Research reveals magma activity under Mount Edgecumbe.
According to a recent study from the Alaska Volcano Observatory, magma under the long-dormant Mount Edgecombe volcano in southeast Alaska is moving upward through the Earth’s crust.
Innovative observatory method may allow early identification of volcanic activity in Alaska. According to computer modeling based on satellite data, magma at Mount Edgecumbe rises from about 12 miles deep to about 6 miles deep, causing significant surface deformation and earthquakes.
“This is the fastest rate of volcanic deformation we’re currently experiencing in Alaska,” said the paper’s lead author, Ronnie Grabenthen, professor of geodesy at the University of Alaska Fairbanks. “And while it is not uncommon for volcanoes to deform, the activity at Edgecumbe is unusual because reactivation of dormant volcanic systems is rarely observed,” he said.
According to Grabenthen, the eruption is not imminent. Researchers from the UAF Institute of Geophysics and the US Geological Survey recently published their findings in the journal Geophysical Research Letters.
The Alaska Volcano Observatory teamed up with another unit of the Geophysical Institute, the Alaska Satellite Facility, to analyze the data in the cloud — a first for the volcano team. Instead of having to download and organize 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 set to work. The researchers analyzed ground deformation detected in satellite radar data over the past seven and a half years.
Four days later, on April 15, the team came to a preliminary conclusion: The intrusion of fresh magma was causing the earthquakes. A few earthquakes started under Edgecumbe in 2020, but the cause was a mystery until deformation results.
Additional data processing confirmed the preliminary findings. The Alaska Volcano Observatory notified the public on April 22, less than two weeks after the latest batch of Edgecomb earthquakes were reported.
“We’ve done these types of analyzes before, but new, streamlined cloud-based workflows have reduced weeks or months of analysis to just days,” said David Fee, Alaska Volcano Observatory coordinating scientist at the Geophysical Institute.
Mount Edgecumbe, at 3,200 feet, on Kreuzov Island on the western side of Sitka Sound. It is part of the Mount Edgecumbe Volcanic Field, which includes domes and the adjacent Crater Ridge crater. What surprised the researchers most was the area of land rise on southern Kreuzov Island, 10.5 miles in diameter and centered 1.5 miles east of the volcano. The upward deformation began suddenly in August 2018 and continued at a rate of 3.4 inches per year, for a total of 10.6 inches through early 2022.
Subsequent computer modeling indicated that the cause was the intrusion of fresh magma. The new deformation-based analysis will allow early detection of volcanic disturbances because ground deformation is one of its early indicators. Deformation can occur without accompanying seismic activity, making ground uplift a major symptom to watch for.
The Volcano Observatory is applying the new approach to other Alaskan volcanoes, including Trident Volcano, about 30 miles north of Katmai Bay. The volcano shows signs of mounting unrest. Grapenthin said Mount Edgecumbe is showing no signs of an imminent eruption.
“This magma intrusion has been going on for more than three years,” he said. “Before a volcano erupts, we expect more signs of unrest: more earthquakes, more deformation, and most importantly – changes in earthquake and deformation patterns.”
The researchers say the magma likely reached the upper chamber through a near-vertical channel. But they also believe that magma is preventing it from moving upward because of the thick magma already in the upper chamber.
The new magma is pushing the entire surface up instead. Mount Edgecumbe is located 15 miles west of Sitka, which has a population of about 8,500. The volcano last erupted 800 to 900 years ago, as reported in the Lingit oral history transmitted by Hermann Kitka. A group of Tlingits in four canoes had camped on the coast about 15 or 20 miles south of some large plumes of smoke, according to the account. A scouting party was sent out in a canoe to investigate the smoke and reported: “Jebel Yarmesh, breathing fire and smoke.”
Reference: “Return from Dormancy: Rapid Inflation and Seismic Turbulence Caused by Transformation of Transcrustal Magma at Mt. Edgecombe Volcano (Lox Sha), Alaska” by Ronnie Grabenthen, Whitian Cheng, Mario Angarita, Darren Tan, Franz G. Meyer, David V., Aaron Which, Oct. 10, Geophysical Research Letters.
The Alaska Volcano Observatory is a joint program of the Geophysical Institute, the US Geological Survey, and the Alaska Department of Geological and Geophysical Surveys.
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