Solving the Mystery of the Boiling River | Podcast | Overheard at National Geographic

My grandfather, my dad's dad, he was just a really fantastic storyteller. There's just one story that he would tell about Paititi. Paititi is in Peru, what we call El Dorado, right? The golden city. So imagine this big mysterious city made entirely of gold, hidden deep in the Amazon. That's National Geographic explorer Andres Russo.

When the Spaniards came into Peru, first they encounter the Inca. There's the 40 years of fighting between the Spanish and the Inca until the Incan empire is finally conquered by the Spanish conquistadors. The story takes place after that, so the Inca have now been conquered. Their sacred temples, sacred sites have been desecrated. Their gold, which was a symbol of life itself, has been melted and shipped off to Spain and the Iberian Peninsula.

But new waves of Spanish conquistadors kept showing up. You had the next wannabe Cortés, the next wannabe Pizarro, and they were going in hungry for gold and glory. These wannabe conquistadors go to the now humbled, conquered Inca and ask them, “Hey, where's another civilization we could conquer? We want more gold out of vengeance.” The Inca tell them, “Oh, you want gold? You know, go to the Amazon; you will find all the gold you want there. In fact, there's an entire city called Paititi.”

The side note here is that the Inca had tried to conquer the Amazonians multiple times and failed miserably. The Spanish are happy as can be, right? They go off in search of Paititi, looking for a lost city of gold. The few that return come back with these horrible stories of, you know, spiders as big as your hands that eat birds, giant anacondas that could swallow a man whole, poison arrows that could kill you in a nick, powerful shamans with spells that would drive men mad. One of the details was a river that boiled, and that's really where the rest of this story at least takes off.

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I'm Peter Quinn, editor-at-large at National Geographic magazine, and this is "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 dive into Amazonian legends. Our story starts where Andres's grandfather's story ends, because that tale would end up leading Andres, like the Spanish conquistadors, deep into the jungle, searching for a legend. And like the Spanish, he'd find much more than he bargained for. More after the break.

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Over the years, Andres has spent a lot of time thinking about the legend his grandfather told him, and bit by bit, he learned some of the pieces of the story were true. The spiders that eat birds, the Goliath bird-eating spider, we know that now. You know, the anaconda as well. But the boiling river? That was clearly a myth, right? I mean, if anyone should know, it'd be Andres.

You see, Andres grew up with family in Peru, Nicaragua, and Texas, and he often spent his childhood summers on a coffee farm in Nicaragua, where he'd play in the jungle by the side of a volcano. In some places, the heat inside the earth made it impossible for trees to grow on the surface. When he got older, he studied geology, in part because he was fascinated by the volcano on the coffee farm. He started his PhD in 2009 and worked with the Peruvian government researching Peru's geothermal systems. They started mapping out hot springs across the country, and they found a bunch in the Amazon.

When I saw that map, I was like, “Oh my goodness, that's so cool! Any, you know, big bad boiling rivers, if you will.” Their answer was no, but it was like a light bulb had been turned on. Andres couldn't stop wondering about it, and he ended up spending about two years asking the question of, honestly, anybody he could get his hands on—from mining companies, oil and gas companies, geological surveys. I mean, the answer ended up being no. No one had ever recorded a large thermal river in the Amazon. In fact, they told him it was impossible. You'd need a volcano nearby to make a boiling river, and there were no volcanoes nearby.

Finally, someone got annoyed at Andres for even asking the question.

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The last time I asked professionally, I was at a meeting with a mining company, and there was this really old, really well-established, you know, eminence of a geologist guy. I tell him about it, and he’s basically like, “Andres, your geothermal stuff is cool. Stop asking stupid questions about…” He literally said that! He was like, “You know, you… why are you gonna…” He was like, “This is… and he said it very kindly. You know, he was like, this is a piece of professional advice. You're coming off as like really great, really, you know, lots of novel stuff you're doing here with the geothermal work, but then asking about legends? That doesn't fit a professional, you know… that…”

So he definitely was like, “Please, for your own good, stop asking someone dumb questions.” Gosh, wow. That’s… I guess like I take a different approach with science. Curiosity is the heart of science! This is the part when Steven Spielberg— in the Steven Spielberg movie of your search—it's like, “You know, for your own good, for the safety of your family, for your sanity, for everybody, for your reputation, the good of your reputation, just stop asking these silly questions.”

