Alert level raised as Alaska volcano forms lava dome

The warning level for a remote Alaska volcano has been raised after a new lava dome began forming, indicating the mountain could explode and send up an ash cloud that could threaten aircraft.

The Alaska Volcano Observatory on Tuesday elevated the alert status for Cleveland Volcano.

It said it was raising the Aviation Color Code to orange, which is one step below the highest warning of red.

An orange warning is characterized as "exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions," according to the observatory.

Officials said the new lava dome was spotted in the summit crater. The observatory said as of Monday, the dome was about 130 feet in diameter.

There have been no eruptions since Dec. 25 and Dec. 29, which destroyed the earlier lava dome built up over the fall.

An eruption in 2001 produced ash clouds as high as 39,000 feet, the observatory said.

Cleveland is a 5,675-foot peak on an uninhabited island 940 miles southwest of Anchorage.

Authorities said sudden eruptions could occur at any time, and ash clouds 20,000 feet above sea level are possible.

In 2010, the Eyjafjallajökull volcano in Iceland erupted, sending out a giant ash cloud that grounded flights over much of Europe.