Hawaii’s 2 volcanic eruptions keep spewing lava with no end in sight. Here’s what could happen next

By Holly Yan, CNN

The incessant lava shooting out of Hawaii’s Mauna Loa and Kilauea volcanoes has stirred memories of Kilauea’s devastating 2018 eruption, which swallowed hundreds of homes.

But the current eruptions are different. While it’s unclear how far the lava will travel from either volcano, experts say history and context can provide clues.

Why Mauna Loa’s lava is harder to predict

Mauna Loa is the world’s largest active volcano. It stretches 10.5 miles from base to summit and takes up half the entire surface area of Hawaii’s Big Island, the US Geological Survey says.

But compared to its smaller neighbor Kilauea, Mauna Loa doesn’t erupt as frequently. So there’s not as much historical data on its lava and where it travels, said Tracy Gregg, associate professor of geology at the University at Buffalo.

And that makes the trajectory of its lava — which can change at any moment — harder to predict.

“But the good news about lava is that — particularly on the island of Hawaii — it doesn’t really sneak up on people. Folks know when it’s coming,” Gregg said.

“So in terms of loss of life, I’m not concerned.”

Lava from Mauna Loa was crawling forward Tuesday at about 21 yards per hour, said Mike Zoeller of the US Geological Survey’s Hawaiian Volcano Observatory.

The lava advance, which recently slowed after hitting flatter surfaces, was within 1.92 miles of the Daniel K. Inouye Highway — the major highway connecting the eastern and western halves of Big Island, he said.

But all “that could change in an hour,” Gregg said, making the task of guessing which — if any — infrastructure or buildings could be damaged by lava much more difficult.

It seems unlikely that Mauna Loa’s lava will wipe out homes; the closest major population center is Hilo, about 37 miles northeast.

“In some cases, Mauna Loa flows have traveled as far as Hilo and South Kona, so there certainly might be exposure of communities to lava,” said Einat Lev, an associate research professor in seismology, geology and tectonophysics at Columbia University.

“However, this is very unlikely judging by the length of historical lava flows,” Lev said.

Indeed, “Mauna Loa lava flows have not inundated communities,” Gregg said.

“There have been some scares. Hilo is one of the biggest cities on the island, and in the 1880s, Mauna Loa lava flow kind of crept up pretty close to Hilo — but even then didn’t quite make it.”

Right now, there’s a “small chance that the flow would diverge and turn towards the west,” Lev said, where “it might interact with roads and structures in the Pōhakuloa Game Management Area.”

The US Army’s Pohakuloa Training Area is about 20 miles north of Mauna Loa. An unexploded ordnance was spotted this week in lava rocks near a Mauna Loa eruption viewing area, Hawaii News Now reported.

“Unexploded ordnance may indeed be found in the area, given its long history as a training area” for the Army, Lev said.

But there are too many variables — such as how deep the military device is in the ground — to speculate what might happen if a lava reached it, Gregg said.

Why this Kilauea eruption probably won’t be as devastating

Just 21 miles away from Mauna Loa, Kilauea has been exploding for the past year.

But unlike the 2018 Kilauea eruption that destroyed hundreds of homes in the Leilani Estates neighborhood, the current eruption is much different thanks to where the lava is shooting out from and how close the eruption is to people.

“Lava from the 2021-present eruption has been confined to the summit crater,” Lev said.

In other words, lava isn’t gushing down the side of Kilauea right now. It’s staying near the top.

“This is in contrast to the 2018 eruption, when the eruptive vents were located low on the southeastern flank of the volcano,” Lev said.

“There is always a chance that there will be another eruption on the flank, closer to communities, but not from the current location of the Kilauea eruption.”

Gregg hopes Kilauea’s eruption stays put, with lava shooting up from and staying within the summit crater, she said.

“If you think of the summit crater as like a bathtub, the bathtub is barely even beginning to be filled,” Gregg said.

“Right now, the lava at Kilauea is behaving very nicely. And we hope that lasts.”

Why lava doesn’t like to follow orders

Humans in the past have tried to divert or even stop lava from advancing. Workers have used bulldozers to build huge earthen walls to try to redirect lava after eruptions, such as that of Mount Etna in Sicily.

But “the history is not successful,” said Paul Segall, a professor of geophysics at Stanford University.

In 1935, the founder of the Hawaiian Volcano Observatory asked the US Army Air Corps to bomb the source of lava flowing from Mauna Loa as it headed toward the Wailuku River, according to the US Geological Service.

The army dropped two 600-pound bombs, but they missed their target and had minimal effect on the lava flows.

Lava’s tendency to flow “is extremely temperature-sensitive,” Segall said. That makes it “somewhat unpredictable.”

But with neighboring volcanoes now erupting simultaneously, scientists are eager to study what will happen next.

“It would be fascinating to see if the eruptions influence each other,” Lev said.

No matter what happens, Gregg said, residents and tourists should pay attention to warnings from local officials and heed any guidance from volcanologists.

“I think the most important thing is that we really can’t predict what’s going to happen on an hour-by-hour or even day-by-day basis.”

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CNN’s Zoe Sottile contributed to this report.