So then, I literally go home with my tail between my legs from that meeting, being like, “Oh my God, I’m an idiot.” So, Andres decides once and for all to give up on the boiling river question, but that night he goes to his aunt’s house for a family dinner, and she asks how his research is going. And I’m sitting here thinking like, “Well, I should be like, ‘Oh, well, geothermal energy in Peru, blah, blah, blah…’” But I’m like, “Oh man, like well, this happened today,” and I, you know, so I kind of spill the beans on feeling humiliated.

And that’s when his aunt says something unexpected. So she kind of looks at me and goes, “But no, Andres, there exists a boiling river in Peru, and it’s huge, and I’ve been there. In fact, I even swam in the river!” And I’m looking at her like, “Okay, you had a little bit one too many pisco showers, I think, or you’re just messing with me and kicking me while I’m down.” And then she starts laughing, obviously! She’s like, “No, seriously, Andres, I’ve been there!” And then his uncle chimes in, “Oh yeah, he’s been there too.”

And both of them kind of in unison start, “Well, it’s so big that, I mean, it’s at least as wide as a two-lane road! It’s so hot you can’t touch the water! In fact, you can’t even put your hand over the water because the steam is so hot it’ll burn you. I mean, it’s flowing for at least 200 yards and a powerful shaman protects it.” And I’m sitting there like, “Wow, what are you talking about?” Andres’s aunt had advocated for the rights of Peru’s indigenous people, and she’d made friends with the wife of a shaman who told her about the river.

Andres’s aunt told him that there’s actually a community that lives at the river. So I’m kind of mind-blown; my OCD kicks in! I can’t focus on anything else. For months, he dives into researching this, trying to find some sign of the river. I start pulling up Google Earth. I am doing every sort of Google search you can possibly think of, and there was nothing! I could not find anything online. He reads through dozens of scholarly journals. The area his aunt is talking about is right near an oil mining facility. If there’s a boiling river nearby, the petroleum engineers would certainly have documented it.

And the only lead that I found was one really old paper from 1965 that referenced another paper from the 40s that said a “quote-unquote small warm spring” in this area. A small warm spring is not the kind of thing that the Incas would use to terrorize the Spanish, and it’s not the river his aunt described. So finally, his aunt tells him, “Hey, there’s only one thing to do.” She was literally like, “We need to go to the jungle.” So they book plane tickets; they'll fly from Peru’s capital, Lima, to Pucallpa, a small city close to the jungle.

I get really excited about things that you can't tell! I'm an excitable person, I guess. Good, good stereotypical Latino there! And so, I am so excited the night before; I can't sleep at all! But alongside the excitement is dread: What if his aunt is wrong? Andres had told his PhD committee about his plan to find the river. This could all turn out to be humiliating! Some of the people on my PhD committee as well were not terribly keen on this sort of like distraction.

So they fly to Pucallpa and meet up with the shaman's apprentice, who picks them up in a four by four, and off they go, heading down a dirt road. So imagine being on a bumpy road, and then you get to the Pachita River, this big, beautiful, you know, muddy chocolatey brown Amazonian river. And they leave the 4x4 and get into a motorized canoe. In Peru, like, you know, we call them “picket.” You turn on the motor and it makes a pick, a bigger, bigger sound.

So, as they’re cruising down the river, the shaman’s apprentice turns to Andres. He goes, “And today, stick your hand in the water.” And I stick my hand in the water—cold, you know, muddy brown chocolatey Pachitaya River. Suddenly, we start gliding into this plume, and it was sort of like an olive green color. Hundreds can feel the water go from cold to lukewarm. It’s hot! It’s not boiling, but it certainly is, you know, hot bath water, very hot bath water. Okay? And that did catch my attention, but I'm sitting here thinking like, “Oh God! You know, the hot bathwater river of the Amazon? Great!”

