Earthquakes At Mount St. Helens Collapse Dome

August 1, 2005

MOUNT ST. HELENS, Wash. - The rumblings at Mount St. Helens have been so strong, the lava dome has collapsed. Scientists are trying to figure out what's behind the recent string of stronger-than-normal quakes at the volcano.

In the last 24 hours, the seismograph has recorded three earthquakes with a magnitude at or near 3.0, and these quakes are shaking things up inside the crater. St. Helens is at it again, shaking and rattling and sending the seismograph needle into overdrive.

Compare a printout of the mountain at rest and of St. Helens in the last several weeks, and you'll notice a striking difference. "At least one 3.0 magnitude quake everyday." What do these rumbles mean? Are they a preview to the next big one? Experts are not sure.

They do know the quakes are shaping and reshaping the mountain, specifically the lava dome in the heart of the crater. Each time the dome protrudes out to a certain size, a quake comes along and the dome collapses, making way for another dome to grow.

"Now, anytime during this process, it's possible to get an actual explosion." And this is a process of the mountain slowly rebuilding itself. Each dome fills up the crater some more, and the mountain is showing no signs of slowing down.

"It's gone on longer than I thought it would. I thought it would have stopped this last spring." This mountain-rebuilding process usually happens in spurts. After all, it stopped in 1986 and didn't start up again until last fall.

At this rate, experts say the lava dome would refill the crater in two or three decades. Park rangers at Mount St. Helens say contrary to rumors, the Johnston Ridge Observatory is still open despite the recent earthquakes.

Before Collapse on July 26, 2005

After Collapse on July 29, 2005

3.3 Earthquake Rumbles Below Mt. St. Helens

August 2, 2005
The Daily News, Washington

VANCOUVER -- A 3.3-magnitude earthquake trembled beneath Mount St. Helens early Sunday morning, the latest in a series of stronger than usual quakes at the volcano.

The quake at 2:34 a.m. likely triggered the overnight collapse of large section of rock at the north end of the growing lava dome, U.S. Geological Survey scientists reported Sunday from the Cascades Volcano Observatory.

Much of the smooth surface of the ridge, which is created as rock extrudes from the vent, has now been removed by rockfalls over the past few weeks.

After years of quiet, the mountain rumbled awake last September, and in October a flow of molten rock reached the surface, marking a renewal of domebuilding activity that had stoppped in 1986.

A deadly eruption in 1980 killed 57 people and sent a river of hot mud and ash down the Toutle River Valley.

USGS and the University of Washington continue to monitor the mountain.

Scientists say a more explosive eruption, possibly dropping ash within a 10-mile radius of the crater, is possible at any time.