27-Fire: Mixing (volcanic) fire and water

When the Halema‘uma‘u crater at the summit of Kīlauea Volcano began filling with water in 2019 it wasn’t unprecedented, volcanic crater lakes aren’t uncommon; but, it was surprising for active volcano that hadn’t seen any water at the summit in at least 200 years. The lake had a short lifespan, boiling away in the next eruption, but it helped geologists learn more about how water moves around in the hot rock of volcanic settings. From the summit of Kilauea to Lake Taupo, one of the largest crater lakes in the world, this episode will explore what happens when fire and water mix. 

This episode was produced by Avery Shinneman and mixed by Collin Warren. Illustration by Jace Steiner.


Shane Hanlon:              00:00                Hi, Vicky.

Vicky Thompson:           00:00                Hi, Shane.

Shane Hanlon:              00:02                What do you think of when I say opposites attract? The caveat on this was I was going to try to get this to not be about relationships, because we’ve recently talked about relationships. And in my personal experience, that never worked out for me. But relationship or otherwise. Opposites attract. What comes to mind?

Vicky Thompson:           00:30                Well, your relationships … I feel like you have to have tolerance for opposites.

Shane Hanlon:              00:34                We’re not talking about me.

Vicky Thompson:           00:35                We’re not talking about you. Okay.

Shane Hanlon:              00:38                No. Go ahead. Tolerance for opposites. Okay.

Vicky Thompson:           00:41                Brian and I are very different. Or were very different, actually.

Shane Hanlon:              00:45                Okay.

Vicky Thompson:           00:46                I feel like we’ve grown more the same over 20 years. But when we were in college, when we first started really dating, we were walking to a restaurant once and a surveyor stopped us on the street. They were doing like … I forget what the survey was even about.

Shane Hanlon:              01:02                Like asking questionnaires?

Vicky Thompson:           01:02                Yeah. They started asking. They said, “We could do you both at once,” and started doing this survey. Brian and I literally answered the opposite to every single question. Literally. The guy was looking at us like, “Where are you going with this? Where do you think you’re going with your lives together?”

Shane Hanlon:              01:24                How long were you together by that point?

Vicky Thompson:           01:27                Officially? Maybe a year.

Shane Hanlon:              01:28                I mean, still …

Vicky Thompson:           01:29                Or less than a year, but on and off for longer. But I feel like we both saw it in the man’s eyes that he was just like, “Okay. Well, we’ll see where this is going.”

Shane Hanlon:              01:41                Did you all question anything at that point? Or you just thought, “This is dumb.”

Vicky Thompson:           01:46                No. Because we were young. We were like, “Politics? We don’t have to have the same politics.” And then, we just argued with each other for 20 years until we basically met in the middle, I feel.

Shane Hanlon:              01:59                There you go.

Vicky Thompson:           02:00                Yeah.

Shane Hanlon:              02:03                Not quite so incompatible as it would seem.

Vicky Thompson:           02:05                No. No.

Shane Hanlon:              02:10                Science is fascinating, but don’t just take my word for it. Join us as we hear stories from scientists, for everyone. I’m Shane Hanlon.

Vicky Thompson:           02:19                And I’m Vicky Thompson.

Shane Hanlon:              02:21                And this is Third Pod from the Sun. All right. Today, we’re talking about two incompatible elements of fire and water. To tell us more, I’m going to bring in producer Avery Shinneman. Hi, Avery.

Avery Shinneman:         02:38                Hi, Shane.

Shane Hanlon:              02:40                Okay. Paint this picture for us.

Avery Shinneman:         02:43                I recently made a short-term move to Taupo, New Zealand. There’s this incredible lake here, Lake Taupo. It’s just this massive lake sitting in an active volcanic caldera. So much of the landscape here that I’m learning about is evidence of interaction between the two. Kind of between fire and water. It got me thinking about it and I wanted to learn more.