Um, didn’t have the same ring! Yeah, yeah, exactly—not the same ring to it at all. So I talked to the shaman’s apprentice, laughs, and he’s like, “Andres, don’t worry about it, we gotta walk.” So they get out of the canoe and start walking up a muddy jungle trail. The hike for an hour to the top of the ridge, and it’s the Amazon! So it’s humid, they’re tired, sweaty, and they take a breather, leaning against some giant trees, and everyone’s just quiet.

And in the background, I hear this… like it really reminded me of a surge, or of a really low… yeah, a low surge, or ocean waves—the sound of an ocean wave that was constantly crashing. Andres turns to the shaman’s apprentice because I’m like, “What is that?” He just laughs; he’s like, “That’s the river!” It was sort of like an “I told you so” moment, and I look at him. The apprentice points down at a valley, and in the middle of all these beautiful, deep dark green canopy trees, right? There’s this cloud of vapor.

So I bolt down this ridge, running as fast as I possibly can, and I get to this lush patch of trees. Imagine first the walls of green. You see these trees shooting up out of the jungle up to 60 feet or more, beautiful walls of green. You start going towards the center of the valley. There are these ivory-colored stones on either side of this absolutely beautiful, just transparent turquoise water. It looks so clean and inviting; you just want to like jump into it. But there is this veil of white smoke, white vapor just hovering over it, and I’m sitting here thinking, “What the hell am I walking into?”

Even the air around him feels different! When you're in a sauna, you can really almost feel that air in your lungs, almost, you know, and you can feel it burning. And that’s what it felt like. Almost like, “Oh my gosh! I feel my lungs!” sort of thing, but this is out in the open air? I mean, you're having that sensation out in the open air. Just adjacent to the river, is that right? Absolutely!

And what's more, this river, there are some rapids nearby, and that’s what was causing the thundering surge sound, and you could feel those vibrations. I mean, I was sitting on the stones, and you could feel the heat—not just from the sun radiating down, but from the earth itself! I mean, there was something alive to it! There was something magical about the place that was just… I mean, “enchanting” is the only thing that can come to mind.

But Andres isn't here to enjoy the scenery; he's here to answer a question: Are the legends true? Is there really a boiling river in the Amazon? And when Andres says he's looking for boiling water, he's not talking about water that’s just hot! And he’s not necessarily talking about the chemical boiling point either. He means something else, hot enough to kill you—above 47 degrees Celsius, or 117 degrees Fahrenheit. That’s kind of the number where water starts to cook. I worked at Starbucks for two years because undergraduate is expensive.

And one thing I learned from Starbucks is that that 117 degrees number works. Andres runs over to the river and puts a thermometer in the water. I take my first temperature measurement: it’s 187 degrees! I'm dumbstruck. I’m blown away! I'm sitting there like, “What is this?” The water is definitely too hot to touch! The steam on top of it is definitely too hot to touch! This thing is as wide as a two-lane road, even wider in what I'm looking at, and this is going for about 200 yards in a big curve! Just like my aunt and uncle had said, the legendary boiling river from his grandfather's story was real. It was incredible!

And what was even weirder was that no one had documented it—at least scientifically! This part of the jungle was right near an oil field. How had the petroleum scientists missed it? Suddenly, Andres had a thought that made his heart sink: “Oh crud, what if I walked into an oilfield cover-up? What if this was a small warm spring that turned into a large thermal river?” This kind of thing has happened before. Drilling projects go awry, and heat from deep in the earth shoots up, causing really extreme changes on the surface.

The really crazy, mind-blowing one is the Lucy Mud Volcano in East Java. This is where an oil and gas well drilled into a geothermal system that they were not prepared for. I mean, we're talking seven square miles flooded with boiling mud and water, displacing more than forty thousand people, and that eruption is still going on! So what if this boiling river was similar? Maybe an oil and gas well had gone wrong, turning what used to be a small warm spring into a giant boiling river. Andres had to figure it out.

Why did the river boil? Was it natural or man-made? Did someone try to cover this up, and if so, why? Coming up, Andres finds answers that make him completely reconsider what it means to be a scientist, and we share a moment from our new project, Sound Bank. Well, “Eavesdrop” is Andres makes a new friend. More after the break.

