ANCHORAGE, Alaska (AP) – An increase in the number of earthquakes under a volcano near Alaska’s capital this year has geologists paying attention.
Mount Spurr, about 80 miles (129 kilometers) northwest of Anchorage, last erupted in 1992, sending a cloud of ash about 12 miles (19 kilometers) into the air, prompting flight cancellations and people donning masks. Another eruption of the 11,100-foot (3,383-meter) stratovolcano could seriously damage the city, according to the Alaska Volcano Observatory.
The observatory raised its alert status on Mount Spurr in October – from green to yellow – when an increase in seismic activity was detected and ground changes were detected in satellite data. Observatory scientist David Fee said on Friday there have been 1,500 small earthquakes under the volcano this year, compared to 100 in a normal year.
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While that may seem like a lot, “it’s not a lot of money,” Fee said. It can be a precursor to an explosion – or not. A similar seismic instability occurred from 2004 to 2006 before ending without an eruption.
“We’re not seeing any significant changes in our data that would tell us an explosion is imminent,” Fee said. “Things have been a little bit different for a while and we’re really watching to see what changes and what that might mean.”
Scientists are monitoring earthquake stations, global satellite data and a webcam for additional changes that may indicate an impending eruption. If the magma is getting closer to the surface, there would be an increase in earthquakes, landslides, the creation of surface seas or fumaroles, which are vents that open to the surface to release gas and steam.
The volcano last erupted in 1992 from the Crater Peak flank vent, located two kilometers (3 miles) south of the summit. The eruption dropped about a quarter-inch of ash in Anchorage that year, forcing residents to stay indoors and don masks, and the cloud drifted as far as Greenland.
A similar eruption from the same site occurred in 1953. The last known eruption from the same site was more than 5,000 years ago.
Volcanic ash is angular and sharp and has been used as an industrial abrasive. Powder rock can cause jet engines to shut down, which caused Anchorage and other nearby airports to be closed during the 1992 eruption.
Closing airports is always a problem in a country with few roads, but it can be more than just a nuisance. Business would also be affected as the Anchorage airport today ranks among the world’s busiest airports with Memphis, Hong Kong and Shanghai, largely because of Alaska’s connections to Asia.
Mount Spurr, located on the Volcanic Ring of Fire, is one of 53 volcanoes in Alaska that have been active for the past 250 years.