                                    03:04                Today, we’re going to hear from two scientists who mainly study volcanoes. Both also have something to say about how water in these volcanic environments can make things a little bit interesting. First, we talk to Jim Kauahikaua in Hawaii, who had a front seat to the exchange between lava and water at the summit of Kilauea a few years back.

Vicky Thompson:           03:22                Great. Let’s get into it.

Jim Kauahikaua:            03:29                My name is Jim Kauahikaua and I was born and raised in Hawaii. Currently, I’m a research scientist at the US Geological Survey stationed at the Hawaiian Volcano Observatory. Our mission is monitoring the action of volcanoes in the state of Hawaii.

Avery Shinneman:         03:51                What got you interested in volcanoes?

Jim Kauahikaua:            03:54                I got interested in volcanoes while I was growing up on Oahu, which is an island about 200 miles away. There were frequent eruptions on the island of Hawaii where I live now. Many times, when lava would go into the ocean, it would produce pumice-like particles that would float to the other islands. And so, we would go out of the beach and pick up these little pumice pieces from the eruptions. So I got interested in the volcanoes at an early age.

Shane Hanlon:              04:30                I know that Hawaii is a unique place because it’s in the Pacific, but it’s not part of the volcanic Ring of Fire.

Avery Shinneman:         04:39                Right. Instead, Hawaii is on a hotspot. A place where the earth’s crust is being heated up directly from the hot mantle below. It creates a string of active volcanoes as plate tectonics move the crust over that hotspot.

Vicky Thompson:           04:51                Kilauea is the Hawaiian volcano currently erupting, right? Small eruptions mostly, but all kinds of really interesting things going on there.

Avery Shinneman:         05:00                In any landscape, what I’m most interested in are the lakes. But it turns out that the most notable lakes in Hawaii are not full of water, but lava. Kilauea has been topped by a large lava lake for most of the last couple of decades.

Jim Kauahikaua:            05:14                Lava lakes generally form in craters, so the receptacle is already formed, and then the lava gets deposited in there. The lava lake that we had between 2008 and 2018 was rather unique, in that it was very active and it was small. The lava is very hot, of course. When lava flows, the lava will start to cool on its outside once it gets exposed to air.

                                    05:45                But this lake was small enough and active enough that it never crusted over. It was always active. It was always bubbling and venting gas and things. But it formed by what’s called in geology, “Stoping.” It means that it kind of melted its way up from below into a crater, and then opened up a hole on one side of the crater and the lake was just sitting there. Through its 10 years, it pulled off parts of its rim to get bigger and bigger, but it was never really that big. Maybe a couple hundred yards across.

Avery Shinneman:         06:26                That seems like a fairly big lake of lava to me, but maybe that’s small?

Jim Kauahikaua:            06:30                The biggest one that I can remember was probably about a mile across or something. But the lava level in the lake fluctuates. And so, as the lava level drops, it might form two or three separate lakes. But then, when it rises, it all becomes one lake again. Typical behavior of the Kilauea volcano is that lava is … Or not lava. Magma is stored beneath the summit area somewhere. Probably, not very deep. Maybe three to five kilometers deep or so.

                                    07:08                At times, that reservoir or reservoirs get pressurized, and they will push lava up towards the surface, which is what happened in 2008. The lava lake started. It got pushed up in a very narrow dike or so up to the surface. But when the whole system gets pressurized, it very often pushes out into radial rift zones. And so, in 2019, because the summit had already adapted to having a lava lake up in the summit, that eruption was kind of sealing that part off.

                                    07:48                By the time all this stuff started to try to balance out, the magma that was underneath the summit pushed out all the way past the wall into this lower East Rift Zone. When all that was over, when the smoke cleared and everything, there was a big pit in the summit crater, the summit caldera, that was deeper than the Empire State Building is tall. Even if you consider the antenna on top, that King Kong hung off of.

Avery Shinneman:         08:21                That’s a good reference point. I like that.

Jim Kauahikaua:            08:23                It was very deep.

Shane Hanlon:              08:30                Now, there’s a big crater that used to be a lava lake, but now the lava has disappeared.

