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Five Aleutian volcanoes show signs of unrest

East flank of Takawangha on June 10, 2021.
Loewen, M. W.
Alaska Volcano Observatory / U.S. Geological Survey
East flank of Takawangha on June 10, 2021.

Four Aleutian volcanoes have been under elevated alert levels for about a year — and now, they’re joined by a fifth.

The new one is the ice-filled caldera of Takawangha, which rises 4,753 feet out of the Bering Sea in the far western Aleutians.

Researchers put the volcano on the watch list when a swarm of earthquakes with magnitudes between two and three began increasing around Takawangha.

When an earthquake is caused by tectonic plate shifts, it typically results in a major earthquake that is followed by smaller and smaller aftershocks that taper out.

But in a swarm, there can be a significant increase in the rate, and often the magnitude, of earthquakes.

John Lyons, a research geophysicist at AVO, said swarms often point to volcanic activity.

“That typically indicates that there's been magma or volcanic fluid there,” Lyons said. “A swarm of earthquakes can often precede activity at the surface, including an eruption.”

The swarm began Nov. 18, prompting the Alaska Volcano Observatory to move the volcano’s Aviation Color Code to ‘Yellow.'

All five of the volcanoes are concentrated along the Aleutian Chain. Most of them have been fluttering in and out of ‘Yellow’ and ‘Orange’ advisory levels, which ranges from elevating unrest, to minimal eruptions.

While five volcanoes rumbling at the same time might sound like a lot, Lyons said it’s not uncommon for the state.

“Because there's so many active volcanoes in Alaska, having five that have an elevated color code isn't really extraordinary,” Lyons said.

Takawangha is about 55 miles west of Adak, and would threaten the city of around 200 people should it erupt. But Lyons said the current advisory level is no cause for concern.

“The potential hazard to people in Adak is very low right now. And because the volcano is so well monitored, and because the Alaska Volcano Observatory is keeping an eye on it, there will be signs and we will catch those signs and put out timely notices if there's any change in activity,” he said.

As of Monday, the swarm was still continuing at Takawangha and the color code remained at ‘Yellow.’

Theo Greenly reports from the Aleutians as a Report for America corps member. He got his start in public radio at KCRW in Santa Monica, California, and has produced radio stories and podcasts for stations around the country.
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