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Hawaii's Kilauea volcano suddenly erupted last week. It's happened before, so why are eruptions so hard for scientists to predict?

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[♪ INTRO ].

Something big is happening in Hawaii. Kilauea, the big island’s friendly neighborhood volcano, is splitting open in unexpected places and launching lava high into the air.

The ground is expanding and contracting all across the island, over a thousand people have had to evacuate, and each day brings scary new surprises and terrifying… but you know, also fun to watch home videos. And it’s natural to wonder if we could’ve predicted any of this ahead of time. Well, there were signs that something was coming.

But volcanoes are complicated, and that means even the experts didn’t know exactly what would happen. Even now, there’s still too much we don’t understand about eruptions to confidently say what’s gonna happen next. Kilauea has been pretty much continuously erupting for more than thirty years, making it among the most active volcanoes in the world.

It’s also one of the best-studied: about sixty seismic stations monitor how the ground changes as lava shifts around, along with GPS stations, radar, and webcams. And around the end of April, that extensive monitoring gave volcanologists a tip that something was up—literally. Kilauea’s biggest lava lake — which is exactly what it sounds like — was so high that it was basically overflowing.

The same pressure that was raising the lake had also lifted ground throughout the island by as much as 20 centimeters and sent lava moving through the rest of the volcano. And it’s a big volcano, so there’s a lot of room for lava to shift around. Even under normal circumstances, Kilauea’s lava is always moving and setting off small earthquakes as it does.

But around the same time the lava lake filled up, those earthquakes started getting bigger and more frequent. And that told volcanologists that things were changing quickly; the lava was moving more than it usually does. Then, over the last weekend in April, the summit lava lake dropped by about 15 meters, and a second lava lake completely drained.

Where that lava went soon became clear, as cracks in the ground called fissures opened up last Thursday in a residential area more than 30 km from the summit. Lava spewed out of the fissures, lighting fires and releasing poisonous gases like sulfur dioxide into the air at alarming rates — right next to people’s homes. And Kilauea was just getting started.

Two big earthquakes came on May 4. The first was a 5.4 on the Richter scale, and an hour later there was a 6.9 that caused landslides on the island. New fissures opened up after the quakes.

And there were more earthquakes over the weekend, and even more fissures—at least a dozen in total have opened — some of which launched their lava 70 meters in the air. Most stopped pretty quickly and none of their lava spread very far, but dozens of homes have still been destroyed by the eruptions. And scientists think there’s more to come.

Between April 30th and May 7th, the summit lava lake dropped a staggering 220 meters, and showed no sign of stopping. And measurements of the ground in the early part of this week—when we filmed this episode—showed that lava was still moving around beneath the big island. This isn’t the first time Kilauea’s erupted so far from the summit.

We might think of volcanoes as a steep cone with a single, explosively erupting spout—like. Mount Saint Helens. But larger, flatter shield volcanoes, like Kilauea, can have networks of lava chambers and often erupt from secondary sites.

And that means the most active spot can shift over time, depending on where rocks are weakest. Still, Kilauea isn’t normally considered that dangerous. Instead of exploding like other volcanoes, it usually oozes, because its lava is low in silicate and hotter than average, which makes it somewhat runny.

That lower viscosity also allows gas bubbles to get squeezed out before enough pressure is built up to drive an explosive eruption. But the situation right now is reminding a lot of people of 1955, when at least 24 different places erupted over a few months. There were also similar patterns of rapid lava movement followed by fissures in 2011, though they weren’t as dramatic as 1955.

So this could be a repeat of 1955 or 2011, or it could all be building up to something much bigger and even more dangerous. A recent study showed that Kilauea has had some violent eruptions in the last few thousand years — eruptions that were much closer to what you see with your typical volcano. So that might be on the horizon.

Or all this drama could end pretty soon, and Kilauea might return to its normal oozy happy self. There’s just too much we don’t know about what’s happening underground, and why volcanoes erupt in the first place, to be more certain. Volcanology involves so many variables interacting at the same time that it’s tough to make predictions — even if we can recognize signs of something happening.

Even our best instruments can’t perfectly map the network of chambers and tunnels the lava is flowing through. And to be able to predict an eruption, scientists would not only need that map, they’d also need to know the lava’s composition, temperature, and what gases are trapped within it. We just don’t know enough about what’s under Kilauea’s hood to predict its behavior.

So when and where the next fissure will open up, and how much lava will come out of it when it does, remains an unanswered question — for now, at least. But every time it erupts, volcanologists learn more about Kilauea. So scientists in Hawaii hope that these sudden outbursts from a normally placid volcano will teach us something about how to better predict eruptions the next time around.

In the meantime—if you’re on the big island, stay safe, and don’t park your cars in front of any lava flows. And for the most up-to-date information, check out the United States Geological Survey’s. Kilauea status updates, local news outlets, or some of the links we’ve included in the description.

Thanks for watching this episode of SciShow, and a special thanks to our President of Space. Matthew Brant! Without our Patreon patrons, we wouldn’t be able to make this show and bring you all of this exciting interesting news to give you more context for the cool things that are happening in the world of science.

So thanks Patreon patrons. [♪ OUTRO ].