Avery Shinneman:         08:36                Exactly. So the big question … There’s groundwater. There’s rainfall. I asked Jim, “What’s going to fill in that space first? Lava or water?”

Jim Kauahikaua:            08:46                Yes. In fact, that was one of our main worries early on. We knew from geophysical studies that there was a shallow water table underneath the summit. It always interested me how all these eruptions could come right up to the surface through that water table without creating explosions or big things like that.

                                    09:06                And so, the folks in charge in the 2018 timeframe were trying to do some modeling to see why that happened, how that could happen, and whether once the magma, the real hot stuff was withdrawn, how fast it would be for the water to come back into the conduit area. The area beneath that lava lake.

Avery Shinneman:         09:33                That’s the big concern? That when the water flows into a space where the lava already is, that you get an explosive reaction?

Jim Kauahikaua:            09:39                Yes. Some previous geological studies have shown that the one big eruption under Kilauea that killed at least 80 to several hundred people happened in 1790. The main mechanism interpreted for the eruption was a mixture of water and magma under pressure, so that when it couldn’t expand farther, it would blast up rocks and gas and such. And so, we were really worried that that was going to be a repeat scenario, but it did not seem to be the case based on modern modeling and modern thought.

                                    10:22                Then, the concern became more of a research concern. We’ve got this hole. There is a research well one mile to the south of this deep hole that is showing water in it at a depth shallower than the bottom of this hole. How long is it going to take for water to come back into the hole? We didn’t want it to come back too fast, obviously. But how long will that happen?

Avery Shinneman:         10:49                How long did it take for it to actually fill into something you might have called a lake? Where the water was persistent in getting deeper?

Jim Kauahikaua:            10:57                The hole remained empty for about a year. A little less than a year. And so, the water showed up in the very deepest part. It filled rather slowly. And so, it kept filling until December of 2020. At that point, it was 50 meters deep. Not a lot of water. The water itself was fairly hot. 70 to 85 degrees C.

Avery Shinneman:         11:23                Was it otherwise what we might think of as a typical small lake?

Jim Kauahikaua:            11:28                It wasn’t fresh water.

Avery Shinneman:         11:29                Ah.

Jim Kauahikaua:            11:30                It was fairly strongly hydrothermally altered. It was saturated with calcium sulfate, which we suspected. Because when the 2008 lava lake finally made it up to the surface, it blasted out some rocks to open the crater itself. Those rocks … Many times they were covered with a mineral that comes out of calcium sulfate. But it was kind of weird water. It was dark. We couldn’t see through it. It wasn’t clear. It had a pH of four. Not too bad.

Avery Shinneman:         12:11                For a volcano lake, anyway.

Jim Kauahikaua:            12:14                Yeah.

Avery Shinneman:         12:15                Was there any microbial activity? Was there anything living in there? Or was it just …

Jim Kauahikaua:            12:20                We never got the chance. Our university colleagues were eager to get that kind of a sample, but they were requiring procedures that we were not ready to do. In our UAS work, to do that kind of sampling, everything had to be sterile going into the lake. We just were not prepared to do that.

Avery Shinneman:         12:44                How long in the end did the water last? How long did it take to drain out when it left again? Because now we’re back to a state where it’s at a lava lake again. Correct?

Jim Kauahikaua:            12:52                I think it was something like 14 months there was water in there. And then, when the current eruption happened, of course all that water boiled off. Because the eruption happened within the lake itself as well.

Avery Shinneman:         13:05                After taking more than a year to fill, the lake just boiled away. Just like that? It must have been pretty dramatic.

Jim Kauahikaua:            13:12                It was quite vigorous. Having magma or lava directly connected to the water, especially in a water lake … It was a very explosive interaction, which we’ve seen before when lava flows go into the ocean, but it did not build under pressure. There was no containment of it. And so, it was just kind of boiling off. It did generate a steam plume, and it was about 14 kilometers high, but it only took 90 minutes to boil all that water off and produce this 14-kilometer high plume.

