VOLCANO, HAWAII - Experts remained flummoxed Friday about when Hawaii's Kilauea volcano will calm down.
The volcano exploded at its summit Thursday, sending ash and rocks thousands of feet into the sky.
Scientists said the eruption was the most powerful in recent days, though it probably lasted only a few minutes.
It came after the volcano had sent lava flows into neighborhoods 25 miles (40 kilometers) to the east of the summit and destroyed at least 26 homes since May 3.
County civil defense officials on Friday reported a new lava vent in the area — the 22nd such fissure.
More explosive eruptions from the summit are anticipated.
“Trying to understand when a volcano is going to stop erupting is nearly impossible, because the processes driving that fall below the surface and we can't see them.” said volcanologist Janine Krippner of Concord University in West Virginia.
She noted that authorities have been able to usher people to safety.
“If nobody warned people, and tourists were all over the place, that would have been devastating with those large rocks flying out — those are deadly,” she said.
The Federal Aviation Administration extended a restriction on aircraft from entering the airspace up to 30,000 feet above sea level. The prohibition applies to a 5-mile (8-kilometer) radius around the crater.
Thursday’s eruption did not affect the Big Island’s two largest airports in Hilo and in Kailua-Kona.
The greatest ongoing hazard is the ongoing lava flows and hot, toxic gases spewing from open fissure vents close to homes and critical infrastructure, said Charles Mandeville of the U.S. Geological Survey's volcano hazards program.
Authorities have been measuring gases, including sulfur dioxide, rising in little puffs from open vents.
“As far as me, I’m not sure whether it would do me any good to stay,” said James Clapper, 70, an evacuated resident now sleeping in his truck. “The property out there has got huge, huge cracks. Is one of those cracks underneath the house? I don't know.”
Hawaii residents are covering their faces to keep from breathing small particles flying through the air after Thursday's eruption.
Lindsey Magnani said Thursday that she and her family, including two young children, picked up masked distributed by county officials and had to close all the windows in their home because the air smelled like sulfur.
Authorities handed out around 2,000 masks for protection for people living near the volcano.
Geologists have warned that the volcano could become even more violent, with increasing ash production and the potential for future blasts to hurl boulders the size of cows from the summit.
After Thursday's eruption, most residents found only thin coatings of ash, if any at all, as winds blew much of the plume away from populated areas.
“It was a grit, like a sand at the beach,” said Joe Laceby, who lives in Volcano a few miles to the northeast of Kilauea's summit. The ash was a bit of an irritant, he said, but “not too bad.”
Laceby sealed windows and cracks in his home with cellophane wrap to keep out ash and volcanic gases. He has gas masks to protect himself from the toxic fumes and ash.
Dr. Josh Green, a state senator who represents part of the Big Island, said the immediate health risk comes from ash particles in the air. Anyone with respiratory difficulties, such as asthma or emphysema, should limit exposure to the ash, he said.
The crater sits within Hawaii Volcanoes National Park, which has been closed for a week as a safety precaution.
Scientists warned May 9 that a drop in the lava lake at the summit might create conditions for a large explosion. Geologists predicted such a blast would mostly release trapped steam from flash-heated groundwater.