Daily Sitka Sentinel

Volcanologists: Edgecumbe Not Set to Erupt

By GARLAND KENNEDY
Sentinel Staff Writer

Following a flurry of seismic activity beneath the Sitka landmark peak Mt. Edgecumbe last month, a team of volcanologists has determined that the volcano is now active, but doesn’t pose an immediate threat of eruption.

Two scientists from the Anchorage-based Alaska Volcano Observatory flew to Sitka last week as a first step toward installing seismic and GPS sensors on the mountain and hosted a number of public events to present their findings to Sitkans.

What the Anchorage and Fairbanks experts termed a “swarm” of small earthquakes beneath the mountain was detected in April. Subsequent investigation by AVO determined that ground deformation has occurred near the volcano over the last four years – a sign of magma moving beneath the surface, AVO’s website says.

If the mountain was progressing toward an eruption there would be much more warning, AVO scientist Cheryl Cameron said Wednesday.

“We do expect if it was going to erupt, there would be a lot more precursory activity. There would be warnings,” Cameron said Wednesday. Apart from volcanoes, she noted, there are other natural disasters that Sitkans should be prepared to deal with: landslides, earthquakes, and tsunamis.

“So everyone should have an emergency kit with spare food and water,” she said.

Cameron spoke with the Sentinel at the BackDoor Cafe, where she had set aside time to speak with anyone from the public with questions about Mt. Edgecumbe.

AVO describes a volcano as “active” for a number of reasons, including seismic swarms, ground deformation that indicates magmatic intrusion, an actual eruption, or a suspected eruption.

The first two occurrences have been observed around Mt. Edgecumbe.

While this week’s poor weather prevented the volcanologists from spending time on Kruzof Island where Mt. Edgecumbe is located, AVO scientist-in-charge Michelle Coombs said her team plans to install a seismic monitoring apparatus on the island soon.

“If things go as planned, we hope to start the local monitoring on Kruzof with a single station that we might put out as soon as a couple of weeks, weather, logistics and everything permitting,” Coombs said.

If possible, she’d like to see a more extensive system installed on the mountain this summer.

So far, instruments have been installed on 34 volcanoes in Alaska, Coombs said. In the state, 54 volcanoes are considered active.

“Alaska has a lot of volcanoes,” Coombs said. “Three of them are erupting right now. Eruptions can range from pretty small to much larger, the larger ones happen a lot less frequently… Unlike earthquakes, for example, which happen out of the blue, volcanoes give a fair bit of warning usually, especially volcanoes like Edgecumbe that have not erupted in a while. That’s why we put in additional monitoring instruments.”

Earth satellites have detected 10.6 inches of ground deformation around the volcano since 2018, AVO’s website says.

AVO geophysicist Ronnie Grapenthin spoke about that finding in an online event Tuesday.

“Now that certainly got our attention,” Grapenthin said. “When I first saw that I was very surprised to see that because it’s what we consider significant deformation. That’s more than we see at most of the Alaskan volcanoes.”

He added:

“The take home message is that we do expect more earthquakes, heat, gas and changing deformation before any eruption. It certainly got our attention and so we need to keep better tabs on what’s going on and having just a closer seismometer is going to help us.”

Further analysis, he added, showed that the magma causing the deformation is still far beneath the surface, about three to five miles deep.

The volcano that defines Sitka’s western horizon is about 600,000 years old, Cameron said, and has erupted a number of times through the millenia.

“A lot of eruptions from a lot of different events formed those cone shapes that we see,” Cameron said. “And then, about 14,000 - 13,000 years ago there was a series of eruptions, some of them larger, we think related to regional ice unloading, which decreased the pressure on Edgecumbe that allowed magma to come up. That produced the three feet of ash that you see underneath everything in Sitka.”

The Tlingit name for the volcano is L’ux, which translates to English as Blink.

“One of the things that people can do now is something that everybody should have anyway because we live in an area with other natural hazards like landslides and earthquakes and possible tsunamis,” Cameron said. “And so that’s to build an emergency kit, to actually have your food, your water, some medications… Include N95 masks (to deal with ashfall), which we all now have, thanks to the pandemic.”

Volcanoes that erupt near airline routes, as they do in Southcentral Alaska, disrupt air traffic, Coombs noted.

“Most of our volcanoes are pretty remote, but they’re right underneath the North Pacific air routes,” she said. “So there are estimates that upwards of 50,000 people a day traverse those air routes over Alaskan volcanoes... that’s kind of our primary hazard, honestly, and there are a couple of volcanoes on average that erupt every year in the state and a lot of them erupt explosively, putting ash up in the air. So we work really closely with the FAA and the weather service.”

Coombs said she doesn’t think Mt. Edgecumbe is anywhere near an eruption.

“But just a little bit of peace of mind, perhaps,” she said. “People in Alaska have dealt with ash-producing eruptions before and we can again in the future.”