Bogoslof volcano map
© Alaska Volcano Observatory
An Alaska volcano active since mid-December has erupted again.

Bogoslof Volcano in the Aleutian lslands erupted at 1:20 p.m. Wednesday and sent up an ash cloud that pilots reported was estimated at 31,000 feet.

"Bogoslof volcano is in an active eruption sequence that began on December 16, though retrospective analysis suggests unrest may have started earlier in December," the Alaska Volcano Observatory website explained.

AVO raised the aviation threat code to red, the highest level. Ash clouds higher than 20,000 feet are a threat to intercontinental jet aircraft because ash can damage engines.

Satellite imagery indicates the cloud was moving to the northeast over the Bering Sea. AVO has no recording equipment on Bogoslof Island, but uses long-range equipment on nearby islands, as well as satellites, to monitor the volcano's activity.

Bogoslof Volcano is 850 miles southwest of Anchorage.