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Thar She Finally Blows – Cleveland Volcano Spewing 15,000 Feet of Ash

29/12/2011

The Alaska Volcano Observatory said satellite images showed Cleveland Volcano had spewed ash 15,000 feet (4,572 meters) into the air in a cloud that moved east-southeast. U.S. Geological Survey scientist-in-charge John Power called it a small explosion.

“It’s not expected to cause a disruption to big international air carriers,” he said.

But the event drew strong interest from air carriers.

“Any time you put an ash cloud up into the atmosphere, the airlines, the air carriers, air freight companies — it’s a major concern,” Power said.

The ash cloud was significant enough to raise the alert level from yellow, representing elevated unrest, to orange, representing an increased potential of eruption, or an eruption under way with minor ash emissions or no emissions.

Cleveland Mountain is a 5,675-foot (1,729-meter) peak on uninhabited Chuginadak Island about 940 miles (1,512 kilometers) southwest of Anchorage.

Scientists in July noted increased activity in the crater at the summit of the volcano. Satellite images showed lava building and forming a dome-shaped accumulation.

Chris Waythomas of the USGS said in September that lava domes form a lid on a volcano’s “plumbing,” including the chamber holding the magma. When they grow big enough, lava domes can become unstable and will sometimes collapse. When the magma chamber decompresses it can lead to an explosion as the conduit inside the volcano suddenly becomes unsealed and gases escape.

Radar images earlier this month showed the dome had cracked and subsided, Power said.

The Federal Aviation Administration and the airline industry get concerned for trans-Pacific flights when an ash cloud has the potential to exceed the 20,000-foot (6,096-meter) threshold, as Cleveland Volcano has done in the past.

Cleveland Volcano’s last major eruption was in 2001. It has had bursts of activity nearly every year since then, and the ash cloud Thursday was not out of character.

“It’s not unexpected for a volcano like Cleveland to do things like this,” Power said. “Unfortunately, Cleveland is one of those that is so remote, we have no on-ground monitoring or instrumentation there, so it’s hard for us to pinpoint things any more accurately than we can do with satellite imagery.”

The observatory Thursday morning had no satellite images of the crater after the eruption.

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