Scientists have raised an aviation alert level around a remote Alaskan volcano after a small eruption produced an ash cloud several miles high.
Cleveland Volcano, on the Aleutian Islands southwest of mainland Alaska, erupted briefly Tuesday afternoon, creating an ash cloud at an estimated height of 23,000 feet above sea level, said Steve McNutt, aÂ volcano seismologist at theÂ Alaska Volcano Observatory and the University of Alaska Fairbanks.
The observatory on Tuesday raised its color-coded alert for aviators to orange, the second most serious of four levels, and warned on its website that "additional sudden explosions of blocks and ash are possible with little or no warning."
No activity was detected Wednesday, but the alert remained at orange, the observatory said.
A more serious eruption, especially one that spews ash above 30,000 feet, could affect air travel. McNutt said the vast majority of air freight between Asia and North America and between Asia and Europe flies over Alaskan airspace. Also, passenger flights take about 20,000 passengers over Alaskan airspace daily, he said.
Tuesday's cloud appeared to dissipate after about two hours, McNutt said, citing satellite images.
The volcano makes up the western half of uninhabited ChuginadakÂ Island, part of the Aleutian Island chain in the Bering Sea. It is about 45 miles west of Nikolski and 940 miles southwest of Anchorage.
The alert level has bounced between orange and the lower step, yellow, several times in the past year. The observatory last issued an orange alert in late March, when satellite images showed a lava dome had formed in the summit crater.
The volcano's most recent significant eruption happened in February 2001, with three explosions that led to ash clouds as high as 7.5 miles above sea level, according to the observatory. The volcano's elevation is 5,676 feet.
Last year, volcanic ash fromÂ Iceland's Grimsvotn Volcano forced the cancellation of hundreds of flights across Europe.
The GrimsvotnÂ eruption came about 13 months after Iceland's Eyjafjallajokull Volcano put ash and smoke into the sky, forcing the cancellation of thousands of flights per day during the peak of the problem.
- CNN's Jason Hanna and Darrell Calhoun contributed to this report.