that scientists said could happen immediately or take a few weeks.
A second long tremor early Sunday and an increase in volcanic gases strongly suggest magma is moving inside, researchers from the U.S. Geological Survey said. The mountain's alert was raised to Level 3, the highest possible, after a volcanic tremor was detected Saturday for the first time since before the mountain's 1980 eruption.
"I don't think anyone now thinks this will stop with steam explosions," geologist Willie Scott said Sunday at the Geological Survey's Cascades Volcano Observatory in Vancouver, Wash., about 50 miles south.
But Scott said scientists discussed lowering their alert from a Level 3 "volcano advisory," which indicates eruption is imminent, to Level 2 "volcanic unrest," which indicates an eruption is possible. They needed more data before making any change, he said.
"What we haven't gotten back today yet is a lot of field measurements -- there's a gas flight going on, a flight to use thermal imaging to look at the (lava) dome, GPS data needs to be downloaded," Scott said Sunday. "There's a lot of work that needs to be done. That will occur overnight and tomorrow morning."
Scientists said they do not expect anything close to the devastation of the May 18, 1980, explosion, which killed 57 people and coated much of the Northwest with ash.
"Of course, the volcano reserves the right to change its mind," said monument scientist Peter Frenzen with the U.S. Forest Service, which operates the park.
Some experts had said Saturday that an explosion would probably happen within 24 hours. But as the hours passed, others cautioned that the timing was difficult to predict.
"No one is predicting it as a sure thing," said Bill Steele at the University of Washington's seismology lab in Seattle. "This could be going on for weeks."
Crowds gathered along a park road at what was said to be a safe distance -- about 8.5 miles from the mountain -- to see what happened next. Barbecues were fired up and entrepreneurs were selling hot dogs and coffee to people camped along the side of the road in lawn chairs and pickup beds.
Hundreds of people were cleared from a popular observatory closer to the peak Saturday following a tremor and brief release of steam.
The mountain was outwardly quiet at midday. Clouds of dust rose occasionally, caused by rockfall from the towering canyon walls. But earthquakes were occurring "multiple times per minute," Steele said, peaking every few minutes at magnitudes as high as 3.
Seismic activity became more sporadic over the day, said seismologist Tony Qamar at the University of Washington's seismic lab in Seattle.