The Alaska Volcano observatory reports Tuesday that Cleveland Volcano is erupting with the effusion of lava within the summit crater at the uninhabited island about 940 miles southwest of Anchorage.
Satellite data last week showed a "thermal anomaly," indicating the lava dome was growing.
Observers were able to measure the lava dome at 540 feet in diameter, up from 490 feet Sept. 9.
The lava dome remains about 66 feet below the eastern rim of the summit crater.
The observatory says a growing lava dome increases the possibility of an explosive eruption that could send ash high into the sky.
Lava overflowing the rim is another possibility.
Current dome growth resumed around Sept. 3.
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