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Unusual activity at Alaska volcano prompts extra look at remote peak
- Alaska Beacon
- 10 hours ago
- 3 min read
Alaska Volcano Observatory increases alert level at Kupreanof on the Alaska Peninsula
By James Brooks
Alaska Beacon
The Alaska Volcano Observatory has raised the caution level at Kupreanof Volcano on the Alaska Peninsula, a normally quiet peak that hasn’t had a major eruption in almost 570,000 years.
“It’s a typical Alaska volcano. It’s not dormant by any means,” said Matt Haney, the U.S. Geological Survey Scientist-in-Charge at the observatory.
On Tuesday, the observatory issued an advisory notice saying that it had detected a rising number of earthquakes and sulfur dioxide emissions at the peak.
“This activity is likely caused by a magmatic intrusion beneath the volcano,” the observatory said in the notice.
“It’s been a classic volcanic unrest sequence … From the science point of view, it’s been very fascinating to see unrest develop at Kupreanof,” Haney said.
Rising unrest does not mean an eruption will happen or is even likely to happen. Last summer, Mount Spurr near Anchorage showed a rising level of activity that appeared to indicate a likely eruption. Despite those signs, no eruption took place and seismic activity has since declined.
A 6,217-foot peak, Kupreanof is in a particularly remote part of the Alaska Peninsula National Wildlife Refuge, 505 miles southwest of Anchorage. The closest permanently inhabited community is Perryville, 26 miles to the southeast.
Though isolated, Kupreanof — like most of Alaska’s volcanoes — is near trans-Pacific flight routes, and a sufficiently large eruption could disrupt cargo and passenger flights between North American airports and Asia.
Haney said by phone on Thursday that the observatory detected an escalating string of earthquakes beneath the volcano starting in February and continuing through this week.
On Wednesday, instruments recorded the largest earthquake yet, measured variously at Magnitude 3.5 and 3.0.
Satellites have also measured rising concentrations of sulfur dioxide near Kupreanof. That gas is a standard sign of magma moving near the surface of the Earth.
“It’s not just one of our monitoring data streams that’s showing (activity) above our background levels. Now it’s seismicity and gas. When we have two of our data streams, that’s really making the diagnosis with higher confidence that there has been a magma intrusion beneath Kupreanof,” Haney said.
There are no historic records of a confirmed eruption at Kupreanof. In 2015, a mariner reported “black smoke northwest of Ivanof Bay,” likely from Kupreanof, and in 1987, a pilot reported what may have been a small eruption.
“Although reports from Kupreanof are uncommon, steaming from Kupreanof has been noted for at least the last 75 years,” the observatory notes in its description of the 2015 report.
The last confirmed eruption was about 570,000 years ago.
As a result, the volcano has no permanent monitoring network.
Hannah Dietterich, a research geophysicist at the observatory, said on Wednesday that she and others at the observatory have begun arranging more regular satellite measurements, including with instruments designed to measure whether the ground around the volcano is bulging upward.
Satellite images taken this week show Kupreanof still covered in a thick layer of ice and snow, indicating that the peak has not warmed to the point of melting that accumulation.
Haney said that in addition to satellite measurements, the observatory may use a helicopter to take a “quick-deploy” monitoring station to the volcano in July, during a previously scheduled trip to another nearby peak.
• James Brooks Cascade is a longtime Alaska reporter who lives in Juneau. He previously worked at the Anchorage Daily News, Juneau Empire, Kodiak Mirror and Fairbanks Daily News-Miner. Alaska Beacon is part of States Newsroom, the nation’s largest state-focused nonprofit news organization.
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