Five explosive things the 2018 eruption taught us about Kilauea

After a stunningly volatile 2018, Hawaii’s Kilauea volcano, which had been continuously erupting since 1983, finally seems to be taking a break. Following 35 years of nonstop activity, no lava is currently flowing from the Big Island’s most famous volcano.

Scientists thought they knew Kilauea pretty well. It’s one of the most closely monitored volcanoes in the world, with instruments watching the volcano’s every move since the early 1900s. But the 2018 eruption still managed to offer up surprises.

“Everybody’s chewing on all the great data collected from this eruption,” says Christina Neal, the head scientist at the U.S. Geological Survey’s Hawaiian Volcano Observatory on the Big Island. “That will go on for years and years.” Neal coauthored a study published in the Jan. 25 Science describing some of the initial findings.

The latest episode started last May, as lava drained from the summit crater, flowing out at a rate of 50 meters per day. The molten rock gushed through underground tunnels and out linear eruption vents, or fissures, along an area called the lower East Rift Zone. By the time the eruption ended in August, Kilauea had destroyed more than 700 houses, covered 35.5 square kilometers of land and added almost 300 hectares of land along the island’s southeast coast.

In addition, more than 825 million cubic meters of earth from the area around the summit crater collapsed, deepening Kilauea’s caldera. That’s enough material to fill about 300,000 Olympic-sized swimming pools, Kyle Anderson, a USGS geophysicist in Menlo Park, Calif., said December 11 in Washington, D.C., at an American Geophysical Union meeting.

With the massive collapse, the cliff-hugging Jaggar Museum, Hawaii Volcanoes National Park’s popular museum and research station, suffered damage and is closed indefinitely.

No one knows what’s next for the volcano, but five early findings from Kilauea’s latest outburst, described below, show some of Kilauea’s distinctive impacts.

1. Really old lava explains why some fissures were extra explosive.  

On May 13, lava suddenly exploded from a new fissure along the lower East Rift Zone. “There was this really loud banging that sounded like cannon shots,” says Christoph Kern, a geochemist at the USGS Cascades Volcano Observatory in Vancouver, Wash. Kern was working in the rift zone at the time.

Blocks of rock and ash flew hundreds of meters into the air. “It was reminiscent of a war zone,” Kern says. One man, who had not evacuated from his nearby home, suffered a shattered leg after he was struck by molten rock blasted from the fissure.

When the lava cooled enough for researchers to collect samples, the scientists were shocked. Kilauea “erupted a magma like we’ve never seen before” in Hawaii, says Cheryl Gansecki, a volcanologist at the University of Hawaii in Hilo.

“When I first got the analysis back, I told my student, ‘You’ve made a mistake; go do it again,’ ” she says. The molten rock was andesite, which is not usually found in Hawaii.

The Hawaiian Islands are dominated by basalt, a dark volcanic rock rich in iron and magnesium. Andesite contains more silica and gas bubbles than basalt. That extra gas makes eruptions extra explosive. Andesite is commonly ejected from volcanoes in regions where tectonic plates slip beneath one another, such as in the Andes in Chile or the Cascades in the Pacific Northwest. Hawaii, however, isn’t near a tectonic plate boundary; its volcanoes are fueled by a “hot spot,” a plume of magma that rises from Earth’s interior.

The andesite was also much older than lava erupted from nearby fissures, Gansecki says. She suspects the andesite might have evolved from basaltic magma that was trapped underground during a previous eruption or from very deep molten rock that gradually crept up toward Earth’s surface over time. When basaltic magma cooks beneath Earth’s surface for a long time, some crystals may slowly solidify and settle out of the liquid, changing the overall chemistry of the rock.

“We kind of knew that these magmas were sitting around a little bit and then getting pushed to the surface,” but seeing a lava type with minerals this changed on the island was a first, Gansecki says. Being aware that these pockets of older, gas-rich magma exist will help scientists better prepare for the potential of explosive eruptions at Kilauea.

2. Lava traveled far and fast.

The 2018 eruption peeled back Earth’s layers to reveal that Kilauea’s plumbing system — from the summit crater to 24 active fissures — is very clearly connected, says geophysicist Ingrid Johanson of the USGS Hawaiian Volcano Observatory.

