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AVO Lowers Bogoslof Volcano Aviation Alert

T. Keith, U.S. Geological Survey

A volcano in the eastern Aleutianserupted suddenly Tuesday afternoon prompting the Alaska Volcano Observatory (AVO) to issue its highest alert level for aviation. The alert has since been downgraded.

Bogoslof volcano is on an uninhabited island 60 miles northwest of Unalaska.

AVO scientist Michelle Coombs says several pilots reported seeing an ash cloud about 34,000 ft -- nearly the height of a commercial jet -- above Bogoslof.

She says satellite data show a short-lived explosion occurred around 4pm, but the activity has since died down.

Coombs says the volcano seems to have erupted because it was “gassy."

“It looked like it had a lot of gas in it -- a lot of sulfur gas and probably water gas," Coombs said. "[The eruption] might have been the opening event in possible the eruptive sequence.” 

An eruptive sequence that might include new land forming.

“People have seen that the shape of the island has changed," she said. "New little side islands have grown up and then are sometimes destroyed, by explosions or wave action and erosion.”

The area is very dynamic. Coombs says over the years the shape, height and number of islands have changed. Since the 1700s, Bogoslof has erupted 8 times and Coombs says it’s hard to know how long this eruption will last.

Eruptions are like personalities.

“Some volcanoes tend to erupt have a big explosive eruption and then go back to sleep," she said. "A lot of volcanos have more longer-lasting, low-level activity.”

She says long eruptions -- lasting weeks or months -- are common in Alaska.

Because there is no-ground based monitoring equipment on Bogoslof volcano, the AVO cannot predict future eruptive activity. Instead, they are monitoring from afar -- using satellite images and other data for indications of significant seismic activity.

If this eruption continues it could impact aviators, mariners and drop ash on nearby communities.

Prior to this, the last recorded eruption of Bogoslof was in 1992 and lasted nearly a month.

Zoë Sobel reported for KUCB from 2016 until 2019. She returned to KUCB after a year living in Nepal and Malaysia as a Luce Scholar. She then returned to KUCB as a ProPublica reporter August of 2020 through August of 2021.
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