That night, back at the riverside, Andres is exhausted, and he goes right to sleep. He wakes up the next morning still tired. “I’m not a morning person,” so I see the shaman's apprentice, and I’m saying like, “Uh, I need coffee or tea or something,” and he just, you know, he just gives me a—literally, he gives me a mug. He gives me a teabag, and I'm sitting here like, “Yeah, teabag and mug, man! Any water?” You know? And he just laughs, and he literally points down to the river, and I was like, “Why?”

“Mr. Scientist guy, we’ve got some boiling water for you!” Exactly! Exactly! So he dunks the mug and makes his tea. But there’s another problem. If Andres wants to study the river and get to the bottom of whether it occurs naturally or somehow human-induced, he has to convince the shaman, Maestro Juan Flores, to trust his intentions are really good.

So he goes to talk to him. He’s not very tall, you know, very tan skin; his hair is kept pretty short, he’s got very perceptive eyes, and right off the bat, Maestro Juan Flores asks Andres, “Why did you come here?” And Andres starts telling his story. “I felt honestly so uneasy because he was just so stoic, but his eyes were not moving. But I could tell— it really reminded me of a snake. He’s not moving; he’s giving me very few cues on what’s going on in his head, but I know he’s digesting everything.”

So Andres finishes the story and just waits, hoping Maestro Juan Flores believes him. There’s this kind of like brief but awkward silence for me and then I just see this massive bright, white toothy grin, and he lets out this amazing laugh! It’s a laugh that you can just feel in your soul that makes you smile. Maestro Juan Flores tells him he’s free to study the river, which by the way has a local Quechua name, Shania Tim. It literally means “boiled with the heat of the sun.”

“How did you convince him that you weren't an oil guy and that he, you know, he should trust you to come and study the boiling river?” “I have no idea! I just talked, and I was nervous, and you know, later on he explained it to me. He’s like, ‘Look, when you’re with someone, you can read their heart. Ultimately, it didn’t really matter what you said. I could read in you that I could trust you.’”

So Andres goes back home, gathers a scientific team, and returns to start trying to solve the mystery of why the river is boiling. But there are some challenges! For example, cameras don’t do well in boiling water! They accidentally dropped a DSLR in the boiling river. Whoops! They’ve got it on film—it melted! Man, I felt so bad for them! Humans don’t do well in boiling water either. This is a dangerous place to work!

I guess the most useful thing out of schooling was going back to, like, kindergarten in first grade—ever play the “floor is lava” game? [Laughter] That is the best thing you can study up on for working at geothermal systems! Sometimes Andres may be upbeat, but he’s not kidding around; he’s describing an incredibly dangerous place.

Remember how his aunt had said she’d swum in the river? She could only do that because there’d been a heavy rainstorm one day and she jumped in while it was cool enough to touch! Otherwise, it would have been deadly! I believe it’s 2014; there was a local person who ended up falling in and dying. Oh my God! At one point, Andres and his team are clearing a path along a thin rocky ledge next to the boiling river. There’s a big rotten log blocking the way, and one of the guys hits it with a machete. And this swarm of wasps comes out, and we are chased by wasps trying to balance on this little rock ledge next to a thermal marsh in a boiling river!

And it was one of the more unpleasant experiences of my life because you just had to take the wasps! Oh, another time, one of his team members is walking through a thermal marsh—think muddy bog infused with boiling water—which is unbelievably dangerous because you have to go with a stick and start stabbing before you step. The guy accidentally steps in a soft spot and sinks into the hot mud up to his shins. His skin bubbled up like a plastic bag full of water. It’s disgusting! Second and third degree burns in a matter of seconds!

And then, the poor guy has to walk through the jungle to get to a hospital. Oh, and we got extra unlucky because fire ants started moving through the path that we were on! With these swelled-up legs, I mean, it was awful! After a whole lot of pain, the guy finally makes it to a hospital. Marshall, if you’re hearing this, you know, stick that chest out, man, because he was saying that like he won as in the entire burn ward as far as the coolest burn story!

