The U.S. Geological Survey put out an orange alert Thursday for Cleveland Volcano in the Aleutian Islands, about 940 miles southwest of Anchorage. That is third out of four possible levels on the federal agency's warning scale.
"Satellite data indicate that this is a single explosion event," the survey and Alaska Volcano Observatory said in its notice, but "more sudden explosions producing ash could occur with plumes exceeding 20,000 feet above sea level,"
A similar alert had been issued in early September, amid concerns that the volcano could be leaking from its flanks if the lava inside continued to build up. The volcano's lava dome was 262 feet in diameter on August 30, but by then in had expanded to 394 feet.
That warning was downgraded to yellow on November 3.
According to the observatory, satellites spotted a "detached drifting ash cloud" some 15,000 feet above sea level around 7 a.m. (1 p.m. ET) and moving east-southeast.