Scientists have downgraded the aviation alert level for Cleveland Volcano from orange to yellow.  

The volcano lies on a major international flight path and on December 29, it put up a 15,000 foot ash cloud.  That prompted the Alaska Volcano Observatory to increase the warning level, even though the plume wasn’t expected to interfere with aviation.

Scientist-in-charge John Power says they’ve lowered the alert because the ash cloud has dissipated.  He says they still don’t know exactly what happened to the lava dome that’s been forming in the crater since early July.

“We, at this point in time, don’t have any really detailed imagery or any further information on what’s happened in the crater following yesterday morning’s explosion.”

Historically Cleveland has been a very active volcano.  Its last major eruption in 2001 sent up a series of three plumes, some of them reaching 39,000 feet.

Power says he suspects Cleveland isn’t done with this phase just yet.

“Given that it’s been so active since last June or July up ‘til now, we do expect to see more going on here over the next, coming weeks to months and we’ll certainly update the information on our webpage and so on as conditions change.”

There’s no real-time monitoring network on Cleveland, but the Observatory does have an alert system that can detect the lightning that accompanies major ash clouds within minutes.  Yesterday’s eruption wasn’t large enough to produce lightning - it showed up later on satellite imagery.