Avery Shinneman:         13:48                Wow.

Jim Kauahikaua:            13:49                It was very dramatic.

Avery Shinneman:         13:51                Is there anything you learned from watching this eruption? For example, the minerals that were coming out in the groundwater that might help you identify it in the past now? Could you look for this in the rocks, knowing what you know now about what happened?

Jim Kauahikaua:            14:06                You would hope that would be the case, but no. Because it was anhydrite mineralization that occurred on the rocks and the 2008 stuff, it’s highly dissolvable. Anything that was left around would’ve been washed out by rain in a few years.

Avery Shinneman:         14:24                This may have happened many times before, but we wouldn’t know it from what we see now at the volcano?

Jim Kauahikaua:            14:31                Well, we don’t have any evidence of it happening in the last 200 years, but yes. It could have happened before that. The only record we have of that is Hawaiian chants and stories. None of them clearly identify the existence of a water lake in the summit. However, I will say that when we got heavy rains in the summit area, there are temporary lakes, little pools that form, but they don’t last more than a few hours.

Avery Shinneman:         15:08                There was ever so briefly a water lake at the summit, but we don’t know much about how it functioned, what may have been living there. Just that it was there. Pretty suddenly, it wasn’t anymore.

Vicky Thompson:           15:19                Watching that pot boil for 90 minutes until it was dry must have been really something.

Avery Shinneman:         15:24                It turns out that in that same eruption there was another lake, Wai O Pele or Green Lake that had a much longer history on the landscape, but even shorter demise than the 90 minutes or so that it took to lose the Kilauea Crater Lake.

Jim Kauahikaua:            15:37                Green Lake. The actual name is Wai O Pele, which means, “Water of Pele.” It’s about 20 feet deep. Six meters deep, really. It’s less than a hectare in area. Or was, I should say. And so, it took 90 minutes for lava to burn off the summit water lake.

                                    16:01                This thing went in a flash, probably seconds, as the whole lava flow went into the lake interior of that crater and took it out. I was in the air at that time. Right around it. I could see the plume come up. By the time we made another round, it was gone.

Avery Shinneman:         16:22                The lava going into the lake was so fast that it was just gone before anyone realized?

Jim Kauahikaua:            16:26                Yep.

Avery Shinneman:         16:27                That’s pretty incredible.

Jim Kauahikaua:            16:29                Except for the steam. A lot of people saw the steam plume.

Avery Shinneman:         16:33                What does it look like now? Is there evidence? Did the lava fill in a way that you can see an impression of a lake basin? Or is it just gone?

Jim Kauahikaua:            16:44                The Wai O Pele water lake got filled with the first lava flow that went through there, but there were several after it. And so, all you see now is evidence of that last set of flows around the crater that it was in. You have no sense of where the lake was.

Avery Shinneman:         17:02                If you imagine being a geologist a thousand years from now and the rocks have eroded away … Do you imagine there’d be lake sediment still in there that you could see any evidence at all? Or is the lake utterly gone?

Jim Kauahikaua:            17:14                Probably, if you drilled through the lava flow, you would find that sediment. There was certainly a lot of sediment. Because the sediment is still there. Of course, it’s baked now, so it might be a bit hard. You’d really have to look and have to know where it was before you’d even invest in the drilling to get there.

Avery Shinneman:         17:36                Sure. I’m imagining someone puzzling out one fish fossil deep in a lava flow with some future geology course.

Jim Kauahikaua:            17:44                Yeah.

Shane Hanlon:              17:54                All right. Lakes can evaporate in a flash in lava flows that erase them from the landscape. Do we know anything about how this will continue into the future?

Avery Shinneman:         18:05                I asked Jim about that. What they’re looking for in future research. As the volcano changes over time, and the flow of magma and the flow of lava changes … I imagine that would also change where the groundwater is able to go?

Jim Kauahikaua:            18:23                Yes. It’ll change the subsurface structures that now confine water into certain areas, but it will also build up new ones. When I first started working for the survey, I was interested in answering that question about how eruptions could come up from depths through the water-saturated rock. Probably, a kilometer or more of water-saturated rock.

