Mount St. Helens seismic activity changing again | Seattle Times

Mount St. Helens seismic activity changing again

By Donna Gordon Blankinship
The Associated Press


DON RYAN / AP
Cody Howell, 4, sits on his father's shoulders as Tracy Howell,
left, and Jim Howell, of Bend, Ore., hope for a view of Mount St.
Helens Saturday at Coldwater Ridge Visitors Center in Southwest
Washington. Low clouds and rain made it difficult for visitors to
see any activity on the mountain.

Scientists studying Mount St. Helens say small earthquakes have started rumbling more frequently beneath the volcano in recent days, though they're not sure what it means.

Some scientists think the change is significant, while others say it's just more of the same and that the slow, steady growth of the lava dome in the volcano's crater could continue for as long as a year.

Jeff Wynn, chief scientist for volcano hazards at the U.S. Geological Survey's Cascades Volcano Observatory in Vancouver, Wash., said the seismic and electronic signals being picked up from the volcano aren't like anything scientists have seen since the mountain reawakened 31/2 weeks ago.

Four days ago, a seismograph reported a chain of earthquakes looking like a series of heartbeats - seismic activity rising and falling. Today, a seismograph hooked up to the same part of the mountain showed what looked like a chain of pearls - steady, more frequent earthquakes but without the more dramatic rising and falling of activity.

More at the Seattle Times