By GARLAND KENNEDY
Sentinel Staff Writer
Ground deformation beneath the Mt. Edgecumbe volcano continued in 2023, but no eruption is imminent, a team of experts said at a public meeting Monday night.
But the experts, volcanologists from the Alaska Volcano Observatory, said they plan additional research this summer around the Kruzof Island landmark.
Activity beneath the volcanic cone came to the observatory’s attention in April 2022 after an earthquake “swarm” was detected there. Follow-up analysis of satellite data showed the mountain deforming at a rate of 8.7 centimeters annually, the observatory reported last spring on the U.S. Geological Survey website.
Since then, the AVO has updated the figure to about 10.4 cm of yearly deformation, volcanologist Cheryl Cameron told the Sentinel this week. Long classified as “dormant,” Mt. Edgecumbe is now officially classified as an active volcano because of the subterranean activity.
Cameron, who is based in Fairbanks, spoke to the Sentinel during her visit to Sitka.
“The overarching message is that we don’t see any sign of that magma currently coming any closer to the surface,” Cameron said. “But if we did, if it was leading toward eruption, we’d see lots more earthquakes. It’s actually been pretty seismically quiet in the last year. We would see heat and we would see gas changes from satellite sensors in space. We would see a change in that deformation rate, we think we would have months to weeks of heightened activity prior to any eruption.”
Formed in 1988, the observatory operates with state and federal agencies including the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the State of Alaska Division of Geological and Geophysical Surveys. Cameron works for the State of Alaska under the Department of Natural Resources. She was in town with another volcanologist, Kristi Wallace, who works for the U.S. Geological Survey.
After last year’s flurry of activity, AVO installed a seismometer on the mountain to monitor activity more closely, and plans to return to town in July to place additional sensory equipment, although permits from the U.S. Forest Service are pending.
“We have only one ground-based monitoring session on Edgecumbe,” Cameron said. “The type of earthquakes that we’re looking for are associated with magma and fluid movement; they’re really tiny. They’re not like tectonic quakes… We want to precisely locate those in 3-D space under the Earth’s crust. And so to do that, we generally to have at least four seismometers on a volcano.”
In this summer’s project the team plans to put in three more stations. “So we would surround Mt. Edgecumbe proper, because that’s where our modeling is showing that the intrusion is happening,” Cameron said.
And even though magma has risen, it’s still many kilometers deep, she noted.
“Lots of magmatic intrusions never make it to the surface, although some do,” she said.
Under clear skies, Cameron spoke with the Sentinel on a walk through Sitka National Historical Park Tuesday, with Mt. Edgecumbe the landmark defining the western horizon.
Cameron said Monday’s public forum was well attended.
“One of the great things about this kind of community involvement work is Sitkans are really engaged and involved and they’re very knowledgeable and thoughtful.”
Some of the 100 Sitkans attending Monday’s public presentation asked about local tectonics, hot springs, and an image that showed up on a boat’s fishfinder in Nakwasina Sound in December 2022 that showed what appeared to be a miniature volcano erupting on the seafloor.
Cameron said the location of the Nakswasina phenomenon “is way outside of the Mt. Edgecumbe volcanic field, not a volcano. We knew that right away.”
“We were like, well, what is it? And we thought, maybe a mud volcano. But the more we poked into it, the more it just seems like it’s a reflection of the difference between, perhaps, temperature or salinity associated with a tide change… We knew right away it wasn’t related to volcanic magma. It’s just too far north and east,” she said.
Even though the strange sighting wasn’t volcanic, Cameron was glad the observers reached out to AVO to report it.
“I would rather be contacted 100 times with things that turn out not to be really the volcano, than to miss something,” she said.
Observations can be reported to the volcano center through the website https://avo.alaska.edu/contact.php.
Community interest and communication are important, as the observatory can’t keep track of everything on its own, Cameron said.
“There’s been a lot of interest, which is really understandable,” she said. “But also we encourage people in the community, if they see something unusual, to contact us with their observations. Quite a number of people have done so, which we really appreciate because we are here at AVO, we’re not here in Sitka, we can’t see it every day. We don’t get to go to Kruzof on a regular basis. And so we’re really dependent on community observations, as well as our geophysical instrumentation.”
