The Alaska Volcano Observatory estimated an explosion at 9:24 a.m. rose to about 60,000 feet, similar to explosions that started the latest eruption cycle late Sunday and early Monday. Thursdays explosions were the 10th measured. The second explosion could be seen rising like a huge white anvil behind Crossman Ridge north of Homer.

Photographer: McKibben Jackinsky, Homer News With ash falling from Redoubt Volcano Thursday afternoon, Ninilchik students and a staff escort wear dust masks as protection as they leave the school building for buses.

AVO scientists had lowered the caution levels to watch and aviation code orange on Wednesday.

"We had no short-term warning. That's what we expected," Stephanie Prejean, a U.S. Geological Survey geophysicist with AVO said this afternoon at a press conference in Anchorage. "At this point, we have a wide-open system."

The ash cloud drifted north-northeast at higher altitudes, with a lower cloud drifting east toward the Kenai Peninsula. About noon on Thursday, that cloud could be seen from Baycrest Hill as a dark-blue and gray band moving east and south. Curling tendrils fell down to Cook Inlet as the ash progressed toward Homer. As the cloud moved over Diamond Ridge, from below it looked an ominous brownish-gray. Specks about the size of a pencil point fell on the snow, slowly darkening it. Where fence posts and buildings blocked the ash-filled wind, reverse shadows of white against gray formed in the dirty snow.

The first reports of ash came from a lodge about 35 miles south of Redoubt, where a man told AVO he could feel it hitting his bare skin, Prejean said. As a snow squall blew in from the north, the ash stung eyes. Fluffy flakes the size of dimes melted into brown-gray blobs on clothing. The ash plume was not expected to fall on Anchorage.

Seismic stations on or near Redoubt measured a lahar, or muddy flow of water and debris, on the Drift River after the second Thursday morning explosion. It was unknown if the lahar damaged the Drift River Terminal about 25 miles from the Redoubt summit.

Engineers from Cook Inlet Pipeline Co. were unable to inspect the Drift River Terminal on Wednesday, Petty Officer Sara Francis, a spokesperson for U.S. Coast Guard public affairs, Anchorage, said at the AVO press conference.

The tank farm at Drift River has dikes around each tank and a larger dike around the entire farm. As of Tuesday, that dike did not appear to have been breached.

Photographer: McKibben Jackinsky, Homer News Ninilchik School Principal Terry Martin displays ash from Redoubt Volcano he collected within five minutes after the ashfall hit Ninilchik Thursday afternoon.

"We're confident with that system and the enhanced dike system we're in good shape," Francis said. "We understand at this time the safest place for that oil to be right now is in those tanks, because the tanks have containment, they have secondary and tertiary containment. A vessel doesn't necessarily have that capacity," she added.

Cook Inlet Spill and Response Inc. was to make soundings of the oil-loading platform off the terminal to see if it had been damaged.

The U.S. Coast Guard captain of the port, western Alaska, has authority to close the facility or call for removal of any oil that's there, Francis said.

Prejean compared this cycle of explosions with the 1989-90 Redoubt eruption, and said these have been shorter than past eruptions, some of which lasted for 40 minutes. AVO planned to make an overflight of Redoubt Thursday afternoon. Scientists have relied solely on seismic and other measurements to analyze this eruption. They have not been able to visually confirm if any dome formation has happened at the summit.. A big unknown is how much magma remains close to the surface and that will rise up, causing further eruptions.

"We could have these large eruptions pretty much at any time," Prejean said. "There will be lulls in this activity."

Michael Armstrong can be reached at michael.armstrong@homernews.com.