ANCHORAGE — Rumblings under Alaska’s Pavlof Volcano have diminished, but scientists are keeping an eye on the state’s most active volcano in case it sends up another ash cloud.

The volcano sent an ash plume to 22,000 feet Monday, and it drifted east about 50 miles, prompting the Alaska Volcano Observatory to raise the aviation warning in the area to red, the highest level.

By Tuesday, the cloud was below an altitude of 20,000 feet. The observatory Tuesday night lowered the warning back to orange, from “warning” to “watch,” after 12 hours of lower tremors.

The eruption plume had split into two parts, and the higher plume was mostly steam and gas with little ash that could threaten aircraft, the observatory said.

The 8,262-foot Pavlof Volcano is 625 miles southwest of Anchorage on the Alaska Peninsula, the finger of land extending southwest from the mainland toward the Aleutian Islands. Pavlof is a conical volcano, nearly symmetrical, a giveaway that its eruptions tend to be less violent than the kind that blows the tops off mountains, said Game McGimsey, a volcanologist at the observatory.