Seven months after an earthquake swarm beneath Mt. Edgecumbe led volcanologists to determine that the Sitka-area volcano is active, data collection and research are continuing.
Since August 2018, magma has risen beneath the formerly dormant volcano and caused almost 3 inches of deformation annually, University of Alaska Fairbanks associate professor of geodesy Ronni Grapenthin said.
An eruption is not imminent, he added.
Since April’s quakes, seismic activity on the mountain has subsided, he noted, but the mountain is deforming more quickly than any other Alaska volcano. Mt. Edgecumbe, or L’ux Shaa in Tlingit, is located about 15 miles west of Sitka.
“It’s a lot (of ground deformation) compared to other Alaska volcanoes. … We’ve had other volcanoes with similar pulses of deformation as Edgecumbe in the past, but those usually have been kind of short-lived, not going on for that long. So it is, right now, the fastest deforming volcano in Alaska,” Grapenthin said in a phone interview.
In May, a team of scientists from the Alaska Volcano Observatory installed GPS and seismic sensors on the mountain in order to gather more detailed information.
Since activity began, magma has risen from about 12 miles beneath the surface to 6 miles, he said. For the time being, the professor sees no signs that shallower magmatic activity is taking place.
Before any eruption, he said, certain warning signs would be observable.
“For a volcano like Edgecumbe that hasn’t erupted in a long time, at least hundreds of years, we wouldn’t expect that there’s an established path to the surface,” he said. “You would experience a lot of breaking of rock — the magma would have to break a lot of rock to make its way to the surface. And we’d see that especially now, with instrumentation on the volcano.”
Grapenthin characterized the current seismic activity beneath Kruzof Island as “background.”
“There was that swarm in April and that swarm subsided. So right now, it’s certainly back to what one might consider background. … The April activity has basically subsided, it was a few days of swarm, a lot of stress was released and that has gone down again,” he said.
For now, Sitka’s local volcano will remain under observation, though Grapenthin stressed that he sees no signs of imminent eruption. The next steps involve installing additional sensors and gathering data.
“There are plans to expand the ground-based network to be able to add additional seismometers and ground motion sensors, et cetera. And then in terms of the science now, hopefully, we can try to do more detailed modeling of these observations that we have now,” he said.
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