Here’s what was surprising about Kilauea’s 3-month-long eruption

WASHINGTON — After a stunningly explosive summer, Kilauea, the world’s longest continuously erupting volcano, finally seems to have taken a break. But the scientists studying it haven’t. Reams of new data collected during an unprecedented opportunity to monitor an ongoing, accessible eruption are changing what’s known about how some volcanoes behave.

“It was hugely significant,” says Jessica Larsen, a petrologist at the University of Alaska Fairbanks, and “a departure from what Kilauea had been doing for more than 35 years.”

The latest eruption started in May. By the time it had ended three months later, over 825 million cubic meters of earth had collapsed at the summit. That’s the equivalent of 300,000 Olympic-sized swimming pools, Kyle Anderson, a geophysicist with the U.S. Geologic Survey in Menlo Park, Calif., said December 11 in a news conference at the annual meeting of the American Geophysical Union.

As the summit crater deflated, magma gushed through underground tunnels, draining out through fissures along an area called the lower eastern rift zone at a rate of roughly 50 meters per day. That lava eventually covered 35.5 square kilometers of land, Anderson and his colleagues reported in a study published December 11 in Science.

The volcano also taught scientists a thing or two.

Caldera collapse

Scientists previously believed that groundwater plays a big role in how a caldera collapses. When craters were drained of their magma, “cooling, cracking depressurized the caldera, allowing groundwater to seep in and create a series of explosive eruptions,” Anderson said. “But groundwater did not play a significant role in driving the explosions this summer.”

Instead, the destruction of Kilauea’s crater is what’s called a piston-style caldera collapse, he said. Sixty-two small collapse events rattled the volcano from mid-May to late August, with each collapse causing the crater to sink and pushing the surrounding land out and up. By the end, the center of the volcano sank by as much as 500 meters — more than the height of the Empire State Building.

That activity didn’t just destroy the crater.  “We could see surges in the eruption rate 40 kilometers away whenever there was a collapse,” Anderson said.

Life finds a way

Under the sea, life moved in around the brand-new land surprisingly quickly. Using a remotely operated vehicle to explore the seafloor, researchers in September found evidence of hydrothermal activity along newly deposited lava flows about 650 meters deep. More surprising, bright yellow, potentially iron-oxidizing microbes had already moved in.

“There’s no reason why we should have expected there would be hydrothermal activity that would be alive within the first 100 days,” Chris German, a geologist at Woods Hole Oceanographic Institution in Falmouth, Mass., said at the news conference. “This is actually life here!”

The discovery suggests “how volcanism can give rise to the chemical energy that can drive primitive microbial organisms and flower a whole ecosystem,” he said.

Studying these ecosystems can provide insight into how life may form in places like Enceladus, an icy moon of Saturn. Hydrothermal activity is common where Earth’s tectonic plates meet. But alien worlds don’t show evidence of plate tectonics, though they can be volcanically active, German says. Studying how hydrothermal life forms near volcanoes that aren’t along tectonic boundaries on Earth could reveal a lot about other celestial bodies.

“This is a better analog of what we expect to them to be like,” says German, but “it is what’s least studied.”

What comes next

As of December 5, Kilauea had not erupted for three months, suggesting it’s in what’s called a pause – still active but not spewing lava. Observations from previous eruptions suggest that the next phase of Kilauea’s volcanic cycle may be a quieter one. But the volcano likely won’t stay quiet forever, says Christina Neal, the head scientist at the USGS Hawaiian Volcano Observatory and a coauthor of the Science paper. “We’re in this lull and we just don’t know what is going to happen next,” she says.

Scientists are tracking ground swelling near the Puu Oo vent, where much of Kilauea’s lava has flowed from during the volcano’s 35-year eruption history. That inflation is an indication that magma may still be on the move deep below.

The terrain surrounding this remote region is dense with vegetation, making it a difficult area to study. But new methods tested during the 2018 eruption, such as the use of uncrewed aerial vehicles, for example, could aid in tracking the recent deformation.

Scientists are also watching the volcano next door: Mauna Loa. History has shown that Mauna Loa can act up during periods when Kilauea sleeps. For the past several years, volcanologists have kept an eye on Kilauea’s larger sister volcano, which went silent last fall, after a period with few earthquakes and intermittent deformation. “We’re seeing a little bit of inflation at Mauna Loa and some earthquake swarms where it had been active, Neal says. “So that’s another issue of concern for us going into the future.”