Scientists have upgraded the alert level at one of Alaska's most active volcanoes after increased volcanic unrest.
Starting last week, satellites detected an increase of gas emissions and elevated surface temperatures at Cleveland Volcano, which is located on an uninhabited island in the central Aleutians, west of Umnak Island.
The data indicates a potential for increased eruptions, according to Dave Schneider, a geophysicist with the Alaska Volcano Observatory, so the AVO has raised the aviation color code to "yellow" and the alert level to "advisory."
"Whether or not this results in a very benign effusion of lava in the summit crater, a short-lived explosion, or neither, remains to be seen," Schneider said.
Cleveland is frequently active, but has had a quiet period over the past nine months or so, he added.
The volcano last erupted in early June of last year, producing a small ash cloud up to 22,000 feet. At the time, Cleveland had gone nearly a year and a half without an eruption — the longest time it had gone without one since 2005.
But scientists downgraded the alert level at the volcano to an "unassigned" status back in September after it stopped being active for several months.
Schneider said monitoring activity at Cleveland is difficult because there aren't many local sensors there. Cleveland only has two seismometers on it, which isn't enough to pinpoint the exact location of something like an earthquake, which can cause volcanic unrest.
"We have very little local data," Schneider said. "There are plans in the future to enhance that, but it is a difficult place to get data back from, based on its location."
Schneider said Cleveland has a history of cycles of explosions and that the AVO will continue to monitor the volcano closely and warn nearby communities, aircraft and fishermen of any hazards, if they arise.
As part of the AVO's warning system, he said staff work closely with the National Weather Service to issue guidance to mariners about potential ash fall or other concerning volcanic activity.
"Anytime there's a volcano active in the Aleutians, not only do we worry about the aviation hazard, but also the risk to mariners — both the people that are fishing, as well as cargo ships that are transiting between North America and Asia and sometimes through the Aleutians as well."
Meanwhile, there was also mild explosive activity at Semisopochnoi Volcano in the Rat Islands last week.
Schneider said there's no hazard at this point, but they'll continue keeping an eye on it.