                                    18:47                You would never know. There’s no explosions or earthquakes or anything that are related to that interaction. The best that we can come up with so far is that, as it’s coming up, it’s slowly sealed its way up there. So that only small amounts of water are really interacting with the hot temperatures.

Avery Shinneman:         19:07                Do you have a hypothesis about what it is that’s holding the water up at the summit?

Jim Kauahikaua:            19:11                Well, we think it’s the same mechanism. The sealing off of normal ways that water would flow back out to the ocean. In the summit, there have also been the number of explosive eruptions. And so, there’s probably layers of ash, which is very fine. It would probably make almost a clay layer in there. There might be water that finds it difficult to go down, because it can’t go through these layers. And it can’t go sideways because of the structure of the caldera. So it could just be sitting there.

Avery Shinneman:         19:46                That’s really interesting.

Shane Hanlon:              19:53                The way I see it, in Hawaii, I have this feeling that the fire is kind of winning. These small lakes form, but are really ephemeral.

Vicky Thompson:           20:04                Losing a whole lake in seconds is pretty wild.

Avery Shinneman:         20:07                I’m actually in New Zealand right now. I moved here for a bit. I talked to someone here about a pretty different kind of caldera lake.

Shane Hanlon:              20:15                Watch out. It might not be there in a whole 90 minutes.

Avery Shinneman:         20:18                Well, this lake is a whole lot bigger. The eruptions here are pretty different as well.

Finn Illsley-Ke…:            20:28                My name is Finn Illsley-Kemp. I’m a research fellow at Victoria University of Wellington in New Zealand. I moved here as part of a large research project, which was looking into the caldera volcanoes in New Zealand, and was aiming to better understand them and better prepare New Zealand for any future unrest or possible eruptions from those volcanoes.

Avery Shinneman:         20:52                For a starter, just for the podcast audience … Could you give us a two-minute overview of why we’re in such a volcanically-active region in New Zealand? What’s happening here that’s setting the stage for all these volcanoes and calderas?

Finn Illsley-Ke…:            21:09                New Zealand is part of what’s often called the Pacific Ring of Fire. The volcanism and also a lot of the earthquakes we have here in New Zealand are primarily driven by subduction. In New Zealand, essentially the whole country is on the plate boundary between the Pacific Plate to the east and the Australian Plate to the west. In the North Island of New Zealand, this manifests as a subduction zone. We have the Oceanic Pacific Plate to the east is subducting beneath the continental Australian Plate to the west.

                                    21:44                This subduction, through typical processes of subduction, transports water and volatiles down into the mantle beneath the North Island. That in turn drives the production of melt and volcanism at the surface. In the North Island, we actually have distributed volcanism in the North Island. It’s quite an amazing area. As a newcomer here, and certainly if you don’t have a detailed knowledge of caldera volcanoes, I think your eye is primarily drawn to the mountains.

                                    22:17                We have the andesite volcanoes, such as Ruapehu and Tongariro, which are to the south of Taupo. Those are quite typical volcanoes that we get at subduction zones. They’re beautiful volcanoes. They’re very big mountains which stand out in the landscape. And so, those really catch your eye, firstly. Also, especially in Taupo, but also to the north in Rotorua, there’s an awful lot of geothermal activity in this area.

                                    22:48                Driving around, you can see the steam coming up from the ground. You can also see there is lots of … I was very taken by the amount of geothermal power plants, which have these huge steam plumes coming from the cooling towers. I think that’s really what catches your eye initially. And then, in Taupo, you have this huge lake, which is really enormous. It’s beautiful, but I think for many people first seeing it, they don’t realize that itself is a volcano.

Shane Hanlon:              23:24                So no lava lakes here?

Avery Shinneman:         23:27                Nope. Things are pretty different in this scenario. Not only are there no lava lakes, the magma underneath the surface is barely mobile.

