Short Wave - The Science Behind Whakaari/White Island's Eruption

Episode Date: December 17, 2019

The volcano of Whakaari or White Island in New Zealand erupted just over a week ago. More than a dozen people were killed, including tourists to the popular attraction. Volcanologist Alison Graettinger explains the science behind this particular eruption, a hydrothermal eruption and why they can be especially difficult to predict. Reach out to the show at [e-mail]. Plus, keep the conversation going with host Maddie Sofia on Twitter — she's @maddie_sofia.See 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

You're listening to Shortwave from NPR. All right, Alison, when did you hear about the eruption? So I actually heard about it. It would have been evening time here. So only within a few hours of the eruption because myself and my students were paying attention to Twitter. And they announced the eruption before it was clear that there were people there. So it was like 2 p.m. local time in New Zealand. and we were aware of it,

and then as we proceeded to try and find out more about the eruption, is when so much more information came out. Alison Grettinger is a volcanologist who specializes in volcanic eruptions that interact with water. That's the type of eruption that occurred in New Zealand last week when the volcano Fakhri or White Island erupted unexpectedly while people were touring the island. As of this recording, 16 people have died, and the police continue to search the island. Well, it was that it erupted was sort of surprising because I assigned my students' volcanoes to babysit with the purpose of them understanding that some volcanoes erupt all the time, some erupt sort of by surprise. So we were just thinking about timing and how, you know, you don't anticipate these things, even if you know a volcano is active.

And then, of course, when we found out people were there, my stomach drops. and I thought about a lot of my colleagues who work in New Zealand and probably how much more intense that feeling was for them and all the uncertainty. So there were a lot of emotions. I've been there myself. So a lot of emotions, yeah. Today on the show, the science behind the fakari eruption.

We'll talk about how scientists try to determine when volcanoes might erupt and whether or not anyone should take the risk of visiting an active volcano. So you've been there. Tell me a little bit of what it, you know, kind of looks like. Describe it to me if you can. Yeah, so I had taken one of the boat tours, and you arrive and you start walking up. It's not a steep terrain, but it is very wild. There's loose rocks, and there's sort of a tromp down bit that changes depending on where it's safe to walk.

And there's lots of little holes and things around the trail and lots of steam vents and fumaroles. So fumaroles are where you get active volcanic gases are coming. coming out from depth, and they can cover things in sulfur. So there's lots of bright colors and textures and crystals, and it is fascinating and very not, you're not at home when you're there. You can tell you've walked into this sort of epic landscape. Gotcha. So let's talk about the specific eruption here.

I think when most people think of volcanoes, they think, you know, like lava spewing out and that kind of stuff. Can you talk to me a little bit about this particular eruption? Yeah, so White Island has what's called a hydrothermal system. So there's hot water moving through it. And so I mentioned all this sulfur and the degassing. So there's a heat source somewhere in there, right? So there's magma at depth and it's hot and it's heating the water above it and the gases are escaping.

So when you make water hot, it can be liquid, but it could also turn into a gas. And you can have some bubbles and some water or you can have larger amounts of gas relative to that. And gas takes it more space than water. So if you have changes in that system, you can build up pressure and that pressure can be released in an explosion because that's really all an explosion is, is a release of pressure. So a lot of eruptions that happen at White Island are related just to this more superficial part, and it doesn't even involve the magma at depth. The magma is providing the heat, but it's being brought up by water cycling through the system. Yeah, I mean, I've heard it kind of described as a volcanic pressure cooker. Do you feel like that's a fair representation of the volcano there?

Yeah, anything that you trap pressure in at some point could fail. And that failure is just the release of energy. And in this case, it involves hot water and sulfur and rocks flying through the air in a tragic way. Yeah. So GeoNet, an organization that tracks volcanic activity in New Zealand, called this eruption kind of small from a global perspective. They said it was also pretty short, just, you know, one or two minutes long. so obviously small and short eruptions can still cause a lot of damage, right? Exactly. So if a volcano is going to do something very large, there tends to be, you have to move more rock to get the magma close to the surface, and that gives us a lot of information in the forms of ground shaking or deformation.