Scientists tracked the volcano’s activity in exquisite detail. Within minutes of a collapse at the summit, tiltmeters, which measure small vertical shifts in Earth’s surface, registered pressure pulses along the East Rift Zone. Within hours, scientists saw increased levels of lava gushing out of fissures more than 40 kilometers from the summit.

Volcanologists witnessing collapses at the summit were able to warn colleagues who were inspecting lava flows along the lower East Rift Zone. “Word would go out to the field geologists: ‘Be on guard in a couple of hours; we think there’s going to be a pulse,’ ” Johanson says.

Surges in lava flow can cause a river of molten rock to spill over the sides of a fissure’s channel — a danger to geologists working near the fissures. Fortunately, no researchers were injured by these overflows.

3. The caldera collapsed in stages.

This most recent activity gave scientists a rare chance to study the collapse of a caldera. Only seven other caldera collapses have been observed worldwide since 1900 — and never with this level of detail, Anderson says. In 2014, for instance, Iceland’s Bárðarbunga volcano experienced a similar “piston-style” caldera collapse, in which a large block of land sinks down into a volcano’s magma chamber below. But that remote collapse was obscured by snow and ice, making it difficult to monitor.

Surprisingly, 62 small collapses rattled Kilauea from mid-May to late August rather than a single, big one. Each collapse spurred more than 700 earthquakes and caused the crater floor to sink further, pushing the surrounding land out and up. By the end, the center of the volcano was more than 500 meters lower than when it started — more than the height of the Empire State Building.

The collapses seemed to happen at regular intervals — roughly every 25 to 35 hours, Kern says. That was the amount of time it took for enough pressure to build inside the magma chamber, at which point gas escaped through cracks around the summit crater, sending rock and ash into the air. With the pressure release, the caldera sank further.

4. Microbes moved in quickly.

Where the eruption flowed into the ocean, marine life sprouted along newly deposited lava flows surprisingly fast. Using a remotely operated vehicle to explore the seafloor, researchers in September found bright yellow, potentially iron-oxidizing microbes in areas of hydrothermal activity about 650 meters deep, just offshore.

“I wondered if we were in the right place,” says geologist Chris German of Woods Hole Oceanographic Institution in Massachusetts. “But I could see the fresh walls of lava still steaming on the shoreline.” It had been only 100 days since lava first entered the water. “We really were in the right place, and it had been colonized,” he says. German and colleagues are now trying to identify the species of microbe.

Studying these new ecosystems may help explain how life could form in hydrothermal environments elsewhere in the solar system, such as Saturn’s moon Enceladus (SN: 5/13/17, p. 6). On Earth, hydrothermal activity is common where tectonic plates meet — not a good analog for alien worlds, which appear to lack plate tectonics. But other worlds can be volcanically active, German says. Observing hydrothermal systems fueled by Kilauea and other volcanoes that aren’t along tectonic boundaries could reveal a lot about the conditions on other celestial bodies.

5. Sulfur dioxide gas levels went through the roof.

In 2018, Kilauea belched out some of the highest levels of sulfur dioxide ever measured at the volcano. The island was swamped by such high levels of the gas that Hawaii County’s Civil Defense issued island-wide air quality warnings.

Such high levels are “something that we don’t often see,” Kern says. Volcanic smog, also called vog, is a gaseous mixture composed mostly of water vapor, sulfur dioxide and carbon dioxide. One of many hazards associated with volcanic eruptions, the emission of sulfur dioxide can irritate the skin and eyes and, if inhaled, choke airways (SN: 7/7/18, p. 32).

In some instances, as much as 100 to 200 kilotons of the gas were released per day. Before the heightened activity, Kilauea emitted roughly five kilotons of sulfur dioxide daily, mostly through the summit crater’s lava lake.

Now, Kilauea appears to be in a hiatus. It’s producing much less sulfur dioxide, about 35 tons per day, and seismic activity has plummeted. There hasn’t been much land movement, save for swelling around the East Rift Zone’s Puu Oo vent, which indicates that magma could still be creeping deep below. Nobody expects the volcano to stay quiet forever, Neal says. “We’re in this lull, and we just don’t know what is going to happen next.”