Lull on Mount St. Helens may not last for long

By Ian Ith, Hal Bernton and Christopher Schwarzen
Seattle Times staff reporters

E-mail this article Print this article Search archive Most read articles Most e-mailed articles

Other links Monitoring Mount St. Helens Photo gallery: Mount St. Helens, then and now Mount St. Helens VolcanoCam Mount St. Helens Seismicity Information Mount St. Helens National Volcanic Monument Mount St. Helens remembered

Despite that, and another belching of steam from vents in the crater about 9:30 a.m. today, the volcano danger warning level is still reduced. And scientists continue to say St. Helens is in for an extended period of fits and starts.

"We're going to see more of this; we're going to see more explosions," said Jake Lowenstern, a U.S. Geological Survey vulcanologist.

Earthquakes have picked up slightly since a lull Tuesday night, but they are still relatively minor, coming about one a minute and never rating more than a one on the Richter scale, Lowenstern said.

The supposition is that the majority of the thick rock barring the magma's rise in the crater has been broken up, so there's less rumbling as the magma moves up.

Nonetheless, the magma is still beneath the surface, though how deep is a matter of speculation. Some scientists think it could be right under the lava dome in the crater, while others think it could be more than several hundred meters down. None has oozed to the surface yet.

The alert level remains at 2, on a 3-point scale, meaning scientists don't believe lives or property is in immediate peril.

This morning Bruce Duffe, an engineer with the Army Corps of Engineers in Portland, reiterated that a sediment dam on the North Fork of the Toutle River would be sufficient to hold back the majority of mudflows that the volcano might generate and dissipate them so that the effect to downriver towns would be no worse than a typical winter flood.

Winds today are blowing to the northeast, so any ash that might puff out of St. Helens would again drift toward small timber towns in eastern Lewis County, where a tiny dusting of ash fell this week.

Meantime, Secretary of Agriculture Ann M. Veneman arrived at Mount St. Helens this morning and was planning to tour the volcano, then hold a news conference this evening.

It's not uncommon for volcanoes to cough to life, then pause a while, then cough to life again, scientists say.
 
"We still have a volcano in a period of unrest," said Rob Harper of the state Emergency Management agency.

The mountain calmed amid a major weather change, with as much as ¾-inch of rain pouring into the crater Tuesday night, USGS officials said.

The rain helped trigger small lahars, or mudslides, overnight Tuesday that rolled north into Spirit Lake. The moisture also appeared to freshen the volcanic landscape north of the mountain with soft hues of green.

But even if the eruptions were to continue into the winter, melting snow, the scientists said they don't think lahars are a serious threat to communities in the shadow of the volcano.

The mountain is under continuous study by volcanologists, geologists, hydrologists, seismologists and other scientists who have years of collective experience tracking Mount St. Helens and other volcanoes around the world.

They say periods of quiet lasting days or weeks are not unusual as gas-rich magma works its way to the surface.

For example: Mount St. Helens' May 18, 1980, eruption, which claimed 57 lives, came after a drop in seismicity. The volcano first began rumbling nearly two months earlier, with a 4.1-magnitude earthquake, 10 times stronger than any quake in the last weeks.

The 1980 earthquakes continued until the last week of April, then subsided sharply. They started again May 8, according to Thom Corcoran, author of "Mount St. Helens: Story Behind the Scenery."

Scientists have consistently discounted the possibility that Mount St. Helens would erupt now with the ferocity of 1980. The volcano was a different mountain then. That eruption included an enormous landslide and a massive lateral blast that did much of the damage.

For now, scientists are reviewing two broad scenarios:

In one, magma would quietly ooze to the surface and rebuild the lava dome in the crater. In the other, the magma would trigger a substantial, explosive eruption, producing large ash clouds that could send dust over downwind communities.

Even with the lull, there is a sort of slot-machine psychology in play at Mount St. Helens and at the scientific command post in Vancouver, a feeling that the very second you stop watching, the next pull of the handle will bring on the jackpot.

Larry Mastin, a USGS scientist, said the thermal energy pent up inside the volcano makes him lean toward the explosive-eruption scenario.

"People should be prepared for an eruption, possibly without warning, in the next days or weeks ahead," he said.

But the question remains a topic of debate among scientists.

"There's vigorous discussion of which will occur," said Steve Malone a University of Washington seismologist. "We're having a good time guessing, but nobody is certain."

Staff reporter Ian Ith contributed to this report from Vancouver, Wash.

Hal Bernton: 206-464-2581 or hbernton@seattletimes.com; Christopher Schwarzen: 425-783-0577 or cschwarzen@seattletimes.com; Ian Ith:206-464-2109 or iith@seattletimes.com