Episode 13: Solving the mystery of the boiling river

When Andrés Ruzo was a boy growing up in Peru, he learned of an old Incan legend: a “boiling river” hidden deep in the Amazon. Today he sets out to find it.

National Geographic Explorer Andrés Ruzo takes a bridge over the “boiling river” in the Peruvian Amazon. Scientists didn’t know this unique waterway existed until Ruzo—whose aunt took him there in 2011—brought it to light.
Photo by Devlin Gandy

As a boy growing up in Peru, Andrés Ruzo recalls his grandfather’s stories about the horrors Spanish conquistadores encountered in the Amazon, including a “boiling river.” Years later, Ruzo, a National Geographic Explorer, journeys into the Amazon to try to find the waterway.

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ANDRÉS RUZO (SCIENTIST): My grandfather, my dad’s dad, he was just a really fantastic storyteller. There’s this one story that he would tell about Paitití. 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.

PETER GWIN (HOST): That’s National Geographic Explorer Andrés Ruzo.

RUZO: When the Spaniards come 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 conquistadores. This story takes place after that. So the Inca have now been conquered. Their sacred temple, 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 conquistadores kept showing up. You had the next wannabe Cortez, the next wannabe Pizzaro. And they were going in hungry for more gold and glory. These wannabe conquistadores 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 sidenote here is 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, you know, 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. And one of the details was a river that boiled, and that's really where the rest of this story, at least, takes off.

I’m Peter Gwin, 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 Andrés’s grandfather’s story ends. Because that tale would end up leading Andrés, like the Spanish conquistadores, 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.

Over the years, Andrés 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.

RUZO: The spiders that eat birds, the Goliath bird-eating spider. We know that now. And, you know, the anaconda as well.

GWIN: But the boiling river? That was clearly a myth, right? I mean, if anyone should know, it’d be Andrés.

You see, Andrés 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 Ph.D. in 2009 and worked with the Peruvian government, researching Peru’s geothermal systems.

RUZO: They started mapping out hot springs across the country, and they found a bunch in the Amazon. And 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? And their answer was no.

GWIN: But it was like a light bulb had been turned on. Andrés couldn’t stop wondering about it.

RUZO: And I ended up spending about two years asking the question of, honestly, anybody I could get my hands on from mining companies, oil and gas companies, geological surveys. And, I mean, the answer ended up being no. No one had ever recorded a large thermal river in the Amazon.

GWIN: 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 Andrés for even asking the question.

RUZO: 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. And I tell him about it. And he’s basically like, “Andrés, your geothermal stuff is cool. Stop asking stupid questions about …” He literally said that. He was, like, you know, “You’re …”

GWIN: Oh my gosh.

RUZO: 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.” So he definitely was like, “Please, for your own good, stop asking stupid questions.”

GWIN: Oh my gosh. Wow.

RUZO: I guess, like, I take a different approach with science. Curiosity is the heart of science.

GWIN: This is the part when Steven Spielberg in the, in the Steven Spielberg movie of your, of your, of your search, it’s like, you know, for your own good for your own, for the safety of your family for your sanity, for everybody, for your reputation, the good of your reputation, Andrés, stop asking these silly questions.

RUZO: So then I literally go home with my tail between my legs from that meeting, being like, oh my God, I’m an idiot.

GWIN: So Andrés 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’s his research going?

RUZO: And, and I’m sitting here thinking like, well, I should be like, oh, well geothermal energy in Peru, blah, blah, blah, blah, blah. But I’m like, Oh man, I'm like, well, this happened today. So I kind of spill the beans on feeling humiliated.

GWIN: And that’s when his aunt says something unexpected.

RUZO: So she kind of looks at me, goes, “Bbt no, Andrés, there exists a boiling river in Peru, and it’s huge. And I’ve been there. In fact, I even swum in the river.” And I’m looking at her like, OK, you had a little bit, one too many pisco sours, 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, Andrés, I’ve been there.”

GWIN: And then his uncle chimes in, Oh yeah, he’s been there too.

RUZO: And both of them kind of in unison start, “Well it’s so big that, I mean, it’s, 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 ’cause 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 …

GWIN: Wow.

RUZO: “What are you talking about”?

GWIN: Andrés’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. Andrés’s aunt tells him that there’s actually a community that lives at the river.

RUZO: So I’m kind of mind blown. My, you know, OCD kicks in. I can’t focus on anything else.

GWIN: For months he dives into researching this, trying to find some sign of the river.

RUZO: 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.

GWIN: 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.

RUZO: And the only lead that I found was one really old paper from 1965 that referenced another paper from the forties that said a “small, warm spring” in this area.

