July 15, 2008—This is one time when you'd want the window seat.

Kelly Reeves of Alaska Airlines snapped the above photo as a plane flew above an Aleutian Islands volcano on July 13, 2008, the day after its first violent eruption.

The July 12 explosion of the 3,500-foot (1,067-meter) Okmok Volcano on Umnak Island spewed ash and sulfur dioxide 50,000 feet (15,240 kilometers) high, and the materials have since formed into a large mass hovering above the North Pacific.

The new eruption is more intense than the volcano's past three major events in 1945, 1958, and 1997, according to a statement by the Alaska Volcano Observatory. This explosion is uniquely water-rich, due to the mixing of rising magma and shallow groundwater, the statement said.

(Read about another volcano that erupted in Alaska in 2006.)

Ten people who live on Umnak Island were evacuated, and nearby Unalaska Island has been covered with a light ashfall, Jennifer Adleman, a geologist with the Alaska Volcano Observatory, told Reuters news service.

"There have been reports of eye irritation and people being able to taste it, if you will," Adleman said. "Some folks have seen it on their windshields."

Observers predict lava will eventually spill from the caldera, and that activity will continue for several weeks and possibly longer.

—Christine Dell'Amore