Washington watches as volcano set to erupt

The eyes of geologists, disaster officials and sightseers are today focused on Mount St Helens, where a mix of volcanic gases and low-level earthquakes raised fears the mountain in Washington state might blow its top at any moment.

Some volcano experts had said an explosion would probably happen over the weekend. But as the time passed, others cautioned today that volcanic activity is difficult to predict.

“Right now, we’re thinking it’s about a 70% chance that it will erupt and a 30% chance that it just might go back to sleep,” said US Geological Survey geologist Tom Pierson today.

He said a build-up of earthquakes since a plume of steam was released on Friday indicate pressure is still mounting within the volcano. Geological Survey crews also observed a shift in the crater floor and on part of the 1,000-foot lava dome that essentially serves as a plug for magma, he said.

“Cracks are opening up so we know something is pushing up close to the surface right now,” Pierson said.

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 happens next. Barbecues were fired up and entrepreneurs sold hot dogs and coffee to people camped along the side of the road.

Hundreds of people were cleared from a popular observatory closer to the peak at the weekend following a tremor and brief release of steam. Most air traffic was prohibited within a five mile radius of the volcano.

Scientists said they do not expect anything close to the devastation of Mount St Helen’s May 18, 1980, explosion, which killed 57 people and coated much of the Northwestern US with ash.

“Of course the volcano reserves the right to change its mind,” said scientist Peter Frenzen.

The mountain’s alert was raised to Level 3, the highest possible, meaning an eruption is imminent but scientists discussed lowering their alert to indicate only that an eruption is possible.

"No one is predicting it as a sure thing,” said Bill Steele at the University of Washington’s seismology laboratory. “This could be going on for weeks.”