Redoubt oozes lava, pressure builds

DOME: Buildup may collapse creating new round of eruptions.

May 30, 2009 

The Redoubt volcano lava dome has been slowly growing since April 4. This picture was taken from the northwest on Tuesday.

RICK WESSELS PHOTO COURTESY OF THE ALASKA VOLCANO OBSERVATORY

Since Mount Redoubt's last explosion in April, it has quietly continued to ooze lava from its vent, creating a massive hardened dome that could blow at any moment and unleash another ash fall on Southcentral Alaska.

Or maybe not.

The volcano's dome, roughly the size of nine football fields, has formed a precarious plug over its steaming vent, scientists say. That's kept ash from spewing into the atmosphere and has perhaps led many to believe the volcano's rumblings are over. But if the dome cracks or collapses, as scientists believe it likely will, ash could once again blast to tens of thousands of feet into the atmosphere and ground airplanes during Alaska's busy summer tourist season.

A second worry is that a cracked dome, accompanied by another explosion, would allow hot gas and rock to blast down the mountainside, which would melt snow and ice and once again flood the Drift River valley, as it did in late March.

Scientists estimate the amount of lava comprising the hardened dome is so massive it could fill 11 Louisiana Superdomes. It is roughly as thick as a 65-story building.

Melissa Pfeffer, an atmospheric chemist with the Alaska Volcano Observatory and part of the science team to last fly over the volcano, on May 26, said, "It's huge. It's tremendous."

At the top it's silky, she said, then rough and boulder-like at the bottom. It smelled, she said, of a combination of burnt matches and rotten eggs.

"The whole thing is beautiful," she said.

Another helicopter Pfeffer was watching from her flight just disappeared like a speck against the backdrop of the gray and brown mass, she said. "Compared to the dome, your eye couldn't pick it out."

Alaska lava is not like Hawaii lava or probably what most people picture as lava, said geologist Allison Payne of the volcano observatory. It's not as fluid. It's thick and sticky, she said.

"It's like squeezing a tube of toothpaste and having that toothpaste slowly ooze out and build up," she said. "So it does flow but on a very long time-scale."

Gravity or the building of pressure beneath the dome could make it collapse, scientists say.

The lava has been building up for two months. The last time the volcano erupted in 1989 and 1990, a similar dome lasted 36 days before it collapsed and unclogged the vent. "Based on Redoubt's past activity, this is pretty unstable," Payne said.

This eruption has shown similar patterns to the one almost two decades ago, which is why scientists eagerly anticipate more rumblings, Payne said. But when it could blow is anyone's guess. "It could happen in 10 minutes or a month or not at all," she said.

And as long as the magma, which turns to lava when it hits the air, continues to seep out of the volcano, scientists will continue to staff the AVO headquarters every hour of every day, Payne said.

That demand has continued to strain the observatory staff. Additional scientists have been brought in from around the country, including Hawaii and Washington, to keep up with the field work and monitor the seismic data, weather, satellite data, radar imagery and thermal anomalies.

The biggest threat of an explosion would be to the Drift River oil terminal 22 miles down river from Redoubt. Most of the crude oil in the tanks was moved by early May.

Mark Lang, owner of Lake Clark Inn at Port Alsworth, is about 50 miles from the volcano. It's coming up on his busy summer season and he's watching the volcano. The tourists, he said, are excited about it.

"It's more of a fun concern than anything else," he said.


Find Megan Holland online at adn.com/contact/mholland or call 257-4343.


Redoubt volcano timeline

Jan.-Feb. 1966 Volcano produces six explosions.

Dec. 1967-April 1968 Volcano produces five explosions.

Dec. 1989-March 1990 Volcano produces 23 explosions. The longest hiatus between explosions was 36 days.

Jan. 25, 2009 With seismic activity increasing, Alaska Volcano Observatory raises alert level to orange, expecting an eruption within days to weeks.

March 10 AVO downgrades alert level to yellow because of decreased seismic activity.

March 15 AVO raises alert level to orange.

March 22 Eruption. Several explosions occurred in subsequent days, including blasts on March 28 that dusted much of Southcentral, including Anchorage, with a coating of ash.

April 4 Last major explosion destroying the lava dome that had grown in late March early April. Ash plume reaches 65,000 feet.Redoubt volcano timeline

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