Volcano ash cloud covers 400 miles
Strong winds March 28 pushed an ash cloud from an Alaska volcano into the heart of the state. The ash grounded flights and limited travel to western and northern communities off the road system.
Pavlof Volcano is one of Alaska's most active volcanoes and is 625 miles southwest of Anchorage. It is on the Alaska Peninsula. That's the finger of land that sticks out from mainland Alaska toward the Aleutian Islands.
The volcano in the 8,261-foot mountain erupted about 4 p.m. March 27. It spit out an ash cloud that rose to 20,000 feet.
Lightning over the mountain and pressure sensors indicated eruptions continued overnight. By 7 a.m. March 28, the ash cloud had risen to 37,000 feet. Winds to 50 mph or more had stretched it over more than 400 miles into interior Alaska.
"It's right in the wheelhouse of a lot of flights crisscrossing Alaska," said geologist Chris Waythomas, of the U.S. Geological Survey. The USGS is part of the Alaska Volcano Observatory, along with the University of Alaska and the state Division of Geological and Geophysical Surveys.
Volcanic ash is angular and sharp and has been used as an industrial abrasive. The powdered rock can cause a jet engine to shut down so some flights were canceled. USGS geologists have compared it to flying into a sand blaster.
An eruption of Mount Redoubt in December 1989 sent out an ash cloud 150 miles. The ash flamed out the jet engines of a KLM flight carrying 231 passengers to Anchorage. The jet dropped more than two miles before pilots were able to restart the engines and land safely.
"We just simply will not fly when ash is present," Egan said.
Waythomas had received no reports of ash falling in communities. The closest community, Cold Bay, is 37 miles southwest of the volcano. That is opposite of where the wind was blowing ash.
Geologists call Pavlof an open-system volcano, Waythomas said.
"The pathways that magma follows to the surface are pretty open in a volcanological sense," Waythomas said. "They can convey magma and gas very easily. Magmas can move to the surface whenever they feel like it, more or less."
The movement comes with little shaking of the ground. And the lack of earthquakes as an early warning of an eruption "makes us go crazy monitoring them," Waythomas said.
The volcano is about 4.4 miles in diameter. It has had 40 known eruptions. Its conical, nearly symmetrical shape indicates its eruptions tend to be less violent than the kind that blows tops off mountains.
"It can erupt for periods of hours to days. Or it can go on for much longer periods of time," Waythomas said. "It won't erupt continuously for many months or a year. It will be intermittent. But the eruption cycle could go on for a while. Or it could abruptly shut off and be done tomorrow."
CRITICAL THINKING QUESTION
Volcanic ash poses a hazard to jet engines. What other hazards does it create?
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