SPEAKER_00: The apocalyptic vision of fire bursting from the earth haunts man with the image of all in nature that is beyond his control.
SPEAKER_06: There's something about volcanoes that makes them the superstars of natural disasters. Magma violently forcing its way to the surface and exploiting with terrifying force. The images of the ancient Roman city of Pompeii and its doomed residents encased in volcanic ash and pumice are grim reminders of what happens when a volcano wakes up. You might be surprised to learn that the United States is actually one of the planet's most volcanic places. It's got 161 volcanoes in its 50 states and territories that have been active in the last 12,000 years. That's actually the most in the world. The U.S. West Coast forms one edge of the famous Ring of Fire, which is a semicircle of volcanic activity that runs along a series of faults on the edge of the Pacific Ocean. Roughly 75% of the planet's volcanoes occur in this ring. The best known volcano in the United States is probably Mount St. Helens. I still remember as a kid being freaked out watching its 1980 eruption on the news and the ominous clouds of ash it spewed across huge swaths of North America. But here's the thing. North America has a massive volcano that's practically hidden in plain sight right beneath Yellowstone National Park. And it's not just any volcano. It's a supervolcano.
SPEAKER_07: Yellowstone has actually had three super eruptions that we know of throughout its history. There was one at 1.3 million years ago and then it's had two others, one at 640,000 years ago and then one at 2.1 million years ago and that was the largest of all of its eruptions that it's had. And these were big events. I mean, they were in the thousands of cubic kilometers of material that was released.
SPEAKER_06: That's Maya Wei-Haas. She's a science writer at National Geographic and she's got a PhD in earth science and a deep love for volcanoes.
SPEAKER_07: So Mount St. Helens was a devastating event, but the size of that eruption was much, much smaller. So Mount St. Helens' 1980 eruption was estimated at about 0.25 cubic kilometers of material. And so for reference, the smallest of the eruptions from Yellowstone that's considered a super eruption was 280 cubic kilometers. Holy cow.
SPEAKER_06: So we're talking an order of magnitude. Magnitude.
SPEAKER_07: Yeah.
SPEAKER_06: Yeah. If Yellowstone were to blow up now, how big an event, like how far reaching an impact would that have?
SPEAKER_07: Probably one of the biggest concerns globally would be what's sometimes called a volcanic winter. And we've seen this with actually smaller eruptions in human timescales. It's when you generate so much ash kind of that's pumped into the atmosphere, it kind of can shield the earth from sunlight and you can get a degree or two of cooling, which might not sound like a lot, but that actually can have kind of catastrophic effects really when you're talking about agriculture. And so the impacts around the volcano certainly would not be good, but when we're looking at more of a global affair, it's going to be things like food shortages and crop failures that are going to be a problem.
SPEAKER_06: We've been interested in doing an episode on super volcanoes for a while since one of you, our listeners, asked for it in the comments on Apple podcast. Yeah, we actually read those. And then a few months ago, I saw a news story about a report written by scientists at NASA's jet propulsion laboratory in the California Institute of Technology. Its title, defending human civilization from super volcanic eruptions sounded like the blueprint for a blockbuster disaster movie. Coming soon to a theater near you, rise of the super volcano. But the NASA paper was actually about solutions. It wondered whether we could solve two problems at once by devising a system that taps into the Yellowstone super volcanoes geothermal energy, which could supply much of the country with mostly carbon free electricity. Meanwhile, this process would reduce the heat beneath the surface that could lead to an end times level eruption. Sounds awesome, right? I'm Peter Glynn, editor at large at National Geographic, and you're listening to Overheard, a show where we eavesdrop on the wild conversations we have here at Nat Geo and follow them to the edges of our big, weird, beautiful world. This week, we explore the so-called Yellowstone super volcano. Is it really going to destroy us? Or could it save us with a never-ending supply of relatively clean energy? More after the break. This summer, adventure's never far away with a free one month trial to National Geographic Digital. For starters, there's full access to our online stories with new ones posted every day, plus every Nat Geo issue ever published in our digital archives. There's a whole lot more for subscribers, and you can check it all out for free at natgeo.com slash explore more.
