Short Wave - What Led To The Massive Volcanic Eruption In Tonga

Episode Date: February 28, 2022

Scientists are piecing together what led up to a massive volcanic eruption in Tonga last month. NPR science correspondent Geoff Brumfiel joins the show to talk about the likely sequence of events— and what it can teach us about future eruptions like this one.Email the show at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

All righty, shortwave, the day that you have all been waiting for, the day I have been waiting for, is finally here. After months of searching, I'm excited to introduce you to our new Shortwave co-host and my buddy in science banter, Aaron Scott. Hi. Hey there, Emily Kwong. Hi. I cannot tell you how delighted I am to be here with you. Erin, we're so excited to have you on the team. Welcome. And, you know, there's going to be many opportunities to get to know you, but I want to start off with one fun fact, which is that you are based on the West Coast, right?

I am indeed. I'm in Portland, Oregon. I've been here on and off since I was a kid because, frankly, it's a hard place to leave. I get it. And you're saying we can't tempt you to NPR headquarters in Washington, D.C. Emily, let's just say that when I hear someone say Washington, I think of the state. It hurts so bad. I made the mistake of leaving the Pacific Northwest once. You're making me regret it right now. What have you been doing out in Oregon? Yeah, so I spent the past seven years working at Oregon Public Broadcasting and getting to really explore some of the cool science that is happening out in this misty corner of the country.

I've gotten to, you know, crawl down into caves looking for spiders that date back to dinosaur days. I've gotten to go bushwhacking and old-growth forests and hooting for spotted owls. And, you know, gotten to climb up some volcanoes with a microbiologist who studies snow algae. Very cool. And speaking of volcanoes, today you're talking to Jeff Brumfield on the science desk about one volcano that has been making headlines. Yes. That's coming up next on Shortwave, the Daily Science Podcasts from NPR. How'd that feel? That feel good.

That felt good? Okay. You're listening to Shortwave from NPR. Today on the show, I've got MPR science correspondent Jeff Brumfield. Hello, Jeff. Hi, Aaron. Nice to meet you. So we're going to be talking about that volcanic eruption in the island nation of Tonga. Devastating, underground.

volcanic eruption off the coast of Tonga over the weekend. Despite the violent explosion, the Tongan government has so far reported just three deaths. It has been termed as one of the most powerful volcanic eruptions of the 21st century. It made quite a few headlines. There were those satellite photos from space showing what looked like an enormous explosion. Satellite images showing a massive cloud of smoke spewing in all directions. the most powerful volcanic activity in at least three decades. And this was absolutely a humanitarian crisis for Tonga.

The United Nations says around 80% of Tongan households were affected by the eruption. And the nation's still recovering from a tsunami and a lot of ash that fell on their islands. The plume of this ash reached over 35 miles high. It was the highest ever recorded by satellites. So today on the show, we're going to take another look at the Tonga. eruption? Why did it happen? How big was it? And what can it tell scientists about future eruptions like this one? You're listening to Shortwave, the Daily Science Podcasts from MPR. All right, Jeff, so where do you want to start? Well, let's just talk for a minute about Tonga itself. It's a nation made up of around

170 islands. In the east are flat coral islands, and that's where the people live. And the soils on these islands are basically made out of volcanic ash that are coming from the volcanoes to the west. So that's Shane Cronin. He's a volcanologist at the University of Auckland and New Zealand, who spent many years studying Tonga's volcanoes. And basically, this cycle of eruptions from oceanic volcanoes has actually made Tonga a sort of regional breadbasket. It can grow crops, which made it a really prosperous nation in the past. So you're saying that instead of being all doom and destruction, these volcanoes are actually supporting life. That's right, yeah.

So how does this volcano, this particular one, fit into all that? Well, this one's known as the Hunger volcano. It's actually a huge underwater volcano about 40 miles north of Tonga's capital island. And in 2015, a section of it burst out of the ocean and created some new land. Wait, wait, so like a whole new island just popping up in the ocean? That's right, that's right. So this lava bridge literally rises up from the sea, and it connects two smaller islands, one called Hungatonga and the other one called Hungahapai. And so they called it Hungatonga Hapai. We could actually land a boat there and get onto the island. So Cronin was one of the first scientists on Earth to reach this new piece of land. And he described it kind of like a moonscape, this barren gray strip that felt really otherworldly.

The horizon is almost unlimited. And the stars that come out on a clear night are, you know, something you've never seen before. It's just spectacular. Jeff, it's giving me shivers just thinking about it. I mean, this must have been what land was like for those very first life forms that emerged billions of years ago. And just trying to imagine that, being that first slimy little critter crawling out of the water and seeing those stars for the very first time. Of course, presuming they had eyes, which they probably didn't.

But at the same time, it is just some rock in an ocean full of rock. So why was everyone interested in this island? You know, the truth is actually new land just doesn't pop up onto the earth all that often. There's a handful of volcanic islands like this that get made all over the world. And there are normally fragile little outposts of ash and pumice. Most of these islands wash away in six months. So that's Jim Garvin. He's the chief scientist at NASA's Goddard Space Flight Center in Maryland.

