Lake held 200 million gallons when Hawaii volcano blew. Here’s how fast it evaporated

Any volcanic eruption offers surprises, but the Sunday eruption of Hawaii’s Kilauea Volcano gave answers to questions scientists hadn’t even asked.

Like, for example: How long does it take 200 million gallons of water to vanish when a volcano erupts beside a lake?

The lake in question was an unnamed body of toxic water that had been growing for 17 months atop Kilauea. Experts feared the combination of water and lava might end in a deadly “steam-blast explosion,” but that didn’t happen.

Instead, the mysterious 154-foot-deep lake was dramatically burned off the planet as thermal cameras rolled.

“The entire volume of the lake was vaporized in about 90 minutes,” James P. Kauahikaua of the U.S. Geological Survey told McClatchy News. “The most recent estimate of water volume in the lake was estimated to be about 850,000 cubic meters or about 200 million gallons.”

That means the water evaporated at a rate of more than 2.2 million gallons per minute ... or about 370,370 gallons per second. The intensity was such that “billows of steam” rose more than 30,000 feet above the volcano, experts say.

The demise of the intensely studied lake came as 8 to 10 million cubic meters of lava poured into the crater from three fissures, the USGS reports. “This is equivalent to over 2 billion gallons, the volume of 3,000 Olympic-sized swimming pools,” it was reported.

As of Friday, Dec. 25, the lava lake had grown to 27 million cubic yards or 4.8 billion gallons, officials said.

Floating atop the lake is an 850-foot-long, 375-foot wide island ”of cooler, solidified lava,” the USGS says.

Why didn’t it explode?

Magma interacting with surface water — or even below-surface water — is a volatile mix that can trigger explosions, geologists say.

“The intense heat of such material (as high as 1,170° C for basaltic lava) may cause water to boil and flash to steam, thereby generating an explosion of steam, water, ash, blocks, and bombs,” the USGS says.

It was a possibility as the lake grew atop Kilauea, experts say. Their fears worsened in recent weeks as the water showed signs of color change and movement: Both have happened at other crater lakes shortly before eruptions, the USGS reports.

“Yes, there was a concern that the water lake could make an eruption more explosive if certain conditions were met. One of the conditions was that lava erupt under the water lake and that apparently didn’t happen,” Kauahikaua told McClatchy News.

“The fissure vents appear to have opened above the lake level on the north and west debris slopes, pouring lava downslope into the lake. The reaction was similar to what happens when lava flows pour into the ocean at the coast. There was instant generation of a massive steam plume.”

The three fissures have worked together to replace the water with a lava pool that is now about 577 feet deep, with 20 feet added in the past 24 hours, the USGS reported Friday. And it’s still growing.

“How high is the lava? If the Empire State Building, in New York City, was placed at the bottom of Halemaumau crater, we estimate the lava lake level could already be as high as the 44th floor!” the USGS reports.

Before vanishing, the crater lake was considered one of the world’s most dangerous bodies of water, with temperatures between 176 and 185 degrees. Water at 154 degrees “instantaneously” scalds human skin, according to Hotwaterlab.com.

The area around Kilauea remains “extremely dangerous” due to “rockfalls and minor explosions (that) may occur suddenly and without warning,” USGS warns.

This story was originally published December 23, 2020 at 10:30 AM with the headline "Lake held 200 million gallons when Hawaii volcano blew. Here’s how fast it evaporated."