SPEAKER_02: About 1870, a group of Montana citizens with a military escort decided to investigate the Yellowstone country to verify some, what they thought were fibs told by the trappers of water spout in the air. So they spent 30 days going up the Yellowstone River around Lake Yellowstone and back through the geyser country.
SPEAKER_06: It's Conrad Wirth, who was director of the National Park Service, giving a lecture at the National Geographic Society in 1959. And it was a fabulous country.
SPEAKER_02: And as was a custom in those days, they were trying to figure out how they were going to divide this land out between themselves and file a claim on it, in which they felt there would be considerable fortune. However, they turned that down cold and say, no, this land is so great, it must be set aside for all the people.
SPEAKER_06: The natural sounds you hear were collected at Yellowstone by the National Park Service and the Acoustic Atlas at Montana State University. Yellowstone, America's first national park, was established in 1872 on more than 3,400 square miles. It stretches across northwestern Wyoming and parts of Montana and Idaho. It's famous for its abundant wildlife, bison, wolves, bears. But it's also famous for its unique geological features, especially its spectacular geysers, most notably the one called Old Faithful, which shoots huge jets of scalding water into the air just over once an hour. Geysers like this are actually pretty rare. In fact, if you're standing at the Old Faithful Visitor Center, you're practically within sight of half the active geysers in the entire world. These thermal features are the byproduct of a massive volcano hidden beneath the surface. Although, you know, I've been to Yellowstone, I've seen the geysers. Where's the volcano?
SPEAKER_07: So it's not the kind of volcano that you think of in a lot of textbooks. You see these perfect triangular peaks. And those are known as stratovolcanoes. But the Yellowstone itself is actually kind of, they call it a caldera systems.
SPEAKER_06: A caldera system is a type of volcano that undergoes such a large eruption that the surface collapses in on itself, leaving a huge crater. And that's what happened at Yellowstone over 630,000 years ago. Okay, so I've heard this described as a supervolcano. This is, you know, you have volcanoes, and then I guess the way it works is you have bigger supervolcanoes. Is that is that is that essentially what we're talking about?
SPEAKER_07: Yeah. So supervolcano is kind of a funny term. Most geologists are going to roll their eyes when they hear the term supervolcano. And these days, it does have a scientific definition of volcano is considered super if it's had at least one explosion that released more than 240 cubic miles of material, which is a little bit more than twice the volume of Lake Erie.
SPEAKER_06: Okay, that sounds pretty super. I mean, you roll your eyes, but like to me, the common volcano lover is that's pretty, it's pretty intense. Well, no, so super the reason for the rolling the eyes, though, is that supervolcano isn't
SPEAKER_07: really a technical term. This term came back, I believe it was first used in like the early 1900s in a travel log, and it was really, I mean, it was a descriptive term, it wasn't a scientific definition.
SPEAKER_06: But now, supervolcano is used by some to refer to the biggest of volcanoes. Still, there is a more technical definition. Similar to the Richter scale that measures the strength of earthquakes. There's a scale called the volcano explosivity index, it measures the size of a volcanic eruption based on magnitude and intensity. A zero on the scale is non explosive, and eight is a super eruption.
SPEAKER_07: All a volcano has to do is have an eruption that big once and then we considered a supervolcano for here on out, even though perhaps all the other eruptions it's had are tiny, it doesn't matter. So it creates this sort of fear around these features and kind of mythos that is not necessarily true.
SPEAKER_06: Even if a volcano doesn't get to a level eight, it can still cause major problems. For example, in 1815, Mount Tambora, located on the island of Sumbawa in present day Indonesia, erupted as seven.
SPEAKER_07: And it created this superheated plume of hot ash and gas that went 28 miles into the sky. And then when that collapses, it produces what's known as pyroclastic flows, or which are essentially avalanches of searing hot rock and gas that rush down the sides of the volcano. At the same time in the 1800s when this happened, it killed around 10,000 people, they think. But then the gases and the ash that were in the atmosphere caused kind of darkened skies, it blotted out the sun. They sometimes call this the year without summer because it was so sort of dark and cold and so they had extensive crop failures and starvation disease. And there are some estimates that suggest that it killed around 82,000 more people in the year after, or years after that eruption.