Finn Illsley-Ke…:            23:38                We think that the reservoir probably spends most of its life with about 30% melt within it. It sits there. It’s still active, it’s still alive. But in that state, we think that it can’t erupt. It’s too immobile to actually erupt in that state.

                                    23:55                And so, what happens prior to an eruption … For reasons we don’t understand particularly well, from that very large 30% melt body, the melt is extracted into a shallower, essentially pure melt system. It’s that, what we call a melt lens, which actually erupts. And so, that’s a really important consideration with Taupo. It’s a necessary precondition. That melt has to be brought out of the mush, in order for it to erupt.

Avery Shinneman:         24:32                We don’t really know much about why that happens. Is that part of what you’re trying to monitor with figuring out some tools to look at what’s happening under there?

Finn Illsley-Ke…:            24:42                Yeah. It’s a very difficult question, because we don’t truly understand exactly what is the trigger for that happening. It also is important to know that even if it does happen, even if that melt is extracted, it doesn’t necessarily erupt. It could then just go back into the mush state. That’s a real difficulty when we’re trying to monitor these volcanoes. We don’t have many examples to point to and say, “This looks like that.” Because it just hasn’t been seen.

Avery Shinneman:         25:12                How interesting. One of the big challenges then that you were working on in the paper that I came across and was looking at is that Taupo is maybe a somewhat unusual case of a volcano that’s still quite active, but has this massive caldera lake.

                                    25:28                There are other examples of large hotspots or other large-scale continental volcanoes with big calderas, but they’re not full of water. Yellowstone is what comes to mind. What is the depth of Lake Taupo? I don’t actually know that off the top of my head.

Finn Illsley-Ke…:            25:44                The maximum depth is about 200 meters, but on average it’s about 100.

Avery Shinneman:         25:47                Okay. You’re trying to look through 100 or 200 meters of water to be able to instrument what’s actually happening at the volcano. Can you talk a little bit about what the challenges of that were?

Finn Illsley-Ke…:            25:59                It certainly poses a challenge at Taupo. And it’s quite different. The Caldera is completely submerged by the lake. You’re right. At Yellowstone, for example, there are lakes, but it doesn’t cover the whole caldera. With Taupo, the lake is a very large barrier to monitoring. We currently don’t have any monitoring equipment on the lake floor. I think it’s important there to give a little bit of background to the history of Taupo, and some things which are quite particular to the culture in New Zealand.

                                    26:35                The Iwi, which is the tribe of the indigenous Maori in New Zealand … Around the Taupo area, that Iwi is called Ngāti Tūwharetoa. They have a long, long history of a deep connection with the volcanic landscape. Particularly, with Tongariro, the volcano to the south, but also with Lake Taupo. As part of their reparations with the New Zealand government and the Crown, they legally own the lake and the lake bed.

                                    27:10                And so, they are guardians of the lake and do a fantastic job in protecting the water quality of the lake and have any say about anything that happens there. But that process has not been without challenges. Relationships between Iwi and the Crown are very difficult and have a lot of painful histories. Any observations that we would want to do on the lake floor would have to be in collaboration with Ngāti Tūwharetoa. And that’s something that they’re keen to do as well.

Avery Shinneman:         27:44                Some of what you’ve been monitoring in the meantime instead is about watching the lake level change. Instead of being able to watch at the lake bed, watching the impact on lake level at the surface. Correct?

Finn Illsley-Ke…:            27:55                That’s right. That was a really cool study that we published this year. That was working with a guy called Peter Otway, who was a former surveyor at GNS Science, which is the geological survey of New Zealand. He lived in Taupo. Back in 1979, he developed a novel surveying technique that was using the lake water as a reference level. What he did is, around the edge of the lake, he would find a solid piece of rock and would fasten a measuring device into the rock and then dangle a kind of pendulum down into the water.

                                    28:35                And so, the idea is that, then if you correct for changes in the lake water itself … If the rock was to move up, then relative to that, the lake would go down. You can detect changes in the ground movement itself in a vertical sense by measuring changes in the relative water level. And so, he set up these measuring stations all around the lake back in 1979. He’s been taking these measurements at least four times a year, every year since. We have over 40 years of data.

