A 16-minute eruption by an Alaska volcano sent an ash cloud up to 36,000 feet (10,973 meters) in the Aleutian Islands.
The Alaska Volcano Observatory says Bogoslof Volcano erupted near 1 p.m. Sunday.
The observatory says the cloud, which was moving east, was not expected to drop ash on Aleutian communities or the mainland.
Ash clouds above 20,000 feet (6,100 meters) can harm airliners flying between Asia and North America. The observatory raised the aviation alert code to "warning" level, the highest level.
Game McGimsey, a research geologist with the observatory, says the observatory will reassess the color codes early Monday.
Bogoslof has erupted periodically since mid-December.
The volcano is 850 miles (1,400 kilometers) southwest of Anchorage.