Hawaii’s Newest Eruption Makes Volcanologists Nervous

May 6, 2018

“There’s not a lot of words to capture a gradual, slow-developing disaster like this.”

An ordinary American neighborhood has been evacuated … because of a volcano.

On Thursday evening, Hawaii County ordered roughly 1,500 people near Pahoa, Hawaii, to leave their homes. The cause: A new lava fissure opened on Kilauea, a massive volcano in the southeast of the state’s Big Island. Lava from the fissure has come within several hundred yards of homes, threatening two subdivisions in the area. The fissure is also releasing toxic amounts of sulfur dioxide, according to Hawaii News Now.

A ponderous lava flow, moving through trees: It’s not exactly the sudden explosion that many Americans imagine when they hear the words volcanic eruption. But for exactly that reason, “it’s the kind of eruption that makes volcanologists nervous,” says Erik Klemetti, a volcanologist at Denison University.

Right now, the U.S. Geological Survey is still trying to understand the new fissure. If the lava flow stabilizes, residents could return to unharmed homes in a week or two. But if the new fissure follows a pattern set by other fissures on Kilauea, then the evacuation could “last for a prolonged period of time,” says Klemetti.

And “because it tends to fall out of public view, it can have a long-term impact on the communities,” he says. It’s happened several times before.

Kilauea is “unlike a lot of volcanoes because it’s a shield volcano”—meaning it has long, sloping sides—“and because it’s huge,” Klemetti says. “The scale of it is hard to comprehend until you’re on the volcano and you realize you can drive 20 miles and still be on the volcano.”

Kilauea has also “been pretty much in eruption for the last 35 years,” he adds. There are long-simmering lava lakes within its crater, and every so often new flows appear within Volcanoes National Park. But the new fissure has appeared much farther down the face of the volcano, in an area where there hasn’t been an eruption since the 1950s. In that time, trees and wildlife in the area have largely recovered. And developers have constructed at least two subdivisions nearby, called Leilani Estates and Lanipuna Gardens. Authorities ordered residents to evacuate both of them on Thursday.

Even if the eruptions of the last century were destructive, they haven’t been sudden or violent. Mika McKinnon, a geophysicist and disaster researcher, says that Kilauea does not suddenly explode like Mount St. Helens did in 1980. This has to do with where and why the volcanoes formed on the Earth—and also with the chemistry of the Earth’s tectonic plates, those great, drifting chunks of rock that form the surface of the world.

There are two types of tectonic plates: oceanic and continental. Oceanic plates are denser than continental plates, and don’t contain very many granitelike rocks, such as quartz or silica. When an oceanic plate melts—which is what’s happening now at Kilauea—it tends to form lava that is very runny. This type of lava can get very hot, but it’s so liquid-like that any gas just bubbles out of it. “It creates more gentle eruptions and these beautiful, dome-shaped volcanoes,” says McKinnon.

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