But if you're only releasing a small amount of energy, you have less information. But that's still dangerous because those speeds can still occur. and if you're in proximity to the source, I mean, it doesn't matter how many people are there for it to be too many people when one of these happen. Right, right. So let's talk about the issue of detection, because this island is monitored pretty closely for volcanic activity. Are there any real warning signs for this kind of eruption?

Well, there's always information happening at the volcano. We talk about this hydrothermal system. So we can look for rock shaking, we can look for changes in water chemistry, changes in gas chemistry. And one of the tricky parts of a volcano that's active like White Island is those systems, when they have normal behavior, is already complicated. There's just so much information in it. So when there's a change, that's what we're looking for. And frequently you'll say, okay, the system is changed. This is different than what it's been like for the past few months.

Let's raise the alert level. But that doesn't necessarily give you. you any information that tells you, well, is it going to do this for just a few days? Is it going to do this for a long time? Or is this a sign of something more? But the time element is not there for us the vast majority of these small eruptions. And that makes it difficult to anticipate when things might occur. Yeah. I mean, the New Zealand government definitely has an alert system. And it was actually raised, you know, to level two on a scale from zero to five a couple of weeks before. But, you know, I've been reading about that alert system, and they say an eruption can occur at any alert level.

So I'm kind of confused about, like, how helpful that can really be as far as warning people about eruptions. Sure. So volcanoes can have patterns. And frequently, we see patterns when we look at their behavior in past tense. So when you look back hindsight's 20-20 and all of life, including volcanoes. But that doesn't mean the pattern will be identical every time. So we look for changes. and adjust the alert level to say, well, there's some activity. There's something a bit different or a bit more energetic than we saw before. And volcanoes don't always go one, two, three, four, or five.

They don't care about chronology. They could go one to any level they want or back down. Or one to two to one to two to one to two with no eruption for a long period of time. We would like them to be more communicative in a nice chronological way. But that hasn't been our experience at any volcano on the planet that it's, you know, always doing what we wanted to.

Right. Yeah. I mean, so, I mean, you've been doing this a long time, right? And, and one thing that you've told me is these are really difficult to predict. And this is part of the reason why so many people are doing active research. You know, we've had years and years of looking into how these things act, how we can best predict them. But it seems like we still don't have enough information to be really confident about predictions. Is that fair? Sure. So we could think about like the lifespan of a volcano and how long they've been active.

So White Island, as far as we can tell, has been active for 150,000 years. Wow. And we expect to understand it by having monitored it with these fancy geophysical equipment for only a matter of a few decades. So it's asking a lot to have all the information from just a few years of study because the lifespan is much more extensive. our usual scale. But we have to live in our time scale. We need to be able to function in that. So we use what information we have and we take advantage of every bit of information we can get and hope that the next time we can do better. So, Allison, this active volcano has been a popular New Zealand tourist destination. You visited it as a tourist. Do you think that people should

continue to visit active volcanoes? It's a really difficult question, and it's an interesting one that I've thought about different times of my life in different ways. And I will never make the decision for other people, but it is one that should always be re-asked. So is our understanding to such a level that we can say definitely that that is never acceptable? As an educator, since I work in the university system, and that's what enables me to do my science, I always want opportunity. for people to experience this really cool planet we live on. And how do we do that and keep them safe? I don't think there's a concrete answer.

And safety always needs to be the forefront of any decision-making. So, yeah, that was a non-answer. It was actually a wonderful answer, because I'm asking you an impossible question, which is real, like, kind of a butt-head move. But I think, I think, it's an understandable non-answer, right? Because scientists want people to be interested and engaged and continue to learn about these natural phenomenon. But they also really want them to be safe, too, right? So there's a balance there.

Yeah. Ideally, we would keep everyone safe all the time, but then we would never get into a car. Yeah. Yeah. Allison Grettinger is an assistant professor in the Department of Geosciences at the University of Missouri, Kansas City. Today's episode was produced by Rebecca Ramirez and edited by Viet Le. Emily von fact check this episode. You've been listening to Shortwave from NPR. I'm Maddie Safaya, and we'll see you tomorrow.