But one of the hardest parts of researching the boiling river has nothing to do with boiling water. Mafias are hard at work here, and I myself have been threatened by a corrupt politician. And I think that’s one of the great difficulties of telling this story because it expands so quickly, and it gets us into hot water, you know, quite literally! The river is part of the forest; it’s intertwined with the ecosystem around it, and that forest is under threat as people keep chopping down trees! During 2020, people chopped down half a soccer field of the Peruvian rainforest every minute.

And over the decades since he’s been going there, Andres has seen evidence of that devastating trend firsthand. When you see trees that were as big around as your car is long just disappear from one year to the next, that hits you! And those ancient trees, the true gold of the Amazon, they aren’t coming back! And yet, a lot of people don’t want Andres doing the work he does. They don’t want anyone shining a light on what they’re doing! Illegal loggers have even threatened his team at gunpoint!

In fact, the community that lived by the river was actually established there to respond to these kinds of threats. Decades ago, there were no communities by the river. It was a place of legends and spirits. This was a place where you would go to commune with nature. But as modernization rolled in, the jungle started getting cleared. Loggers and farmers would cut down huge swaths. The shaman, Maestro Juan Flores, saw that the river was in danger. He made the conscious effort, “No, I’m gonna claim this sacred space to protect it.”

And so he was the one who established a community there made up of a mix of different indigenous groups. The people who are now at the boiling river are mainly Ashaninka, but there is a lot of Shipibo influence as well. There’s a lot of mestizo. Right now, most of us in Peru are mestizo; we can claim, you know, both European descent as well as indigenous descent.

So after years of obsessing over his grandfather’s story, Andres found the legendary boiling river. But the big mystery, why few people in the outside world seem to know about it, remained until Andres found an important clue. An old geological report buried deep in university archives! There is a wild oil and gas history that leads to why the site was never documented. Back in the 1920s, oil companies sent people to the Amazon to search for the 20th century’s version of gold, oil. But when they found the boiling river, they were horrified!

They were freaked out because volcanoes and oil and gas, you know, reservoirs generally do not go hand in hand because you’ll overcook your reservoir; it’ll be worthless! This is the 1929 stock market crash! You do not want to freak out investors! So they played down the river to protect their investment, and it stayed undocumented! It actually was an oil industry cover-up—just not the one Andres had expected! Companies covered up the discovery of the river, but they didn’t create it!

After all the research, getting chased by wasps, stepping in thermal marshes, Andres finally figures it out! The river itself is natural, and the heat comes from deep inside the earth! If you look down at your arm and imagine your veins and your arteries, and imagine hot blood running through those veins and arteries, the earth has its own “quote-unquote” veins and arteries! Those are the faults, the cracks! Right?

This is where water flows through the deep parts of the earth and has its own “quote-unquote” blood, i.e. geothermal waters! In this case, the deeper you go into the earth, the hotter it gets! In fact, at the core mantle boundary, you're looking at temperatures roughly as hot as the surface of the sun! Think of the boiling river as an earth artery where you have that hot water running up an earth artery—a fault—and heating up what starts off as a small, just ambient temperature cold stream right in the middle of the jungle.

And as it runs over all these big fault zones, it supercharges it to turn it into ultimately almost four miles of thermal flow, much of that hot enough to kill! Andres spent more than a decade visiting and studying the boiling river, and over that time, it’s become so much more than just a puzzle to be solved. He spent a lot of time just sitting on the rocks along its edge, looking up at the sky and thinking about how the local people see the river—the Milky Way.

One of the shamans was telling me, right? It’s the great celestial river. You have the boiling river here on earth, which is said to be home to the Yakuma, a giant serpent spirit who gives birth to hot and cold water. This is a place that connects both through the vapors of the river that take the prayers of nature, the intentions of nature, the wishes of nature and creation, up to the heavens.

So you’ve got this bridge between the spirit world, i.e. the Milky Way, the great celestial river, and on earth here, the boiling river. All of that made him reconsider what’s meant by the word “sacred.” The sacred to them is not—you can joke about it—you can be personal about it! You are dealing with a sacred space as if it was an old friend, if you will, rather than, you know, a holy of holies to be revered.

