A restless
Aleutian volcano exploded Wednesday night and may have blown
off a slow-growing lava dome that was building for months in its summit
crater, volcanologists say.
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Smoke rises from Cleveland Volcano in the Aleutians on Aug. 8, 2011, in
this aerial photo provided by
the National Oceanic and Atmospheric
Administration.
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Cleveland Volcano, 940 miles southwest of Anchorage, probably
burped up a small amount of ash -- a potential hazard to trans-oceanic
air travel -- but the ash did not appear to reach above 20,000 feet,
said Steve McNutt, a researcher with the Alaska Volcano Observatory. Because of its remoteness, harsh
weather in the area and budget constraints, Cleveland Volcano does not
have instruments on its flanks. As a result, scientists cannot listen to
its inner rumblings. But distant seismometers and specialized
microphones detected the explosion about 7 p.m. Wednesday, according to
the observatory. The explosion caused a
displacement of air and an airwave traveled out from the volcano at the
speed of sound, McNutt said. Instruments at volcanoes 60 and 90 miles
away detected the explosion several minutes after it occurred, he said. Clouds on Wednesday and today prevented
clear satellite views, so scientists are not sure exactly how much ash
may have shot out of the 5,676-foot volcano, which makes up the western
half of Chuginadak Island. "It is the Aleutians in winter, after all," McNutt said.

Either way, the researchers do not think the volcano poses an immediate threat to air travel. McNutt thinks the explosion
blasted away a lava dome building inside the volcano's summit crater. As
the thick, pasty molten rock flows slowly into the crater, it piles up
and plugs gas vents, he explained. An explosion can occur when the gas
builds up enough pressure, McNutt said. For now, the volcanologists are
waiting for better views of the volcano to determine exactly what
happened. Scheduled satellite passes in the near future should give them
a better idea, McNutt said. If it's true that the dome was
removed, he said, the risk is lower that a larger ash- producing
explosion might affect air travel. That is, until another dome builds
up. In December, a similar event
cleared a lava dome that had been building up at Cleveland Volcano for
two months. The brief explosion blasted volcanic ash up to about 15,000
feet, the observatory said. Meantime, volcanologists are
monitoring another volcano closer to home, one that hasn't erupted for
at least 500 or 1,000 years, McNutt said. A series of small earthquakes has
been detected in recent months at Iliamna Volcano, in Lower Cook Inlet
about 110 miles from Anchorage, according to the volcano observatory.
Those earthquakes are typical for the ancient volcano and could be
related to the movement of nearby glaciers, McNutt said. Still, more
investigation, including a flight to measure gas emissions, is
warranted, he said. "Another question, which always dogs us in these situations, is if molten rock is involved," he said. - ADN.
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