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Eruption risk level down for Aleutian volcanoes

Tanaga in November 2012.
Roger Clifford
Alaska Volcano Observatory/U.S. Geological Survey
Tanaga in November 2012.

Scientists last week warned that two Aleutian volcanoes were at a heightened risk to erupt following a series of high-intensity earthquakes nearby.

Since then, they’ve lowered the risk levels on Tanaga and Takawangha. But they’re continuing to watch for any signs the volcanoes could still erupt in the future.

John Lyons is a research geophysicist with the Alaska Volcano Observatory, which studies volcanoes like the ones on Tanaga Island and watches out for potential hazards. They keep an eye on the volcanoes on the island with satellites and six remote monitoring sites.

“We had seen seismic unrest going back into the fall of 2022 at Takawangha Volcano,” Lyons said.

Swarms of earthquakes, like the one at Takawangha, can be precursors to volcanic eruptions.

Two weeks ago, Lyons said the unrest started underneath its neighbor, at the Tanaga Volcano.

“At the same time, the earthquakes got shallower — they moved up toward the surface,” he said.

That’s when the observatory upped the risk, to color-code orange — which means a volcano is showing signs of unrest with an increased potential to erupt. Activity peaked between March 9 and 11.

But Lyons said after that, the rate, intensity and magnitude of the earthquakes happening there all began to drop — plus, observers weren’t noticing other signs of volcanic activity, like steaming.

“This was last Thursday,” he said. “At that point, we felt pretty good lowering the color code from orange to yellow."

That means the observatory is seeing signs of unrest of the volcano, but doesn’t think those signs are going to lead to what Lyons calls “imminent eruptive activity.”

“Yellow is like an advisory level,” Lyons said. “It’s kind of like, heads up, this isn’t background activity — there are still earthquakes ongoing. I think in the last week, we’ve had maybe 15 or so magnitude 2-plus earthquakes, which are pretty big for volcanoes.”

Still, he said those are a step down from the magnitude 3-plus earthquakes the observatory was picking up earlier in the month.

Lyons said his office is continuing to keep an eye on activities at Tanaga and Takawanga and that they’ll be ready to raise the alert level again, if needed. (You can find daily updates on the volcanoes here.) Lyons said there isn’t much of a concern about the human impacts of the volcanoes, since Tanaga Island is uninhabited and the closest community to the volcanoes is Adak, 60 miles away.

The volcanoes the observatory monitors in Cook Inlet are closer to the Kenai Peninsula.

Lyons said Sunday’s earthquake, near Homer, wasn’t close enough or large enough to raise concerns about impacting any volcanoes across the inlet.

“It’s just the result of living in a very tectonically active area,” he said. “We get these energetic earthquakes quite frequently.”

That’s not to say Kenai Peninsula residents are immune from experiencing eruptions a little closer to home. Tomorrow marks 14 years to the day since Mount Redoubt’s last eruption — on March 22, 2009.

Sabine Poux is a producer and reporter for the Brave Little State podcast of Vermont Public. She was formerly news director and evening news host at KDLL in Kenai.

Originally from New York, Sabine has lived and reported in Argentina and Vermont and Kenai.
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