Large explosion at Kilauea’s summit likely steam-driven, creating ashfall hazards


 At 4:17 a.m. Thursday, while most people were still asleep, the biggest explosion so far over the past two weeks took place at Kilauea’s summit, spewing ash and steam as high as 30,000 feet.

“Fortunately, it was short-lived and it went down pretty quick, and it didn’t have really a wide impact,” said Talmadge Magno, Hawaii County Civil Defense administrator. “Like Hawaiian Volcano Observatory has been saying, it’s been fine stuff that’s been going to the communities, but any bigger debris sounds like it’s probably within the park, which is closed.”

There’s been talk of the so called “big one” happening, however scientists at the U.S. Geological Survey Hawaiian Volcano Observatory say there’s not going to be just one big one, but more like a series of steam-driven explosions that are bigger than anything we’ve seen in the past 10 years.

The one Thursday morning was certainly one of the big ones.

“At least based on the 1924 experience, the explosion is a series of explosions. They don’t build up to a biggest one. They vary in strength throughout the period,” explained USGS geophysicist Jim Kauahikaua.

Explosive steam eruptions happen when the lava lake drops below the water table. The water comes into contact with the magma and the water turns into steam. When rocks from the crater wall fall down, blocking the opening, you have all that steam buildup and it eventually erupts, sending steam, ash, and some rocks along with it.

“But the evidence is difficult to come by at this point, and so it’s like we can’t quite go into the crater and gather the evidence. It becomes dangerous to do so, we’re kind of waiting for the right time to get that evidence,” said Kauahikaua.

During the steam-driven explosions back in 1924, that series lasted for two and a half weeks.

“They sort of die off. Over the last few days of 1924, the explosion sort of died. The seismicity dropped off,” Kauahikaua said.

What we’ve been seeing over the past week, and what we witnessed starting last week Wednesday coming out of Halemaumau Crater, are gas explosions.

Scientists believe Thursday’s explosion was steam-driven, which is much more powerful. That’s why Hawaii Volcanoes National Park is closed.

“The event early this morning was a little different. We had anticipated that, and we had prepared for the event. It was relatively short-lived as you know, but clearly the ash and the fallout is still with us,” said Gov. David Ige.

On Wednesday, USGS scientists found rocks that measured two feet across in the parking lot a few hundred yards from Halemaumau Crater.

“We have a bit of evidence in the ashfall that came out this morning. We gathered a number of samples of ash from different places,” Kauahikaua said. “We can’t go into the caldera. It’s too dangerous at this point to see what else is out there, because the larger pieces will only fall around Halemaumau Crater,” he added.

While scientists say Thursday’s ashfall was somewhat mitigated by rain, residents were warned to shelter in place, either indoors or in vehicles with the windows closed.

“The difference is if you walk around and you notice the top of fence posts and signs, there’s a thin dusting of ash,” said Jessica Ferracane, Hawaii Volcanoes National Park public relations specialist.

You may not see it, but other areas are feeling a difference. Mary Evangelista lives in Pahala, more than 20 miles south of Volcano.

“At times I have a hard time breathing,” she said. “Runny nose and my eyes burn.”

Affected residents got the help they needed. Manufacturer 3M donated 18,000 N95 masks that were passed out in Volcano, Pahala, Naalehu, and Keaau.

Officials stress that the masks are designed to filter out volcanic ash, and do not protect against toxic gases like sulfur dioxide.

Masks were distributed until 7 p.m. at the following locations:

  • Cooper Center, Volcano
  • Pahala Community Center, Pahala
  • Naalehu Community Center, Naalehu
  • Shipman Park Pavilion, Keaau 

Distribution will continue on Friday from 1 to 7 p.m. at Cooper Center and Ocean View Community Center.

One mask per family member was allowed to assure supplies lasted throughout the day.

Officials also advise the following:

  • Ash fallout may cause poor driving conditions, due to limited visibility and slippery driving conditions. Drive with extreme caution, or pull over and park.  
  • After the hazard has passed, do check your home, and especially your catchment system for any impact that may affect your water quality.

Click here for more information on how to protect yourself from ashfall.


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