©Charlene Meyers. Images of Hawaii
Photographer and national park volunteer Charlene Meyers
took this 72-second time exposure Tuesday night
of the glowing spot in Halemaumau Crater.

Big Island photographer Charlene Meyers must have been one of the last people to see the glowing red vent inside Halemaumau Crater before the unusual feature blew itself apart early Wednesday morning.

Arriving at the Jaggar Museum viewing site at about 9:30 p.m. Tuesday, Meyers found a moment when rain showers did not obstruct the view, a nearly full moon lit the ground and sulfur dioxide steam plume, and a 72-second exposure revealed the Southern Cross hanging just to the right of the blazing, bright red spot.

About five hours later, at 2:58 a.m. Wednesday, the red spot blew up, throwing debris over a 75-acre area.

Tuesday night was the last time anyone had a chance to see it, Meyers said.

The next day, Hawaii Volcanoes National Park closed the Jaggar area for fear of a repeat explosion.

"We are still gathering details and trying to deduce the exact nature of the explosion," the Hawaiian Volcano Observatory said in its weekly "Volcano Watch" column.

One idea is the "throat-clearing hypothesis" -- that the vent system plugged up, then blasted the vent tube open, the observatory said.

A coating of fine white grit, probably from the explosion, was found on cars in Pahala, 19 miles to the southwest.

A boulder weighing 2.7 tons was among the material blown out of Halemaumau Crater.

Sulfur dioxide gas continues to gush from the former site of the red spot.

A state air-monitoring station at Pahala recorded sulfur dioxide levels on Wednesday at nearly 0.15 parts per million, exceeding the U.S. Environmental Protection Agency's limit of 0.14 parts per million during a 24-hour period, the state Department of Health said.

People with breathing problems were urged to stay indoors, limit physical activity and drink plenty of fluids.