SPEAKER_06: For context, Mount Tambora was the biggest eruption recorded in modern times, 40 times bigger than the 1980 eruption at Mount St. Helens. But if Yellowstone had a super eruption, it would be 10 times bigger than the eruption at Mount Tambora. So what's the likelihood of that? Well each of the three Yellowstone super eruptions has occurred about 600,000 to 800,000 years apart, with the last one taking place just over 630,000 years ago. So maybe we're overdue. Perhaps we do need a method to defend humanity from super eruptions like was suggested in the NASA paper.
SPEAKER_05: This is something that we hear an awful lot. Yellowstone is overdue for an eruption and I don't know where this comes from.
SPEAKER_06: That's Mike Poland, he's a geophysicist with the US Geological Survey and the scientist in charge of the Yellowstone Volcano Observatory. Is the guy in charge of looking for signs this might happen?
SPEAKER_05: There's no such thing as overdue in volcanoes. A volcano will erupt when it has a sufficient supply of eruptable magma, a lot of molten material, and pressure to get that magma to the surface. And right now, neither one of those conditions is in play at Yellowstone. There's no schedule or timetable. There may be average recurrence intervals, but that doesn't make anything due or overdue.
SPEAKER_06: Okay, so maybe Yellowstone isn't overdue, but it could still erupt at some point soon, right? Well, not necessarily. To understand why, you need to know a bit about what causes volcanic eruptions.
SPEAKER_05: You could think of magma almost like a soda. Sodas have carbon dioxide dissolved in them, right? That's a carbonation. Magma is the same way. It has a lot of gas dissolved in it, mostly water, carbon dioxide, some sulfur, sulfur gases. The thing when volcanoes erupt is gases are coming out of solution and driving the magma upward. So, it's a bit like shaking a soda and then opening it.
SPEAKER_06: In addition to these gases, the magma's viscosity, or its resistance to flow, basically its thickness, also affects its behavior.
SPEAKER_05: Gases get trapped in that more viscous stuff. And so, generally, the more viscous stuff is more explosive. But at Yellowstone, we see both behaviors. We see very explosive eruptions, like the one that created the big caldera 631,000 years ago, but also lava flows. The same composition of magma comes out of the ground, but it sort of lost its gas already. It's lost that big oomph that makes it blow up. And so, when it rises to the surface, it makes these very big, very thick lava flows. And in fact, when you're standing at a place like Old Faithful, looking all around you at these high plateaus, those are all lava flows around you that are over 100,000 years old for the most part.
SPEAKER_06: The source of all this heat is something Mike calls a hotspot, which melts the crustal plate under Yellowstone. But it's not like there's a boiling cavern of molten rock down there waiting to explode.
SPEAKER_05: Based on seismic imaging studies, that's sort of like taking an MRI of the Earth, we can see that only about 5 to 15% of the magma body beneath Yellowstone is molten. So it's mostly solid, but still hot, kind of plastic-y, mushy. It stretches underneath the entire caldera system, which is tens of miles across. And it is about 5, 10 miles thick in terms of its depth extent. Still a lot of molten rock. It's still an impressive amount. But it's sort of like concrete that's hardening. There's just not as much magma as would be needed to generate one of these massive explosions.
SPEAKER_06: Mike says the Yellowstone caldera might never erupt again because a hotspot could move over time. So a natural super eruption doesn't seem likely. But maybe humans, some rival power of the US, let's say, could force it to erupt. There are all kinds of internet rumors claiming that if a nuclear bomb were dropped on Yellowstone, that would trigger a super eruption.
SPEAKER_05: This is a pretty common question. And no, that would not work. This experiment has been run before, in a way.
SPEAKER_06: In 1959, a powerful earthquake shook the Yellowstone region.
SPEAKER_05: So essentially, it was like having a nuclear weapon go off underground, right next to the magma chamber. A magnitude 7.3 earthquake. That releases the energy equivalent to a good-sized nuclear weapon. And obviously, we're still here talking.
SPEAKER_06: OK, so we're not facing an imminent Yellowstone Armageddon. But what about the idea that this heat source could be harvested as energy?
SPEAKER_01: When man is what is now called civilized, he tries to fight against ignorance, tries to understand.