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This also prompted Andres to re-examine some of his thinking about science. A lot of people don’t trust science, and that’s leading to huge problems. We still have people arguing about the earth being flat, masks working, vaccines being real or not, evolution happening at all, you know, climate change happening at all. And Andres thinks he knows partly why this is happening.

“I think that points to a problem a hundred years in the making, maybe more, of science being held—knowledge being held hostage in the ivory tower! Ultimately, your science is nothing if it ends up sitting away, unread, unused, and rotting away in some archive! It needs to be… it needs to be out! We need to get science out of this hostage situation! We need to make science personal, just like the sacred! Science doesn’t have to be lofty and inscrutable, but something a person can explore, touch, experience!”

By the same token, scientists could learn a lot by listening to people in places like the Amazon. After all, if Andres had only read research papers and listened to his fellow scientists, he’d have given up on the legend of the boiling river a long time ago. Only by veering off the beaten path was he able to find something that had been hidden. Listening to the shaman and the local people had led him to a much broader understanding of the river and the rainforests surrounding it.

Andres also recognized something the shaman had understood years before: Science was part of the story, but it wasn’t enough; you need personal connection. “I get asked all the time, like, what is the best thing that I can do for the Amazon? And according to Andres, the answer is deceptively simple: Go there!”

You have seen from the colonization times in Peru until the present, there has been a devaluation, underappreciation of their culture, of their ways of life, of them as people. When some of my colleagues see people coming from, you know, New York or Shanghai or, or Madrid or Paris, anywhere, you know, someone who comes across the globe to see, “Oh, well those big trees have always been there!” Who cares? No! These people are coming and paying good money to see those big trees! Wait a minute! What they’re actually asking me? Questions about my culture!

Those inner human interactions, underlying human interactions, change hearts, change minds, and change perspectives! If I had my Make A Wish Foundation wish, I’d let everyone go to the Amazon, and in the most responsible way possible, of course! But come visit the boiling river!

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This year, we’re pushing our audio explorations even further to the edges of our big, weird, beautiful world. It’s a new segment called Sound Bank, Earth—one sound at a time. Sound Bank brings you the world through the ears of Nat Geo explorers and journalists on assignment. And Andres found out that sometimes when you’re exploring, you make a new friend.

I’ll tell you what this is in a second, but for now, just listen and imagine what might be making this sound. Okay, all right, here’s the answer: this is Miley! She’s a monkey—a type called a Saki! She looks kind of like a grumpy baby who just woke up with crazy bed head! Miley was orphaned and kept as a pet in Peru, and on one of his visits to the boiling river, Andres Russo met Miley! And as he puts it, Miley decided Andres was her new mom!

She would grab his arm and refuse to let go! He says this sound means there's a bird close by, and “I’m scared.” Have another listen! We’ll have more from our sound bank throughout the year. Get ready to immerse yourself in the world of a National Geographic explorer, 30 seconds at a time, with a distinct sound that reveals our audible earth! So listen up for sound bank and more episodes of Overheard.

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Hey, 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 forward slash explore to subscribe! And if you want to learn more about Andres’s work with the Boiling River, hey, the guy’s written a whole book on the subject! Check it out! It’s called The Boiling River: Adventure and Discovery in the Amazon. And check out www.boilingriver.org. There you can see photos of the river, discover its history, and learn how you can help protect it!

Also, you can read an article that goes into more detail about Andres’s research and many of the river’s unique qualities! That’s all in the show notes right there in your podcast app. This week’s episode of Overheard is produced by Elana Strauss. Our producers are Kyrie Douglas and Marcy Thompson. Our senior producers are Brian Gutierrez and Jacob Pinter. Eli Chen is our senior editor. Carlo Wills is our manager of audio. Our executive producer of audio is Devar Ardulon. Our fact checkers are Robin Palmer and Julie Beer. Hansdale Sue composed our theme music and also sound designed and engineered this episode.

This podcast is a production of National Geographic Partners. The National Geographic Society is committed to eliminating and protecting the wonder of our world. Funds the work of National Geographic explorer Andres Russo. Whitney Johnson is the director of visuals and immersive experiences. David Brindley is National Geographic's interim editor-in-chief, and I'm your host, Peter Gwynne. Thanks for listening and see you all next time.

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