Thursday, January 12, 2006

Volcanic danger level downgraded in Alaska

The intensity of Augustine Volcano's seismic rumblings on Thursday fell to pre-eruption levels a day after two brief explosions spewed ash five miles into the skies over Cook Inlet, but scientists still anticipate another eruption.

The diminishing earthquakes Thursday caused the Alaska Volcano Observatory to cautiously downgrade the volcano to code orange from code red. Orange means the volcano is restless and could likely erupt. Red, the highest alert level, is used when a volcano is erupting.

Scientists are still keeping a round-the-clock watch on the fitful stratovolcano, whose past eruptions have choked the skies with ash and disrupted the state's major air routes.

"We expect this to pick up in the next day or two and show us something else," said Rick Wessels, a vulcanologist with the U.S. Geological Survey.

Observatory scientists hovered over Augustine's snowy summit in a helicopter Thursday measuring temperature levels to gauge whether magma had risen to the surface.

Another group planned a flyover to measure sulfur dioxide, hydrogen sulfide and carbon dioxide concentrations in the air above Augustine. An increase in these magmatic gases could indicate a coming eruption, said Game McGimsey, a vulcanologist with the geological survey.

They will also repair a seismic station on the volcano's uninhabited island, and check for ash in collection buckets near the volcano's base.

The 4,134-foot volcano, which is nearly 200 miles southwest of Anchorage, last erupted in 1986. Ash from a seven-mile-high column drifted over the state's most populous city and forced flights to avoid the skies over Cook Inlet.

If the volcano follows a pattern similar to 1976 and 1986 eruptions, seismic activity would increase before similar or larger explosive events, according to the observatory. However, it's possible that an explosive eruption could occur with little or no warning, the observatory said.

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