St Helens belches steam as fears of explosion persist
It was not immediately clear how large yesterday's emission was, or whether it contained ash, but US Geological Survey geologist Willie Scott said any ash would fall mostly in the crater and not threaten any structures.
The steam burst blanketed the top of the mountain in a white cloud and followed a similar blast and 20-minute tremor late Sunday.
A drumbeat of earthquakes since a plume of steam was released on Friday indicated that pressure was mounting within the mountain.
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," Geological Survey geologist Tom Pierson told NBC's Today show yesterday.
Scientists have said they do not expect anything close to the devastation of Mount St Helens' May 18, 1980, explosion, which killed 57 people.
The mountain's alert was raised to Level 3, the highest possible, after a volcanic tremor was detected Saturday.
Crowds have gathered along park roads at what was said to be a safe distance about 8.5 miles from the mountain to see what happens next.
Most air traffic was prohibited within a five-mile radius of the volcano.
The 1980 blast obliterated the top 1,300 feet of the volcano, devastated miles of forest and buried the North Fork of the Toutle River in debris and ash as much as 600 feet deep.
This time, the main concern was a significant ash plume carrying gritty pulverized rock and silica that could damage aircraft engines and the surfaces of cars and homes.
Many spectators couldn't wait out the mountain. Sunday's sunset brought a mass exodus.
"Our attention span is about like this," said James Wilder, aged 25, of Aberdeen, holding his forefinger and thumb about one-quarter of an inch apart. "We've been here five hours and we need to leave pretty soon."
