Kilauea's Recent Eruption Was Its Biggest in Two Centuries, Scientists Confirm

By Maddie Stone on at

It’s been over three months since fresh lava oozed out of Kilauea volcano, and the eruption that turned southeastern Hawaii into a fiery hellscape has receded from the headlines. But for scientists with the US Geological Survey’s Hawaii Volcano Observatory (HVO), the story is far from over.

These researchers are just beginning to unpack the trove of geophysical, geochemical, and geological data collected during the eruption. But they can now definitively say that Kilauea’s 2018 flank eruption was its biggest in at least 200 years. In the span of about four months, the volcano spilled at least 0.2 cubic miles of lava—that’s over 300,000 Olympic-sized swimming pools of molten rock—over an area of about 13.7 square miles, transforming the landscape and adding more than a square mile of new land to the coast.

These are just a few of the top-line conclusions of a synthesis paper published yesterday in Science. The dramatic sequence of events that unfolded during the eruption—including just the eighth so-called caldera collapse scientists have witnessed at any volcano on Earth since 1900—have given researchers an unprecedented opportunity to answer basic geological questions and improve our tools for predicting future hazardous eruptions.

The action at Kilauea started in early May, when an overflowing lava lake at the volcano’s summit began to rapidly drain, dropping hundreds of feet in a matter of days. This sent magma streaming below the surface some 40 kilometres (25 miles) to the southeast, where it ripped new fissures and triggered earthquakes in a region known as the Lower East Rift Zone (LERZ) beginning on 3 May. Fresh fissures continued to open for weeks as the newly drained summit caldera collapsed in on itself, triggering explosive eruptions of gas and ash.

By the end of May, the eruption had concentrated around Fissure 8, which wound up shooting fountains of lava up to 80 metres (262 feet) into the air, feeding a network of channels that ultimately blazed a trail of destruction all the way to the ocean. Hot, fresh lava continued to flow until 4 August, when things shut off pretty abruptly. By early December, no fresh lava had been seen in the LERZ in three months, meaning the eruption is for all intents and purposes over.

Thanks to the scientific instruments HVO already had in place around Kilauea and the additional resources scientists were able to mobilise as the eruption revved up, researchers have developed a pretty good picture of how magma moved through the system, and they were able to better constrain how much molten rock is stored there. But as USGS volcanologist and study co-author Mike Poland explained, there are still major unanswered questions, including what tipped off the eruption in the first place and why it stopped so suddenly.

Poland explained that the eruption started out looking like many other events in Kilauea’s recent history, with pressure building up at the Pu‘u ‘Ō‘ō vent down-rift of the summit. For the past few decades, inflation at Pu‘u ‘Ō‘ō has caused new lava outbreaks in the area. But this time around, he said, “something ruptured in that deeper part of the plumbing system” that allowed a lot more magma to move much further down-rift into the LERZ.

Why that deep rupture occurred, we still don’t know, and ultimately it might be tough to draw definitive conclusions without any similar events to compare it to. The mystery of why Kilauea shut off virtually overnight, Poland said, is perhaps more within reach once researchers combine all the data collected during the eruption with models of fluid flow.

“This is one of the most well monitored eruptions in the world, and we still couldn’t tell what it was gonna do,” said volcanologist Janine Krippner, referring to the eruption’s abrupt conclusion. “That doesn’t say anything about the lack of expertise—it says everything about the complexity of [the] volcanic system.”

And there are other mysteries to solve, including what set off the explosive eruptions that rocked the summit crater beginning in May. At a press conference at the American Geophysical Union meeting in Washington, DC yesterday, USGS volcanologist Kyle Anderson said that scientists’ initial model of these explosions—as events driven by interactions between magma and groundwater—doesn’t seem to be supported by the new data.

Poland said that even if Kilauea stays quiet for the next 20 years, there’ll be no shortage of things for scientists to puzzle over. In addition to studying all of the data collected during the eruption, HVO researchers now have a rare opportunity to watch the volcano’s magma system rebuild itself after a massive bleed-out.

“It’s a cornucopia of opportunity,” Poland said. “There’ll be dozens of new things that come out of this.”

Krippner, who wasn’t involved with the new paper, echoed Poland’s sentiment. “I think there are going to be multiple lifetimes spent on this data,” she said.

Featured photo: US Geological Survey (AP)