February 1, 2009

Glacier On Alaska Volcano Melting

In the latest sign that an eruption could be imminent, further seismic activity has been detected at Alaska's Mount Redoubt, scientists reported Saturday. 

"Since late Friday afternoon, seismic activity has been relatively low at Redoubt; however, it is still above normal background levels," the Alaska Volcano Observatory said early Saturday.

"The volcano is in a state of unrest," it said.

Geologists monitoring the volcano for indications of a possible eruption noticed that a hole in the glacier on the north side of Mount Redoubt had doubled in size since Friday night, and is now roughly the length of two football fields.

Scientists with the Alaska Volcano Observatory flew close to Drift Glacier on Friday, and discovered vigorous steam being emitted from a hole on the mountain. By Saturday, they confirmed the area was a fumarole that was increasing in size at a frightening pace.

A fumarole is an opening in the Earth's surface that emits gases and steam.

The scientists also noticed water streaming down the glacier, a clear indication that heat from magma is reaching higher portions of the mountain.

"The glacier is sort of falling apart in the upper part," research geologist Kristi Wallace told the AP.

The signs of heat have fueled concerns that an eruption might be close at hand.  Such an event could send an ash cloud about 100 miles northeast toward Anchorage, Alaska's largest city, or onto areas on the Kenai Peninsula, which is even closer to the volcano on the west side of Cook Inlet.

The last eruption occurred in 1990.

Alaska's volcanoes usually begin with an explosion that can send ash 50,000 feet into the air and into the jet stream. However, there are typically warning signs because magma causes small earthquakes as it moves.

Particulate released during an eruption contains jagged edges, and can cause damage to eyes, skin and breathing passages, especially in the elderly, young children and those with respiratory problems.

It can also damage engines. A 1989 eruption sent an ash cloud 150 miles into the air, flaming out the jet engines of a KLM flight en route to Anchorage.  Although the flight carrying 231 passengers ultimately landed safely, the jet descended more than two miles before pilots were able to restart the engines.

The observatory detected a significant increase in earthquake activity below Mount Redoubt a week ago, and subsequently upgraded the mountain's alert level to orange, the stage just prior to a full eruption. 

The news that an eruption was imminent sent local citizens in Anchorage out to purchase dust masks and car air filters.

According to geologist Jennifer Adleman, the observatory has been recording quakes up to magnitude 2.1, but they were less frequent than those preceding the last two eruptions in 1989 and 1990.

"We're looking for an increase of seismicity to match the precursor activity," Wallace told the AP.

"We haven't seen that yet."


Image 1: Oblique photo of Redoubt Volcano taken during an observation flight. View is of the upper north flank of the volcano looking at the recently active fumaroles. Fumarolic activity is associated with the most recent unrest at Redoubt Volcano. The vigorous steam/gas plume is coming from a large fumarole that developed between January 28 and January 30, 2009. Exposed rock, holes in the ice, and ice collapse features are all signs of thermal activity at the summit area. Credit: Wallace, Kristi / AVO / USGS.

Image 2: Close in view of fumaroles below 1989-90 lava dome in upper Drift Glacier. These were the most vigorous fumaroles on this day. Credit: Waythomas, Chris / AVO / USGS.


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