A swarm of small earthquakes began Monday at Mount Redoubt in what scientists said was a warning that the volcano could be waking from its slumber.
"It is reminding us that it is an active volcano," said Rick Wessels, a geophysicist with the U.S. Geological Survey in Anchorage.
The small quakes started about 1:45 a.m. near the summit of Mount Redoubt, a 10,197-foot volcano about 100 miles southwest of Anchorage. The regular pattern of the tremors are often seen when magma is moving inside a volcano, Wessels said.
Researchers plan to fly through the steam plume of the volcano later this week and measure three chemical compounds linked to volcanic activity -- sulfur dioxide, carbon dioxide and hydrogen sulfide.
Scientists do not know if the earthquakes will lead to the volcano again becoming explosive, but they said that was a heightened possibility.
Redoubt has erupted several times since the 1960s. Its last major eruption was last winter and spring, including 19 significant eruptions over several weeks that sent ash plumes as high as 65,000 feet and cloaked parts of Southcentral Alaska in up to a half-inch of ash.
Residents donned face masks and covered their cars and trucks to keep the ash off the finish and out of the engines.
One eruption caused a mudflow that partially flooded the Drift River Oil Terminal near the mountain's base.
The volcanic eruptions also caused hundreds of flights to be diverted from Anchorage over concerns that an ash cloud could damage airplane engines.
On Monday, said Steve McNutt, a University of Alaska Fairbanks research professor, "We were going along quietly and all of a sudden, boom, we started getting these small earthquakes."
The Anchorage Daily News/adn.com contributed to this story.