Swarm of earthquakes under Mount Edgecumbe volcano doesn’t necessarily indicate volcanic activity, experts say

ANCHORAGE, Alaska (KTUU) - For about a week, a series of hundreds of earthquakes have been occurring near Mount Edgecumbe, the dormant volcano located across Sitka Sound from the city of Sitka along the Southeast Alaska panhandle.

Scientists have not yet determined if the continuing seismic activity is an indication of impending volcanic activity. Alaska Volcano Observatory Research Geophysicist David Schneider said the activity started on April 11, and that all of the quakes have been minor thus far.

“There have been two earthquakes that have been in excess of magnitude two and hundreds of smaller ones that have been located at this point,” Schneider said.

He said the seismic activity is declining, but still present.

“These earthquakes are unusual in the history of Edgecumbe,” Schneider said. “Some retrospective analysis of seismic data shows that there has been a slight uptick in earthquake activity beginning about 2020.”

Schneider also said that the quakes don’t necessarily mean there is volcanic activity.

“The fact that these are under the volcano, I mean it’s likely that they are related to volcanic activity of some sort,” Schneider said. “That said, many volcanoes have seismic swarms and it does not necessarily lead to an eruption.”

Geologic records show the last deposits from Mount Edgecumbe are about 4,500 years old, but Schneider says that Tlingit history mentions minor volcanic activity about 800 years ago.

Edgecumbe is considered dormant, but not extinct. Schneider said that volcanoes are considered dormant if there is record of an eruption in the past 2,000 to 8,000 years. They are considered extinct if the last eruption was more than 8,000 years ago.

Schneider said scientists are in a watchful waiting period.

“This is kind of a slow burn, and it could fade away to nothing. It could also lead to an eruption,” Schneider said.

If Mount Edgecumbe does have an eruption on the way, Schneider said experts would expect to see many more signs of activity.

Schneider said people don’t need to be concerned, but people should always be prepared.

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