Lava Dome Surges at Mount St. Helens

Jan. 31, 2005 -- -- The new lava dome at Mount St. Helens has grown more over the past three months than it did in the six years following the massive explosion of 1980 that sent volcanic ash circling the globe.

The dome is continuing to build, though geologists with the U.S. Geological Survey say its growth has slowed over the last several weeks. An "explosive type of event" that lasted for 18 minutes on Jan. 16 has added to the fascination with which scientists have been monitoring the mountain in southwestern Washington state.

"It's an incredible laboratory," said John Pallister, a geologist with the USGS' Cascades Volcano Observatory. "At the same time that as a scientist you're excited about it, you're intrigued by it and you're drawn to it, as a public employee you're always reminded of your duty not to overstate or understate any risks or dangers that it might pose."

After all the rumblings and spurts of steam at the volcano last fall, geologists say they are not sure what the dome's rapid growth means -- beyond one obvious fact.

"This volcano is not sleeping -- it is an active volcano," said Carolyn Bell of the USGS. "What it is going to do at this point, we don't know."

The explosion that occurred earlier this month destroyed a camera and a "spider," a device used to measure the growth of the dome, that had been put in place just 36 hours earlier.

"It was a new kind of explosive event, of a kind we haven't seen since October," Pallister said. "We're keeping an eye out for more of that type of activity."

Because the explosion occurred on a cloudy day it went largely unnoticed except by those whose business it is to keep tabs on the mountain.

"If it had happened in the middle of a blue-sky day there would have been a lot more focus on it, I think," he said.

Meter-wide boulders were shot into the air by the explosion and then fell back to Earth, gouging holes in the crater floor. Ash coated much of the crater.