The explosion geologists feared from Hawaii's volcano has just happened

Nature


Hawaii’s Kīlauea volcano erupted explosively early Thursday, tossing boulders hundreds of feet and sending a plume of ash about 30,000 feet (9,144 metres) into the predawn sky.

 

A webcam at the Hawaii Volcano Observatory caught the aftermath of the short-lived eruption: an onslaught of wet, dusty ash raining on a darkened landscape.

From the summit of Mauna Loa volcano, 20 miles (32 km) away, cameras photographed an anvil-shaped plume billowing on the horizon.

In a news conference, scientist Michelle Coombs of the US Geological Survey said the activity could become explosive again.

“It’s a real dynamic situation up there,” she said of the summit.

webcam overlook multimediaFile 2038View of the ash plume (USGS)

Scientists had warned for days about a major eruption as the lava lake that once filled the crater at Kīlauea’s summit began draining back into the ground.

Their concern was that the sinking molten rock would create steam as it interacted with the water table and that the steam would then jet upward, hurling heavy rocks and ash into the sky in a phenomenon known as a phreatic eruption.

“This is the sort of explosive activity that was anticipated,” said USGS geophysicist Mike Poland, who was based at Kīlauea from 2005 to 2015. “It’s not going to be the only one. Very likely there will be additional events.”

 

Hawaii Volcanoes National Park officials said the caldera – the depression at the center of the volcano – dropped more than three feet (900 cm) overnight, triggering frequent earthquakes that have cracked highways in the area.

As the caldera sinks further, it may set off additional steam-driven explosions, they said.

Though dramatic, Thursday’s eruption at 4:15 am local time did not pose an immediate threat to people in the vicinity, Poland said.

Observatory staff had left their Kīlauea station Wednesday, for a facility at the University of Hawaii at Hilo, after concluding that wind could carry ashfall their way.

According to Poland, the greatest impact was to an area within a few hundred yards of the summit’s eruptive vent.

That’s where the explosion would have sent hot gas and 1,000-pound (450 kg) rocks soaring. For this reason, the national park has been closed since last week.

Wind is already carrying the plume from the eruption northeast, raining ash into nearby communities. Broadcasting on local radio stations, Hawaii Civil Defense officials warned that ash poses the main health threat from the eruption.

 

Residents were instructed to shelter in place if they found themselves in the path of the plume.

Depending on weather conditions, the USGS said, ash might fall as far as Hilo, 30 miles (50 km) to the northeast.

The observatory also warned that vog – a noxious smog formed when sulfur dioxide from eruptive vents interacts with water vapor and oxygen in the air – has been reported in the community of Pahala, southwest of the volcano.

Meanwhile, stormy weather caused the ash to mix with rain, creating a dark paste that coated rooftops and car windshields.

In the village of Volcano, barely three miles from the summit, lifelong resident Lance Benevides went through the familiar protocol to cope with an eruption, including detaching his roof gutters from his water tank to keep ash out of the catchment system that serves as his water supply.

Then he headed to the Volcano Store, a local gathering spot, where he sat with friends and sipped coffee Thursday morning – a ritual not even Kīlauea could disturb. “We all live in a circle around this volcano,” said Benevides, 55. “So we know what to do.”

USGS scientists use Ash3D computer simulations to show how far ash might travel and how much ash might fall to the ground. This graphic shows today’s simulation (May 17) for the explosive eruption at Kīlauea’s summit. https://t.co/Ds1pWnFRVw pic.twitter.com/hGCoTBon1X

— USGS Volcanoes

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