This image provided by the Alaska Volcano Observatory shows the summit of Spur Mountain in Alaska on October 24, 2024. Credit: Wyatt Mayo/Alaska Volcano Observatory, U.S. Geological Survey (via AP)
Geologists are noticing an increase in the number of earthquakes occurring beneath a volcano near Alaska’s largest city this year.
Spur Mountain, about 80 miles (129 kilometers) northwest of Anchorage, last erupted in 1992, spewing a cloud of ash nearly 12 miles (19 kilometers) into the sky and prompting flight cancellations and people wearing masks. . Another eruption at the 11,100-foot (3,383-meter) stratovolcano could cause significant disruption to the city, according to the Alaska Volcano Observatory.
The observatory raised Spur Mountain’s alert status from green to yellow in October, when a noticeable increase in seismic activity and satellite data showed ground deformation. Observatory scientist David Fee said Friday that about 1,500 small earthquakes have occurred beneath the volcano this year, compared to about 100 in a normal year.
While it may seem like a lot, “it’s not a huge amount,” Fee said. It may or may not be a precursor to an eruption. Similar earthquake tremors occurred from 2004 to 2006, but since then the area has subsided without any eruptions.
“We don’t see any major changes in the data that would indicate that an eruption is imminent,” Fee said. “We’ve had this low level of anxiety for some time now and of course we’re monitoring very closely to detect any changes and what that means.”
A small plane flies toward Merrill Field on October 2, 1992, with plumes of volcanic ash and steam from Mount Spur dominating the Anchorage, Alaska, skyline. Credit: Paul Souders/Anchorage Daily News via AP
Scientists are monitoring seismic observatories, global satellite data and webcams for further changes that could signal an impending eruption. As magma approaches the surface, it can increase earthquakes, ground deformation, and the occurrence of summit lakes and fumaroles (vents that open into the earth’s surface to release gas and steam).
The volcano last erupted in 1992, when it erupted from a side crater on Crater Peak, about 3 kilometers (2 miles) south of the summit. That year’s eruption dumped about a quarter-inch of ash on Anchorage, forced residents to stay indoors or wear masks, and sent clouds as far as Greenland.
A similar eruption occurred from the same crater in 1953. The last known eruption from the summit was more than 5,000 years ago.
Volcanic ash is angular and sharp and has been used as an industrial abrasive. Powdered rock can cause jet engines to stall, and a 1992 eruption closed Anchorage and nearby airports.
Closing an airport is always an inconvenience in a state with few roads, but it’s more than just an inconvenience. Business will also be affected, primarily because of Alaska’s proximity to Asia, which makes Anchorage Airport one of the world’s busiest cargo hubs along with Memphis, Hong Kong and Shanghai.
Located in a ring of volcanoes, Mount Spur is one of 53 volcanoes in Alaska that have been active over the past 250 years.
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