Scientists monitoring Alaska volcano after rise in earthquakes beneath it

Mount Spurr last erupted in 1992, blowing a nearly 12-mile (19km) ash cloud into the air, cancelling flights and forcing people in Anchorage to wear masks.

Another eruption at the 11,100ft (3,383m) stratovolcano could severely disrupt the city, which sits around 80 miles (129km) away, according to the Alaska Volcano Observatory.

The observatory raised its alert status for Mount Spurr from green to yellow in October, when the increase in seismic activity became more pronounced and scientists spotted ground deformation in satellite data.

There have been around 1,500 small earthquakes underneath the volcano so far this year compared with about 100 in a normal year, according to observatory scientist David Fee.

Although that may seem a lot it's "not an enormous 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 don't see any significant change in our data that would tell us that an eruption is imminent," Mr Fee said.

"Things have been kind of this low-level unrest for a while now and we're, of course, watching it very closely to detect any changes and what that might mean."

Through monitoring seismic stations, global satellite data and a webcam, geologists are looking for additional changes that would signal an impending eruption.

Magma moving closer to the surface would result in an increase in earthquakes, ground deformations, and the creation of a summit lake or fumaroles - vents that open in the surface to vent gas and vapours.

When the volcano last erupted around 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 in the last 250 years.

-SKY NEWS