ANCHORAGE, Alaska—The Cleveland Volcano has begun to form a new lava dome, indicating the mountain could send up an ash cloud that might threaten aircraft and prompting scientists to raise the Aleutian Islands volcano’s alert level.
The Alaska Volcano Observatory on Tuesday elevated the alert level for Cleveland to Watch and its aviation color code to Orange.
There have been no eruptions since Dec. 25 and Dec. 29, which destroyed the earlier lava dome built up over the fall.
Cleveland is a 5,675-foot peak on an uninhabited island 940 miles southwest of Anchorage.
Authorities say sudden eruptions could occur at any time, and ash clouds 20,000 feet above sea level are possible.