Geologists are monitoring a volcano near Alaska’s largest city after an increase in earthquakes beneath it could signal an impending eruption.
Mount Spurr last erupted in 1992, blowing an ash cloud nearly 12 miles into the air, canceling flights and forcing Anchorage residents to wear masks.
Another eruption of the 3,383 m high stratovolcano could seriously disrupt the town, located about 129 km away, according to the Alaska Volcano Observatory.
The observatory raised its alert status for Mount Spurr from green to yellow in October, when increased seismic activity became more pronounced and scientists spotted ground deformation in satellite data.
There have been about 1,500 small earthquakes beneath the volcano so far this year, compared to about 100 in a normal year, according to observatory scientist David Fee.
While that may seem like a lot, it’s “not a huge amount,” he said.
It may or may not be a precursor to an eruption – similar seismic unrest occurred from 2004 to 2006, but subsided without an eruption.
“We’re not seeing any significant changes in our data that would indicate to us that an eruption is imminent,” Fee said.
“Things have remained low intensity for some time now and we are, of course, monitoring them very closely for any changes and what that might mean.”
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Geologists warn of changes signaling imminent eruption
Using monitoring of seismic stations, global satellite data and a webcam, geologists look for additional changes that would signal an impending eruption.
Bringing magma closer to the surface would lead to increased earthquakes, ground deformation and the creation of a summit lake or fumaroles – vents that open at the surface to vent gases and vapors.
When the volcano last erupted, about a quarter of an inch of ash fell on Anchorage that year.
Mount Spurr is located on the volcanic Ring of Fire. It is one of 53 volcanoes in Alaska that have been active over the past 250 years.