SPEAKER_06: That's Polish-born French volcanologist Haroon Tazieff in the 1973 National Geographic TV special, The Violent Earth.
SPEAKER_01: Doing things against what seems to be unvanquishable is also extremely exciting. Both of these very human tendencies are at the base of our try to understand volcanoes.
SPEAKER_06: So the Yellowstone supervolcano isn't an imminent threat to inhuman civilization. What about using its heat to generate massive amounts of relatively clean energy? Renewable energy, of course, is all the rage, right? Is there a way we could harness all that free heat under Yellowstone to reduce our carbon footprint? Seems like a no-brainer. Well, yeah, I guess I would read it somewhat differently.
SPEAKER_03: Partly because I don't think we need to go to Yellowstone. The Yellowstone basin is obviously bigger than the national park itself. But there's a lot of good reasons why we probably don't want to disturb our national parks. That's one thing. But on the other hand, do we really need to have that kind of resource to do the sort of things I'm talking about?
SPEAKER_06: That's Jeff Tester. He's a professor of sustainable energy systems at Cornell University. I called him up to better understand this aspect of the NASA paper about harnessing Yellowstone's geothermal potential.
SPEAKER_03: A lot of people have this solution that technology will all of a sudden perform a miracle and will just do this and we'll be done with it. But I don't think that a supervolcano is necessarily the sort of panacea of what we want right now. We want to take what we learn from a place like Yellowstone, what does it tell us about the behavior of the earth, and can we use it in other ways in a much more distributed fashion, more accessible to everybody in the country.
SPEAKER_06: Jeff has been studying and building geothermal energy systems for nearly five decades. He told me that for years people have been coming up with grand ideas for geothermal power generation, especially as new tools allowed them to drill deeper and deeper to tap into the boundless heat inside the planet.
SPEAKER_03: When I was a young engineer I had the privilege of going out to New Mexico to work with some pretty bright scientists at Los Alamos and they were designing at that time a drill that was melting rock. They were really thinking in kind of a similar way to the NASA sort of story, you know, we're going to just drill forever and just create a huge energy source. They never achieved that, but they did do some things that opened up the area of geothermal.
SPEAKER_06: Actually, humans were producing geothermal electricity long before that. In fact, they've been doing it for more than a century. It's a pretty simple process. Use the underground heat to make steam, which then drives power turbines that generate electricity. Italian engineers built the first geothermal power plant in Lardarello in 1904. Today, those plants still provide about 27% of the electricity for the region of Tuscany. But today, the U.S. is actually the largest producer of geothermal electricity, with 93 geothermal power plants spread across eight western states. Most are in California.
SPEAKER_03: The California site at the geysers field is one of the biggest geothermal resources in the world with respect to power production, and it's in a naturally high gradient area.
SPEAKER_06: The geysers field, about 100 miles west of Sacramento, houses the largest complex of geothermal power plants in the world. Together, they generate enough electricity to power a city the size of San Francisco. But generating electricity isn't the only way to use geothermal power. You can also use it for heat in the winter.
SPEAKER_03: If you can imagine, let's take a suburban community, okay, and instead of each house being, you know, having its fuel oil or its natural gas delivered, we would replace that system with pipes that would bring hot water to that house. So you've got a pipe going to your house and a pipe coming back that's bringing colder water. It gets heated up in the geothermal plant, the heating plant, and then it comes right back to you again. So it's a closed loop in a closed water system.
SPEAKER_06: This is called a district heating system, and the beautiful thing about it is you don't need very high temperatures, so you don't have to be near a supervolcano. You can tap into the Earth's natural furnace from practically anywhere. Iceland and some areas of Paris have district heating systems powered by geothermal heat. Jeff says that many parts of the U.S. could benefit greatly from wider use of geothermal heating systems, and these could have a major effect on climate change.
SPEAKER_03: We need to have a lot of heat for certain parts of the country. I don't know where you're from, but we live in a cold part of upper New York State and a good portion of the, what I'll call the northern tier of the United States, from the tip of Maine all the way through the Rockies and even into Montana and Oregon and Washington have very big regions where it's cold in the winter. Their carbon footprint, if you will, tends to be much more significantly controlled in some sense by heating.
