Last week, [2-23-26], a team of specialists from the Alaska Volcano Observatory stopped by Sitka to do some station maintenance work on Mt. Edgecumbe, a volcano on nearby Kruzof Island.
Ellie Boyce is a field engineer with the AVO. She and a coworker were joined by four technical team members from the U.S. Geological Survey in Anchorage to repair two of four stations surrounding the historically active volcano.
“We had a failed component in the GPS system, so we needed to go out and replace the antenna that received the signals from the satellites, and that’s a pretty straightforward fix,” says Boyce. “It only took us one day.”
The GPS system in question involves four metal tripods stationed around Mt. Edgecumbe since 2023. The system provides data in real time about tectonic shifts happening at the volcano, rather than waiting for a satellite to pass overhead, which happens only once every 12 days and produces less accurate results when it’s snowing.
“And so we’re really interested in whether two stations on opposite sides of the volcano may be moving toward each other and down, which would suggest deflation of a magma body, or if they’re possibly moving away from each other and up, that would suggest there could be inflation of a magma chamber,” says Boyce.
Boyce says deflation generally suggests that a volcano is less likely to erupt in the near future, whereas inflation refers to a recharge of a magma reservoir that could feed a future eruption.
While there are no written observations of it erupting, Tlingit oral history describes small eruptions around 800 years ago, and geologic evidence points to a major eruption around 13,000 years ago. The status of the 3,202-foot volcano located 16 miles from Sitka was changed from “dormant” to “historically active” in 2022 following a swarm of small earthquakes.
Since then, Boyce says the AVO has installed local seismometers alongside the antennas, which are able to provide more accurate information.
“So we have local seismometers that we can use to more precisely locate where earthquakes are happening at what depth, and if they’re sort of centering on a location under the volcano versus perhaps out towards a fault or something that may be more tectonic in origin,” says Boyce.
Ronni Grapenthin is a professor who works at the Geophysical Institute at the University of Alaska Fairbanks. He says that since mid-2024, the AVO has been observing deflation of Mt. Edgecumbe, and labeled it a color code GREEN, meaning it’s in a “typical background, noneruptive state,” since the GPS-system was first installed.
Two antennas at the site began to fail back in December. Boyce says it wasn’t until February that the AVO team found a good weather window to swing by and fix them. She says her team is planning more field work this summer to keep the equipment monitoring smoothly.
