A volcano in the Aleutian Islands coughed up an ash cloud Monday, prompting the Alaska Volcano Observatory to raise the mountain's threat level to code red.
Satellites detected the cloud after it detached from the summit of 5,676-foot Cleveland Volcano, located near the Aleutian chain's halfway point. Code red, the highest threat level, means a significant eruption is occurring.
The Federal Aviation Administration issued a temporary flight restriction in a cylindrical area around the volcano below 50,000 feet and within a roughly six-mile radius, said spokesman Allen Kenitzer.
Scientists said the 22,000-foot high ash cloud is relatively small, about two miles long, but could still be a menace to flights in the area. No communities are expected to receive ash fallout, and there are no signs of continuous ash emissions.
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"In terms of people on the ground there isn't a danger, but the air traffic out there can be highly affected," said Janet Schaefer, a geologist with Alaska's Division of Geological and Geophysical Surveys.
Cleveland, on uninhabited Chuginadak Island, last erupted in July. Normal eruption activity includes short-lived explosions of ash from the summit, the observatory said.
Ash from the volcano has blocked air routes in the past.
Airlines redirected trans-Pacific flights after three explosions on Feb. 19, 2001, and interstate flights in western Alaska were canceled that day.
It's the second volcano to erupt in Alaska this year. Augustine Volcano in south-central Alaska began spewing ash in mid-January.