A volcano that has been erupting for several days in Alaska's Aleutian Islands may be preparing for a more explosive event, scientists said Wednesday.
Cleveland Volcano, a 5,676-foot peak located on Chuginadak Island, about 940 miles southwest of Anchorage, has been in low-level eruption since the end of July, the Alaska Volcano Observatory said.
"An eruption for us is any time that magma is coming up from the surface in the ground," said John Power, scientist in charge at the observatory, a joint federal-state operation. "This is very much happening here."
Chuginadak Island is uninhabited and the volcano has not posed an immediate hazard to anyone — nor has it affected air traffic, even though it lies directly in the North America-to-Asia flight corridor used by major airlines, Power said.
But there is a possibility that the extrusion of lava is a precursor to a big explosive event that would send ash into the atmosphere, he said.
The dome, if it continues to grow, could plug up the crater, creating pressure that could result in "a fairly sizable explosion that could throw ash up to flight levels," Power said.
The Alaska Volcano Observatory first reported the eruption a week ago, when satellite images showed that the lava dome on the volcano's summit was widening.
Cleveland Volcano covers about half of Chuginadak Island. The closest community to the volcano is Nikolski, an Aleut village of about 20 people located 45 miles to the east.
The fishing port of Unalaska/Dutch Harbor is about 150 miles to the east of the volcano.
Cleveland's last major eruption was in 2001, but it has had several smaller or suspected ash-spewing eruptions since then.
The extrusion of lava into a bigger summit dome is not typical for this volcano, Power said. "This is something we really haven't observed at Cleveland before," he said. However, dome-building events have preceded big explosive eruptions at other Alaska volcanoes, including Redoubt Volcano near Anchorage, he said.
Redoubt's 2009 eruptions caused numerous flight cancellations, as well as a disruption of offshore oil production in nearly Cook Inlet.