And these islands have come and gone before in the past, but what makes the era we live in different is that there are satellites and radars and just all sorts of instruments that can be used to see one when it pops up and then study it in real time. And if you're wondering why NASA is interested in this one little volcanic cone in the middle of the Pacific, well, they have their own reasons as well, because it turns out it might provide some clues about other parts of the solar system. There's always been a connection of these kinds of volcanoes to Mars, where short-lived, shallow seas and oceans have been, what should I say, hypothesized, partially proven,

and we see fields of small cones that remind us of hunkatunga higrapai and others in areas like Nepentes and other places on Mars. I love it. So you're saying this somewhat rare little island can teach us something about Mars, which means that people are monitoring it closely, watching it with satellites, and so when then did they start to notice trouble? Well, the current story of the volcano really starts in December of last year, a few weeks before the big eruption. So there's a lot more volcanic activity, eruptions and gas and steam and stuff like that. But there was also something different

happening than what had happened there in the past. The island itself sort of started to radically shift. It produced a whole new island footprint. The plumbing system under the underwater changed. So that giant volcanic cone, which was kind of the main feature of the island, looked like a mountain, it disappears from the north side and this new cone pops up on the south side of the island. And then in January, things really get going. So there's bigger eruptions, explosions that can be heard far away in Tonga's capital. Not that any of that's super unusual. I mean, remember, Tonga is truly a volcanic nation. The locals have heard this stuff for centuries,

but then comes the afternoon of January 15th. Eruption starts at four minutes past five. And this time things get wild. We have a big explosion and an earthquake at about quarter past five. The U.S. Geological Survey puts that earthquake at 5.8 magnitude. It triggers a tsunami warning.

And then, really intriguingly, about 10 minutes later, we have an incredible explosion. So that's what it sounded like on an island in Viji that's over 250 miles away from the volcano. Wow. Wow. I remember that day so clearly, Jeff. Just staring at those satellite photos,

it looked like an enormous bomb had gone off. Do we know how big the explosion was? Well, yeah, I mean, after it had... happened, I did spend some time trying to figure that out. And one of the people I spoke to was the comprehensive test ban treaty organization. So this is a group that monitors for actually nuclear weapons tests all over the world. And they told me this was the biggest thing their network had ever picked up in 20 years or so of operation. Even detectors in Antarctica recorded the signal. Now, other scientists I spoke to, they said this was almost certainly as big or bigger than the

largest nuclear bomb ever tested, and that was the Soviet Union's Sarbomba, which went off in 1961. Oh, my. So volcanoes erupt, Jeff, but do they normally explode like nuclear bombs? No, fortunately, they do not. So how then does a volcano become a bomb? Well, I mean, to be honest with you, these scientists still aren't entirely sure, but Cronin is starting to piece together a theory.

So he works with the Tonga Geological Services, and they've sent him volcanic ash from this eruption. And we're seeking clues in those ash samples, you know, what went on during that explosive eruption period. It turns out the samples are actually yielding some pretty good hints. So first of all, the magma, or the liquid rock inside the volcano, was filled with tiny star-shaped crystals. Now, crystals aren't all that unusual because when magma reaches the surface, it can crissue. crystallize. It can kind of freeze, literally. But what was different here is that these crystals are really, really tiny. And that means the magma was still hot and fresh from deep beneath the earth. And that means... The magma that drove this explosion rose very, very quickly.

Cronin told me it came from miles below the earth in a matter of just minutes. I'm trying to imagine that. Tons of liquid rock moving that fast, and I can't. I mean, I mean, we normally think of like magma is oozing, not flowing like a fire hydrant or shooting like some rocket through the earth. So tell me how does that happen? Yeah, it all comes down to pressure, basically. So if you think of the top of a volcano as a cork on a champagne bottle, the magma's kind of like the bubbly. It's just really dying to burst out. But if we're going with the champagne metaphor, that implies that something popped the course.

That's right. Remember that earthquake that preceded the really big explosion? Mm-hmm. So it turns out Cronin thinks that was actually an undersea landslide where an entire flank of the volcano's rim crashed down onto the ocean floor. That would also explain why we've had some damage, for example, to the undersea cables, east of the volcano. And the landslide might have triggered the tsunami that hit some of the islands as well. And so when that part of the rim fell away, then the magma below shot up?

Exactly. I mean, that's all it took was removing all that weight, holding it down. And then in addition to the magma shooting up, with the rim gone, ocean water starts filtering down into the cracks and crevices of the remaining rock. That actually magnifies the explosion and it makes it even bigger. And the way that works is the rock can, for a short time anyway, it can hold the water. and the steam and the magma together and allow the pressure to build and build until finally it blows. But it's also the way in which

weapons explosions are magnified by compressing the accelerant inside a tight container. So what Cronin is describing is like a volcanic super bomb. Yeah. Which is amazing and also terrifying. It is. It is.

And now the volcanologists have seen it in action, they're really determined to get a better sense of when it can happen and how. Because it turns out these shallow undersea volcanoes are actually pretty common all over the world. So you're telling me there could be many, many more super bombs out there? It's a possibility. Cronin told me there are more volcanoes under the sea than there are on land. The Aleutians, the Japan arc, the Caribbean as well.

You know, there are a series of these places, Indonesia, where there are. where there could be similar types of things. And these underwater volcanoes are just not very well studied. Cronin and Garvin and the other volcanologists I spoke to all hope this eruption would serve as a kind of wake-up call so that people can be better prepared for the next time an undersea volcano does something like this. Jeff, thank you for bringing me this hearty mix of terror and awe

for my very first day on shortwave. Today's episode was produced by Chloe Wine edited by Omina Khan and fact-checked by Catherine Seifer. Patrick Murray was the audio engineer. Giselle Grayson is our senior supervising editor. Andrea Kisick runs the science desk. Edith Chapin is the executive editor and vice president of news. And Nancy Barnes is our senior vice president of news.

You've been listening to Shortwave, the Daily Science Podcast from MPR.