                                    29:13                And so, it was really fun. He actually sent me a letter in the first COVID-19 lockdown we had here in New Zealand. Since then, for the last couple of years, me, Peter, and another researcher here, Eleanor Mestel, we’ve been digitizing that data set and then looking at them as a time series. It’s really fantastic. Because what’s really unique about this data set, and it has so much value … The 42 years of data that it represents goes beyond our records of more modern instrumentation like GPS.

Shane Hanlon:              29:56                I volunteer to do the part about going out in a boat in beautiful weather.

Avery Shinneman:         30:02                I know, right? It would be a really great way to understand the landscape and a pretty good day.

Shane Hanlon:              30:08                Is this similar to the eruptions we were talking about in Hawaii?

Avery Shinneman:         30:13                Well, it’s different in a lot of ways that we’ve heard about.

Vicky Thompson:           30:16                But are heat and water still part of the equation?

Avery Shinneman:         30:19                Is there any primary hazard in the direct path of the eruption as it’s starting to happen? I spoke in the other part of this podcast to someone in Hawaii. Looking at the phreatic eruptions that happen when the lava comes in contact with water. It’s a very different eruptive style here. But what would be the primary hazard of having that eruption take place into this massive volume of water potentially?

Finn Illsley-Ke…:            30:45                The interaction between that water and magma would tend to make the eruption more explosive. Certainly, in the early stages. We do see that when we look at the deposits from past eruptions … For example, the last eruption from Taupo was about 1,800 years ago. That eruption had multiple sequences in it. And if you go into the field and look at the deposits from that, you can see that some of the early stages have been altered by water interaction. That would change the explosivity.

                                    31:18                We actually see from that eruption, it was so huge that it seems that later on in the eruption we see no interaction with water, which suggests that either the water was completely thrown out or evaporated … Or that the eruption was powerful enough that it was pushing the water aside, and the magma was coming to the surface with no water interaction at all.

Avery Shinneman:         31:52                There’s also just so much more water here though. Unlike Hawaii, the water is going to stick around and potentially lead to some other hazards.

Vicky Thompson:           32:01                If it’s not boiling off, where is all that water going to go in an eruption?

Avery Shinneman:         32:06                Is there evidence in the rock record around the region of places that there’s been catastrophic dam breaches or building of dams? That kind of rapid landscape alteration that you’re talking about when the outlets of the lake are changed? That might appear in the rock record.

Finn Illsley-Ke…:            32:23                Absolutely. It’s really interesting. In Taupo’s recent eruptive history, there’s been two very large eruptions. There was the Oruanui supereruption, which was about 26,000 years ago, and the Taupo eruption, which was in 232 AD. About 1,800 years ago. In both of those, we see that the amount of material ejected was so much that it dammed up the outlet at the Waikato river.

                                    32:58                For example, the Taupo eruption 1800 years ago, we see that the river was dammed and the water level of the lake rose by several meters. We think it was in that state for approximately a decade at this heightened lake level. And then, the temporary dam that had been formed burst and there was a catastrophic flood down the Waikato River, which actually changed the course of the river. If you look in landscapes to the north of Taupo, you can see the former direction of that river.

                                    33:36                And it’s really interesting, because if you look around Taupo … You’d be able to do this probably out your front door, Avery. You can see, if you look around the lake, there’s a terrace around the side of the lake. And then, Taupo town, the front of the town is on a terrace. That terrace is the beach that was formed during that decade, when the lake level was at its higher point.

Shane Hanlon:              34:06                It seems like water creates a lot of complications.

Avery Shinneman:         34:10                Volcanic eruptions are already a bit of a complication in life.

Vicky Thompson:           34:15                True. But it also seems like there are some really cool ways that the lake is helping us to understand the volcano and its history.

