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Alaska Volcano Erupts: Ash, Quakes--And More to Come

Richard A. Lovett
for National Geographic News
March 23, 2009 (Updated 10:18 p.m. ET)
 
After taunting Alaska for months, Redoubt Volcano—often called Mount Redoubt—roared into activity overnight with a series of eruptions that blew ash as high as 9.5 miles (15 kilometers) into the sky.

(See a new gallery of Redoubt Volcano eruption pictures.)

The Redoubt Volcano eruption has already sparked earthquake swarms and mudflows, and more are expected—along with perhaps a new lava dome, according to Tina Neal, a volcanologist at the Alaska Volcano Observatory in Anchorage, which monitors the 10,200-foot (3,100-meter) volcano.

The eruption could continue for days, weeks, or possibly months, Neal said.

(See a picture of Redoubt Volcano on February 3, when a steaming hole had grown to the size of a football field.)

Located about 100 miles (160 kilometers) southwest of Anchorage, Redoubt Volcano sent ash drifting north and west of the city. Anchorage itself seems to have been spared so far, thanks to the current wind pattern.

Small Alaska towns as far as 250 miles (400 kilometers) north and west of Anchorage have seen abrasive volcanic dust, and area airplanes have been grounded, Neal said.

"We have had at least five [eruptions] that lasted 4 to 30 minutes each," Neal said.

More Eruptions at Mount Redoubt?

Nobody knows what the Alaska volcano will do next, but Redoubt continues to be very restless, Neal said, producing swarms of small earthquakes and continuous tremors.

If the eruption proceeds according to form, the next step might be the formation of a lava dome, Neal said.

When Redoubt Volcano last erupted, in 1989-90, a series of such domes formed, each collapsing as it grew too large and steep to support itself.

But, Neal said, "we have no evidence of a lava dome yet."

Redoubt Volcano No Mount St. Helens

There is little chance, she added, that the volcano might produce a devastating explosion like Washington State's 1980 Mount St. Helens eruption.

More likely is that hot ash and block of lava falling on snow and glacial ice will produce mudflows.

Mudflows, in fact, have already been seen at the mouth of the Drift River, which drains the north side of the glacier-capped mountain into Cook Inlet (Redoubt Volcano-Cook Inlet map).

Whatever happens, the eruptions will be learning experiences, thanks to the volcano observatory's constant monitoring.

"When the dust settles, literally," Neal said, "we will have a lot of data to pore through."
 

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