SPEAKER_06: Previously, many of these places, especially those east of the Mississippi, wouldn't have been considered candidates for using geothermal, because the rock beneath them isn't that hot. But you don't need super hot rock.
SPEAKER_03: As long as we're close to the boiling point of water or slightly below, that would be 212 degrees Fahrenheit or somewhere around 180 or 150 even degrees Fahrenheit. That's going to be usable for heating homes, for sure, and buildings.
SPEAKER_06: In fact, Cornell University is planning to drill a 10,000 foot exploratory borehole. They hope to eventually heat the campus with geothermal energy.
SPEAKER_03: We're hoping that we'll get to temperatures at that depth, and I'm pretty confident we'll get to the temperatures of the range that we've been talking about. Close to the boiling point, 80 degrees centigrade or so, plenty hot enough.
SPEAKER_06: These advances are promising, especially as our species' appetite for more energy continues to grow exponentially. And right now, with the war in Ukraine and rising energy prices everywhere, many nations are concerned about energy self-sufficiency. One country that's long been focused on using geothermal to become energy self-sufficient is Iceland.
SPEAKER_03: Iceland's on a volcanic island. They don't have any fossil resources, so they had to import everything. Oil that they needed for transport, for heating, they imported a lot of coal. And that gave them a big incentive to sort of use the resources they had, which in Iceland's case are geothermal and hydro.
SPEAKER_06: 99.9% of Iceland's electricity comes from renewables. More than 25% of that is from geothermal, and most of the rest from hydropower. Meanwhile, 90% of its homes are heated with water from geothermal sources. They also used it in systems to melt the snow from sidewalks and parking lots.
SPEAKER_03: So they've managed over a period of roughly, I would say, a half a century, 50 years, to kind of transform their whole system over to geothermal heating. You know, on the time scale of climate change, that's kind of the time frames we should be talking about. We should do this in a couple of years. But if we get started, you know, that sort of transformation, I think, would be possible.
SPEAKER_06: And Iceland is exporting their knowledge.
SPEAKER_03: So the Icelandic government, some time ago, many years ago, decided that it wanted to help out developing countries by essentially sharing its technology by training people to bring them to Iceland and essentially give them a free education, if you will, with respect to geothermal technology.
SPEAKER_06: Researchers in Iceland and elsewhere are attempting to take geothermal to the next level by drilling into some of the planet's hottest areas.
SPEAKER_03: If we're going to make electricity, we've got to get to somewhat higher temperatures to make this thing make economic sense.
SPEAKER_06: One way to reach really high temperatures would be to tap directly into the magma. Scientists in Iceland have started testing this idea with the hope of one day harvesting super-efficient and abundant energy.
SPEAKER_03: The real challenge here is the subsurface science and the geology involved and whether you could make this really work.
SPEAKER_06: But as great as geothermal could be, it's not without its potential drawbacks. Injecting water into the ground can induce earthquakes. Most of these are too small for a human to feel, but people who live near the plants have reported the occasional small quake. It can also alter the nearby geology in ways that aren't fully understood. So if you built a plant close to Yellowstone, it could have a major unintended impact.
SPEAKER_07: By tapping into the geothermal power directly in the park, there's risk of losing the geysers and everything that Yellowstone is.
SPEAKER_06: In fact, this has happened before. In New Zealand, a geothermal plant was built in the Wairakei Basin in 1958, and the geysers there subsequently disappeared. Okay, so back to the NASA report. I reached out to Brian Wilcox, the lead author on the paper, which originally came out in 2015. Back then, Brian was an engineer at the agency's Jet Propulsion Laboratory, and I asked him how a NASA engineer had come to look at super volcanoes. I was on a panel looking at planetary defense, defense of Earth from asteroid impacts, you
SPEAKER_04: know, asteroid and comet impacts. Yeah, so NASA is keeping track of all the big stuff in space that could hit Earth and
SPEAKER_06: cause a similar type of result as a super volcanic eruption. After all, a massive asteroid strike is what scientists believe ended up killing the dinosaurs. Brian says that NASA has pretty well identified and is tracking all the major asteroids that could pose a threat.
