An explosive eruption at Hawaii's Kilauea volcano early Thursday created an enormous ash plume that prompted the closure of schools and forced residents to remain indoors as a light ash rained over the surrounding area on the eastern edge of the island.
The ash plume rose as high as 30,000 feet and drifted northeast over the Big Island of Hawaii, Hawaii County officials and the U.S. Geological Survey said. "You should shelter in place if you are in the path of the ash plume," county officials said.
The explosion lasted only a few minutes, meaning the volume of ash produced was relatively small, USGS volcano scientist Michelle Coombs told reporters at a televised news conference. Rain has helped contain the ash, keeping it close to the volcano's summit area.
"If it's a short event, it's just going to have less time to put stuff into the clouds," Coombs said. "This is the kind of event we have been expecting might happen."
National Weather Service meteorologist Kevin Kodama said most of the heavier ash fell close to the summit and near Volcano village, about a five-minute drive from Hawaii Volcanoes National Park. Authorities received reports of a light layer of ash at the nearby Volcano Golf & Country Club.
Ash is primarily a nuisance and can irritate the eyes, cause breathing problems, reduce visibility, make roadways slippery and interfere with electrical lines. Fine ash particles are generally a millimeter or less in size.
Hawaii County officials said they were distributing free masks, one per family member, to protect against the ash. The masks do not protect against toxic gases or vapors.
The explosive eruption occurred at 4:17 a.m. Hawaiian time and forced the closure of half a dozen schools because of elevated levels of sulfur dioxide, a toxic gas, Hawaii County officials announced.
The area southeast of Kilauea volcano's summit is a rural, remote part of Hawaii island, far from any major resort areas. The closest resorts, in Kona and on the Kohala coast, are scores of miles away on the west side of the island.
USGS officials last week said they did not expect evacuations or significant damage from explosive eruptions at Kilauea's summit because it is so far away from populated areas. Leilani Estates, the small neighborhood that has been affected this month by earth-borne lava flows that have destroyed homes and other structures, is 25 miles east of the volcano summit.
Explosions that do occur at the summit pose a risk of bombardment by material that could weigh as much as 10 or 12 tons — but only within an area of about half a mile. There are no inhabited areas within half a mile of Kilauea's summit; the visitors center at Hawaii Volcanoes National Park is about 2 miles away. The National Park Service has ordered most of the park closed.
Locations within several miles of the summit could be subject to being struck by marble-sized rocks or dusted with fine-grain material and ash.
USGS officials said last week that steam-driven explosions at Kilauea were possible. The volcano's recent instability has involved the movement of molten rock to the east of the summit, toward Leilani Estates.
Scientists have observed that the lava lake at the summit has dropped.
That raises the risk for an explosion. Normally, when the lava lake level is high, temperatures are so hot that the groundwater in surrounding rocks is kept away from the magma. But as the lava lake level falls below the groundwater table, water can start interacting with the magma, heating up and creating steam, USGS scientist Donald Swanson said last week.
Rocks can fall from the walls surrounding the magma in the volcano and form a dam. If the steam builds pressure, "it can eventually burst out in an explosion," Swanson said.
Steam-driven explosions were observed at Kilauea in 1924, when there was a similar drop in levels at the lava lake. That event was comparatively more intense; the explosions were stronger and more frequent, lasting more than two weeks. No damage was reported, and only one person died, a photographer who got too close and was hit by falling rocks and hot mud.
There is precedent for a more energetic explosive eruption — in 1790, at least 80 and perhaps hundreds of warriors marching across the summit area died after a hot, fast-moving explosive cloud of volcanic steam and hot ash erupted. A repeat of that type of explosion today would almost certainly destroy the Hawaiian Volcano Observatory, according to the USGS.
But the current conditions at Kilauea suggest that a repeat of the 1790 scenario is "very, very unlikely," said USGS research geophysicist Wes Thelen. Conditions would have to destabilize dramatically for such an eruption, including stronger earthquakes in the summit area.
Hawaiian Volcano Observatory staffers have relocated to the University of Hawaii campus in Hilo because of the observatory's proximity to the eruption site.
In the Leilani Estates area, the USGS said there are still reports of lava spattering out of the ground, but the lava flow has not advanced significantly recently. Scientists, however, said the movement of magma being tracked points to the potential of more lava eruptions in that area.
Some locals close to the volcano described the falling ash as more of a nuisance than a hazard. Karen Kaufman, who was visiting her boyfriend near the golf course in the community of Volcano, said ash on Wednesday was thick enough to cover her windshield. On Thursday, there wasn't as much ash, despite the big explosion that morning.
"I'm not scared at all," Kaufman said.
Yukie Ohashi, who lives nearby with her husband, tried to stick to her daily routine, which includes collecting eggs from her 20 hens.
But even with a respirator, she didn't want to stay outside too long. After washing ash off one car, she gave up on the other and went inside.
"I didn't want to breathe in the bad air," she said.
Some schools were doing their best to hold classes. The Volcano School of Arts and Sciences was one of several to close Thursday, but it planned to reopen Friday.
"We very much want to keep the school open, so we're going to find a way to live with these events," said Kalima Kinney, principal of the school, which serves 207 children, from preschoolers to 8th-graders. "This is what comes with living on a volcano."
Referring to the Hawaiian volcano goddess, Kinney added: "Pele is going to go where she wants to go, and do what she wants to do, and we're just guests here. So we're a little at her mercy right now."
Hawaii state Rep. Richard Onishi, whose district includes Hawaii Volcanoes National Park, said the volcano's eruption was not affecting the state's other five main islands — Kauai, Molokai, Lanai, Maui and Oahu, which includes the state capital, Honolulu.
"The area that's affected by the volcano is only about 20% of Hawaii island. So the west side of Hawaii island and the rest of the state is still operating as usual and is open to visitors," he said.
Onishi said some tourists are avoiding areas that are unaffected by the volcano. For example, an inter-island cruise ship canceled its port of call to Kona, on the other side of Hawaii island, he said.
"The whole island is being affected because the tourists are bailing," said John Dawson, a Hilo resident and a natural history artist. "They don't realize the volcanic activity is only affecting a certain area of a very large island. We're hoping for the best."
Times staff writer Lin reported from San Francisco and special correspondent Chang from Honolulu.
7:00 p.m.: Updated with a quote from the principal of a school and another resident.
4:45 p.m.: Updated with quotes from residents and context about the 1790 and 1924 eruptions at Kilauea.
1:49 p.m.: This article was updated with quotes from USGS volcano scientist Michelle Coombs and National Weather Service meteorologist Kevin Kodama, Hawaii state Rep. Richard Onishi, and details on reports of lava spattering out of Leilani Estates.
10:55 a.m.: This article was updated with additional details, including forced school closures.