"Cleveland

Cleveland Volcano, Alaska (NASA)

An eruption advisory has been issued by the Alaska Volcano Observatory for the 5,676 foot-tall (1,730 meter) Cleveland Volcano, located in the uninhabited island of Chuginadak in the Aleutian chain, which is roughly 940 miles (1,500km) southwest of Anchorage.

The advisory comes after "thermal anomalies" were detected by satellite images, the observatory said on Thursday.  The measurements indicate that Cleveland Volcano may erupt at any moment, hurling ash clouds up to 20,000 feet (3.7 miles/6km) above sea level.  The observatory cautions that this could happen with little further warning.

Airlines across the globe are preparing for possible travel chaos.

Cleveland Volcano, like others in the Aleutian chain, lies directly below the commercial airline flight path between North America and Asia.  Consequently, a major eruption could severely disrupt international air travel.

So far, airlines have not changed their flight patterns because of Cleveland's heat emissions, said Steve McNutt, a University of Alaska Fairbanks scientist who works at the observatory.

"Cleveland is a particular bugaboo for us because it is right on the air route" with no seismic equipment, said John Power, scientist-in-charge at the Alaska Volcano Observatory.

Cleveland Volcano last erupted in 2001, when it blasted ash more than 5 miles (8km) into the air and spewed lava from its summit crater.  Several smaller eruptions occurred in the ensuing years.

Because the nearest settlement is 45 miles (72km) away in Nikolski, scientists are not always sure what is happening at the remote volcano.  Although Cleveland is among the most active of Alaska's roughly 90 volcanoes, no seismic equipment is set up there because the costs of working in such a remote area are prohibitive, observatory officials said.