An ash cloud erupted some 15,000 feet into the air from Alaska's Cleveland Volcano, according to satellite images and the Alaska Volcano Observatory.
The last significant eruption of Cleveland occurred in February 2001 and resulted in three ash plumes that reached up to 39,000 feet above sea level and "a rubbly lava flow and hot avalanche that reached the sea."
Cleveland, located in the Aleutian Islands about 45 miles west of the community of Nikolski, has been upgraded and downgraded several times over the last few months, flaring up in July and erupting in the form of a growing lava dome in August. Following several weeks of activity, the volcano was downgraded before being upgraded again to an alert level of "watch" and an aviation hazard color-code of "orange" in early September. Two months later, the alert level was again lowered after the volcano seemed to quiet down.
This latest activity comes six days after the most recent update on the AVO website. The AVO said that satellite imagery from about 5 a.m. Thursday confirmed the presence of a detached ash cloud, about 50 miles away from the volcano and moving southeast.
Aviators in the area are encouraged to exercise caution, but the AVO said that the eruption may be an isolated event.
"Satellite data indicate that this is a single explosion event," the AVO said, "however, more sudden explosions producing ash could occur with plumes exceeding 20,000 feet above sea level. Such explosions and their associated ash clouds may go undetected in satellite imagery for hours."
Cleveland volcano lacks any real-time monitoring equipment.
Contact Ben Anderson at ben(at)alaskadispatch.com. Scott Woodham contributed to this report.