The Pavlof volcano in Alaska's Aleutian Islands showed signs of activity Sunday, prompting the United States Geological Survey to issue a flight bulletin urging airlines to avoid the area.
The volcano sent ash 6,500 yards into the sky, potentially endangering between 20,000 and 30,000 passengers who fly in the area each day.
Scientists are monitoring the volcano and Alaska Volcano Observatory issued a red alert for the area. On Tuesday, the alert level was yellow,
according to the AVO website. Yellow means the volcano "is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase."
The Alaska Dispatch News reported that the alert level at the volcano was raised Friday after seismic activity was noted and minor steam emissions were observed.
Pavlof has had 40 historic eruptions, including two earlier this year, occurring in March and May. The March eruptions shot ash plumes 40,000 feet above sea level.
Pavlof is about 600 miles southwest of Anchorage on the southwestern end of the Alaska Peninsula. Scientists are monitoring it closely as eruptions can occur with little or no warning,
according to The Christian Science Monitor.
The chance for another eruption before the end of the year is "highly likely,"
Tech Times reported.
Cleveland Volcano, another volcano in Alaska's Aleutian Islands, has also shown signs of unrest.