Avery Shinneman:         34:22                For sure. There are even more considerations here though, because the lake is such a significant landscape feature. It’s not really just the eruption itself that can cause complicated impacts.

Finn Illsley-Ke…:            34:33                I think another challenge that the lake poses is that … Because it’s such a huge body of fresh water, from that and from development, it has increased the potential exposure of New Zealand to any future activity. Firstly, just the fresh water itself is a major supply of drinking water for New Zealand. All the way up to major cities like Hamilton still source their drinking water from Lake Taupo.

                                    35:04                If there was any volcanic activity then that was large enough to affect the water quality, that could be a real problem. Also, Lake Taupo has one outlet, which is the Waikato River. Along that … I don’t know how many, but there is multiple hydroelectric dams along the Waikato River, which again is a major proportion of New Zealand’s electricity generation. It comes from this area.

                                    35:33                And so, that would obviously bring hazards. Potential flooding hazards, if there’s some catastrophic failure of a dam. But also, energy security in New Zealand could be really affected by even a relatively small eruption at Taupo. Naturally, when people think of an eruption, particularly from Taupo, people think about ash falling on them or lava or pyroclastic flows.

                                    35:55                Those are terrible and could pose a really great hazard, but it’s also these more subtle secondary impacts from an eruption that could actually have a longer-lasting impact. You can see 25,000 years of history of this volcano right in front of you. You can touch it. I think that’s a really amazing part of this landscape.

Vicky Thompson:           36:29                So many things happening in this landscape.

Shane Hanlon:              36:33                I said previously that it seemed like fire is winning, but with so much water in the landscape … Actually, I’m not sure who’s winning between these two.

Avery Shinneman:         36:42                I don’t know. There’s a lot going on with both of them in this landscape. But being that I’m in Taupo right now and looking out on this huge beautiful lake, I am just really happy to learn that at least the super volcano is not on its way anytime soon.

Shane Hanlon:              36:56                Yay for no super volcanoes. At least, in this current moment.

Avery Shinneman:         37:01                In this current moment.

Shane Hanlon:              37:04                Right. Well, I would like that as a positive way to end. With that …

Avery Shinneman:         37:10                I’m probably not going to blow up soon, so that’s key.

Shane Hanlon:              37:15                Right. Well, that’s all from Third Pod from the Sun.

Vicky Thompson:           37:18                Thanks so much, Avery, for bringing us this story, and to Jim and Finn for sharing their work with us.

Shane Hanlon:              37:24                This episode was produced by Avery and me with audio engineering from Colin Warren. Artwork by Jay Steiner.

Vicky Thompson:           37:31                We’d love to hear your thoughts on the podcast. Please rate and review us. You can find new episodes on your favorite podcasting app or at thirdpodfromthesun.com.

Shane Hanlon:              37:40                Thanks, all. We’ll see you next week.

Vicky Thompson:           37:47                Are you from Chicago? Or that area?

Avery Shinneman:         37:53                I’m from Minneapolis.

Vicky Thompson:           37:53                Okay. Okay.

Avery Shinneman:         37:54                But it’s weird. Because it’s like a song about a massive fire starting and running away from these fatal flames.

Vicky Thompson:           38:00                Yeah.

Avery Shinneman:         38:01                Did you sing the Titanic song? Maybe this is like …

Shane Hanlon:              38:05                The Titanic? Oh my god.

Vicky Thompson:           38:05                No.

Shane Hanlon:              38:05                I have so many questions.

Avery Shinneman:         38:06                “They built the ship Titanic, to sail the ocean blue, and they thought they had a ship that the water wouldn’t go through.”

Shane Hanlon:              38:14                This is amazing.

Vicky Thompson:           38:15                And then, they drowned.

Avery Shinneman:         38:16                “But the good Lord raised his hand and said, “This ship will never land.” It was sad when the big boat went down. Glug. Glug. Glug.” This is the kind of stuff we sang at daycare. Now, I’m having really big feelings about my childhood all of a sudden. My lord.

Shane Hanlon:              38:30                This is so amazing.


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