Research reveals magma activity beneath Mount Edgecumbe.
According to a recent study from the Alaska Volcano Observatory, magma beneath the long-dormant Mount Edgecumbe volcano in Southeast Alaska moves up through the Earth’s crust.
The observatory’s innovative method could allow early identification of volcanic activity in Alaska. According to computer models based on satellite data, magma on Mount Edgecumbe rises from a depth of about 12 miles to about 6 miles, causing significant surface deformation and earthquakes.
“That’s the highest rate of volcanic deformation we currently have in Alaska,” said the research paper’s lead author, Ronni Grarenthin, an associate professor of geodesy at the University of Alaska Fairbanks. “And while it’s 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 Grapenthin, an eruption is not imminent. Researchers from the UAF Geophysical Institute and the US Geological Survey recently published their findings in the journal Geophysical Survey Letters.
The Alaska Volcano Observatory teamed up with another Geophysical Institute unit, the Alaska Satellite Facility, to analyze 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 got to work. The researchers analyzed the 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: An intrusion of new magma caused the earthquakes. A small number of earthquakes started below Edgecumbe in 2020, but the cause was ambiguous until deformation results were produced.
Additional data processing confirmed the preliminary finding. The Alaska Volcano Observatory informed the public on April 22, less than two weeks after the last series of Edgecumbe earthquakes were reported.
“We’ve done this kind of analysis before, but new streamlined cloud-based workflows reduce weeks or months of analysis to just days,” said David Fee, the Alaska Volcano Observatory coordinating scientist at the Geophysical Institute.
Mount Edgecumbe, at 3,200 feet, is located on Kruzof 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 notable to the researchers was an area of ground elevation on southern Kruzof Island measuring 10.5 miles in diameter and centered 1.5 miles east of the volcano. The upward deformation started abruptly in August 2018 and continued at a rate of 3.4 inches per year, for a total of 10.6 inches through early 2022.
Later computer models indicated that the cause was the intrusion of new magma. The new deformation-based analysis will enable earlier detection of volcanic unrest because ground deformation is one of the earliest indicators. Deformation can occur without associated seismic activity, making ground uplift an important symptom to watch for.
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 is showing signs of heightened unrest. Mount Edgecumbe shows no signs of an imminent eruption, Grarenthin said.
“This magma invasion has been going on for more than three years now,” 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 likely reaches an upper chamber through a nearly vertical conduit. But they also believe that the magma cannot move any further up due to thick magma already in the upper chamber.
The new magma instead forces the entire surface up. 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 quoted in the Lingít oral history narrated by Herman Kitka. A party of Tlingits in four canoes had camped about 15 or 20 miles south of some large plumes of smoke on the coast, according to the report. A reconnaissance party in a canoe was sent to investigate the smoke and reported: “a mountain flashing, spewing fire and smoke.”
Reference: “Return from Dormancy: Rapid Inflation and Seismic Unrest Driven by Transcrustal Magma Transfer at Mt. Edgecumbe (L’úx Shaa) Volcano, Alaska” by Ronni Grapenthin, Yitian Cheng, Mario Angarita, Darren Tan, Franz J. Meyer, David Fee and Aaron Wech, October 10, 2022, Geophysical Survey 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 Surveys.