Magma beneath the long-dormant volcano was observed to be moving upwards
Research reveals magma activity beneath Mt Edgecumbe.
Magma beneath the long-dormant Mount Edgecumbe volcano in southeast Alaska is moving upward through the Earth’s crust, according to a recent study from the Alaska Volcano Observatory.
An innovative observatory method may enable early identification of volcanic activity in Alaska. According to computer modeling based on satellite data, magma at Mount Edgecumbe rises from a depth of approximately 12 miles to about 6 miles, causing significant surface deformation and earthquakes.
“That’s the fastest rate of volcanic deformation that we have in Alaska right now,” said the study’s lead author, Ronni Grapenthin, an associate professor of geodesy at the University of Alaska in Fairbanks. “While it is not unusual for volcanoes to deform, the activity at Edgecumbe is unusual because the reactivation of dormant volcanic systems is rarely seen,” he said.
According to Grapenthin, an eruption is not imminent. Researchers from the UAF Institute of Geophysics and the US Geological Survey recently published their findings in a journal Geophysical Research Letters.
The Alaska Volcano Observatory collaborated with another Geophysical Institute unit, the Alaska Satellite Facility, to analyze cloud data—a first for the volcano team. Instead of downloading and organizing data, which can take weeks or months, researchers can use cloud computing, which uses remote servers to store data and provide computing services.
When a series of earthquakes were detected near Mount Edgecumbe on April 11, 2022, the research team got to work. The researchers analyzed ground deformation detected in satellite radar data over the past 7 1/2 years.
Four days later, on April 15, the team had a preliminary result: the intrusion of new magma had caused earthquakes. A small number of earthquakes began under Edgecumbe in 2020, but the cause was ambiguous until strain results were obtained.
Additional data processing confirmed the preliminary finding. The Alaska Volcano Observatory notified the public on April 22, less than two weeks after the latest series of Edgecumbe earthquakes were reported.
“We’ve done this kind of analysis before, but new streamlined cloud-based workflows have cut weeks or months of analysis down to just days,” said David Fee, coordinating scientist at the Geophysical Institute’s Alaska Volcano Observatory.
Mount Edgecumbe, at 3,200 feet, is on Krusoff Island on the west side of Sitka Sound. It is part of the Mount Edgecumbe volcanic field, which includes the domes and crater of the adjacent Crater Ridge. Most impressive to the researchers was an area of uplift on southern Krusof Island, 16.5 miles in diameter, centered 1.5 miles east of the volcano. The upward deformation began abruptly in August 2018 and continued at a rate of 3.4 inches per year, totaling 10.6 inches by early 2022.
Subsequent computer modeling showed that the cause was the intrusion of new magma. The new strain-based analysis will allow for earlier detection of volcanic unrest as soil deformation is one of its earliest indicators. Deformation can occur without accompanying seismic activity, making ground uplift a key symptom to monitor.
The volcano observatory is applying the new approach to other volcanoes in Alaska, including Trident Volcano, about 30 miles north of Katmai Bay. The volcano shows signs of heightened unrest. Mount Edgecumbe shows no signs of an imminent eruption, Grapenthin said.
“This magma intrusion has been going on for three years and more,” he said. “Before an eruption, we expect more signs of unrest: more seismicity, more deformation, and — most importantly — changes in the patterns of seismicity and deformation.”
The researchers say the magma probably reaches the upper chamber through a nearly vertical conduit. But they also believe that the dense magma already in the upper chamber is prevented from moving further up.
Instead, new magma lifts the entire surface. Mount Edgecumbe is 25 miles west of Sitka, which has a population of about 8,500. The volcano last erupted 800 to 900 years ago, according to an oral history of the Lingit transmitted by Herman Kitka. A party of Tlingit in four canoes camped on the shore about 15 or 20 miles south of some large plumes of smoke, according to the report. A scouting party in a canoe was sent out to investigate the smoke and reported, “the mountain flickers, fire and smoke.”
Reference: “Return from Dormancy: Rapid Inflation and Seismic Unrest Induced by Transcrustal Magma Transfer at Mt. Edgecumbe (L’ux Shaa) Volcano, Alaska” by Ronni Grapenthin, Yitian Cheng, Mario Angarita, Darren Tan, Franz J. Meyer, David Fee and Aaron Wech, October 10, Geophysical Research Letters.
The Alaska Volcano Observatory is a joint program of the Geophysical Institute, the US Geological Survey, and the Alaska Division of Geological and Geophysical Survey.
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