SPEAKER_04: So really that problem is being largely addressed. And I had thought about super volcanoes as another threat because they do a very similar thing. They put dust in the high, high in the atmosphere.
SPEAKER_06: And remember, dust in the atmosphere darkening the sky is what threatens agriculture and the world's food supply. As Brian looked at the data, he noticed that statistically, Earth has experienced more super volcanic eruptions than major asteroid impacts. So it seemed that if you're worried about planetary defense, Yellowstone and Earth's other super volcanoes ought to be considered. So his team created their report as a way to examine this problem, to reframe the conversation about defending the planet. But at the same time, Brian's quick to point out that he's an engineer, not a volcanologist.
SPEAKER_04: But I wanted to basically apply engineering skills to the question, could humans prevent a super volcano from from causing this, you know, nuclear winter, asteroid winter, you know, volcano winter?
SPEAKER_06: Brian says that once the report got out into the media, it tapped into some old fears, specifically concerns about drilling inside Yellowstone National Park. He knows that the report never suggested that. And it breathed new life into some old myths that were circulating on the internet. And then it took on a life of its own. Yeah, I think I've heard that story before. But Brian also points out that people shouldn't revile volcanoes. And this is something that Maya spoke passionately about as well. Yes, they're powerful. And if you happen to be near one erupting, it can be dangerous. But we need volcanoes.
SPEAKER_07: Volcanoes are really beneficial to society as a whole. I mean, the reason why we have so many people near volcanoes is partly because volcanoes bring up these sorts of ash and rock that produce these are like nutrient rich things as they break down and release and create these really fertile soils. And they have these geothermal potential. And so people tend to settle around them.
SPEAKER_06: Even if you live far away from volcanoes, you still may benefit from them.
SPEAKER_07: You can get basalt rock, which is a type of rock that comes from volcanoes, that they grind up into a fine powder and you can put it in your plants. It's a common gardening additive to add nutrients and it also holds water.
SPEAKER_06: And if you're one of the billions of people who've taken a COVID test, well guess what? The enzymes used in the PCR tests, they come from studying heat resistant microbes living in the thermal ponds of, you guessed it, Yellowstone. So our message today, fellow earthlings, is fear not the Yellowstone supervolcano. You may visit the national park safe in the knowledge it will not blow up under you. And while you're there, think of all the benefits of volcanoes, including music. Some of the music in this episode was created by a geophysicist named Paulo de la Versana, who used seismic data and volcanic sounds to compose it. In fact, you're listening to it right now. If you like what you hear and you want to support more content like this, please rate and review us in your podcast app. And please consider a National Geographic subscription. That's the best way to support overheard. Go to natgeo.com slash explore more to subscribe. Articles written by Maya Wei Haas, including one about the creation of the PCR test, can be found at natgeo.com. And if you want to learn more about the Yellowstone Volcano Observatory, check out their website, usgs.gov slash observatories slash yvo. You can also check out a story about Brian Wilcox's new project, harvesting energy from ocean kelp farms. To hear more geo music, check out geophysicist, data scientist and musician Paulo de la Versana's YouTube channel. That's all on the show notes. They're right there in your podcast app. This week's overheard episode is produced by Kyrie Douglas. Our producers include Ilana Strauss. Our senior producers are Brian Gutierrez and Jacob Pinter. Our senior editor is Eli Chen. Our manager of audio is Karla Wills. Our executive producer of audio is Devar Artilon, who edited this episode. Our fact checkers are Robin Palmer and Julie Beard. Our photo editor is Julie Howell. Ted Woods sound designed this episode and Hans Dale Su composed our theme music. Thanks to the acoustic Atlas at Montana State University, the National Park Service and recorders Shan Berson, Peter Cumley, Neil Herbert, Jennifer Jarrett, Jeff Rice and John Trainor for providing the sounds of Yellowstone used in this episode. And thanks to the Apple podcast user who goes by the handle The Blob of Death for suggesting we do an episode on super volcanoes. This podcast is a production of National Geographic Partners. Whitney Johnson is the director of visuals and immersive experiences. Nathan Lump is National Geographic's editor in chief. Welcome aboard, Nathan. And I'm your host, Peter Gwen. Thanks for listening and see you all next time.
