Fire under ice may transform Mount St. Helens' crater glacier

By Hal Bernton
Seattle Times staff reporter

CHARLIE ANDERSON Retired longshoreman Charlie Anderson, an amateur glaciologist from Federal Way, took this photo of a glacier cave below Mount St. Helens' massive crater using a one-minute exposure on his camera. The cave is about 150 feet down from the surface of the crater's northwest side. The glacier, wrapped around the crater's lava dome, has been cracked and lifted in recent days as the volcano's activity has increased.

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In recent days, the horseshoe-shaped glacier has come under enormous stress. It has been cracked and lifted by the upward movement of magma somewhere deep under the mountain. It has been pierced in at least two places by explosions of steam and ash.

The glacier — at two decades a mere infant in geologic terms — does not yet bear an official name, although scientists have been calling it "Crater Glacier." Since Mount St. Helens started rumbling again two weeks ago, it has come under scrutiny like never before.

Its fate, should larger eruptions occur, will be closely watched by those who have grown to appreciate it.

The glacier was born of the fiery May 18, 1980, blast that blew off the top of the old mountain, creating a 1.8-mile-long crater that sprouted a 925-foot dome of cooled lava in the six years that followed.

	CHARLIE ANDERSON Amateur glaciologist Charlie Anderson has made 144 trips into the crater to study and photograph the glacier and explore the caves below.

The deeply shaded area between the dome and the south crater wall proved to be a prime spot for a glacier to grow, said Charlie Anderson, a retired Federal Way longshoreman and amateur glaciologist who has tracked the glacier's growth.

"When I first predicted it would grow there, everyone thought I was nuts," Anderson recalled.

Anderson has made more than 140 trips into the crater. He has explored the glacier's subterranean network of ice caves.

Anderson said the growth has been aided by avalanches that cascade down the crater rim to pile up next to the dome. Rock fall also has helped by insulating the snow that piles up.

As a result of these favorable conditions, the glacier has advanced in recent years, even as most Pacific Northwest glaciers have retreated.

It now contains nearly as much ice as the eight glaciers that flanked the old Mount St. Helens before the big eruption, Anderson said.

When last measured, the glacier contained about 120 million cubic meters of snow and ice, said Tom Pierson, a U.S. Geological Survey (USGS) scientist in Vancouver, Wash.

The fact that it flows in both directions around the dome makes it unusual, he said. "I don't know of another one quite like this anywhere."

The events of recent days drew Anderson to mountain overlooks to observe the glacier. He has consulted with USGS scientists about the network of new cracks that have fractured its surface.

Two new vents, one bubbling and one steaming, have been nicknamed "jacuzzi" and "sauna," said Carl Thornber, another USGS scientist.

Scientists are tracking the glacier vents and the scale of the uplift for clues to a possible eruption of hot magma in the days, weeks or months ahead.

But the glacier could affect the nature of any future eruption as the ice it contains turns to steam and mixes with ash, said Larry Mastin, also with the USGS.

Mastin said the steam is quite heavy, and so could form denser columns in an eruption that would not travel as high in the air and would fall back to earth closer to the mountain.

This is just a theory, Mastin cautions — one of many under discussion as Mount St. Helens enters this puzzling new phase.

Scientists say the glacier may look very different after St. Helens is done erupting this time.

"We think if we have a magmatic eruption, it could melt some of it," Pierson said. There's a good chance it could melt in the middle, he said, leaving two separate glaciers flowing around each side of the lava dome.

"But we really don't think we could get the whole glacier melting at the same time." he added.Seattle Times staff reporter Ian Ith contributed to this report from Vancouver, Wash.

Hal Bernton: 206-464-2581 or hbernton@seattletimes.com

Copyright © 2004 The Seattle Times Company

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