GWIN: A small, warm spring is not the kind of thing 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.”

RUZO: She was literally like, “We need to go to the jungle.”

GWIN: So, they book plane tickets. They’ll fly from Peru’s capital, Lima, to Pucallpa, a small city close to the jungle.

RUZO: I get really excited about things, if you can’t tell. I’m an excitable person, I guess, a good, stereotypical Latino there, right? And so I am so excited the night before, I can’t sleep at all.

GWIN: But alongside the excitement is dread. What if his aunt is wrong? Andrés had told his Ph.D. committee about his plan to find the river. This could all turn out to be humiliating.

RUZO: Some of the people on my Ph.D. committee as well were not terribly keen of this sort of, like, distraction.

GWIN: So they fly to Pucallpa and meet up with the shaman’s apprentice, who picks them up in a 4x4, and off they go, heading down a dirt road.

RUZO: So imagine being like a bumpy road, and then you get to the Pachitea River, this big beautiful, you know, muddy, chocolatey brown Amazonian river.

GWIN: They leave the 4x4 and get into a motorized canoe.

RUZO: In Peru, like, you know, we call them peke pekes. You turn on the motor, and it makes a peke, peke, peke, peke sound.

GWIN: So as they’re cruising down the river, the shaman’s apprentice turns to Andrés.

RUZO: He goes, “Andrés, stick your hand in the water.” And I stick my hand in the water, cold, you know, muddy, brown, chocolatey Pachitea River. Suddenly we start gliding into this plume, and it was sort of like an olivey-green color.

GWIN: Andrés can feel the water go from cold to lukewarm to hot.

RUZO: It’s not boiling, but it certainly is, you know, hot bathwater, very hot bathwater. And that, that did catch my attention, but I’m sitting here thinking like, Oh God, you know, the hot bathwater river of the Amazon. Great.

GWIN: (laughs) Doesn’t have the same ring, yeah.

RUZO: Yeah, exactly, not the same ring to it at all. So I talk to the … the shaman’s apprentice laughed. And he’s like, “Andrés don’t worry about it. We got to walk.”

GWIN: So they get out of the canoe and start walking up a muddy jungle trail. They 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.

RUZO: And everyone’s just quiet. And in the background I hear this like, shhh, shhh, shhh … it, it really reminded me like of a surge or of a really low surge or ocean waves, the sound of an ocean wave that was constantly crashing.

GWIN: Andrés turns to the shaman’s apprentice.

RUZO: 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 nod. And I look at him like, “What?”

GWIN: The apprentice points down at a valley.

RUZO: 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, this ridge, running as fast as I possibly can.

GWIN: And he gets to this lush patch of trees.

RUZO: 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’s 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?

GWIN: Even the air around him feels different.

RUZO: 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.

GWIN: But this is out in the open air. I mean, you’re, you’re having that sensation out in the open air, just adjacent to the river. Is that right?

RUZO: Absolutely. And what’s more, this river, there’s 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, it was, there was something alive to it. There was something magical about the place that was just, I mean, the word “enchanting” is the only thing that can come to mind.

GWIN: But Andrés 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 Andrés 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.

RUZO: Hot enough to kill you. Above 47 degrees C or 117 degrees Fahrenheit. That’s kind of the number where water starts to cook. I worked at Starbucks for two years ’cause undergraduate is expensive. And one thing I learned from Starbucks is that that 117 degrees number works.

GWIN: Andrés runs over to the river and puts a thermometer in the water.

RUZO: And 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.

GWIN: The legendary boiling river from his grandfather's story was real. It was incredible. And what was even weirder is 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, Andrés had a thought that made his heart sink.

RUZO: Oh, crud, what if I walked into an oil field cover-up? What if this was a small warm spring that turned into a large thermal river?

GWIN: 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.

RUZO: A really crazy mind-blowing one is the Lusi mud volcano in East Java. This is where an oil and gas well drilled into a geothermal system that they were not prepared for.

GWIN: We’re talking seven square miles flooded with boiling mud and water, displacing more than 40,000 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. Andrés 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, Andrés finds answers that make him completely reconsider what it means to be a scientist.

And … we share a moment from our new project, Soundbank.

We’ll eavesdrop as Andrés makes a new friend.

More after the break.

GWIN: That night, back at the riverside, Andrés is exhausted and he goes right to sleep. And he wakes up the next morning, still tired.

RUZO: I’m not a morning person. So I see the shaman’s apprentice, and I’m sitting there like, uh, I need coffee or tea or something. And he just, you know, he, he just gives me, uh, literally gives me a mug. He gives me a tea bag, and I’m sitting here like, yeah, tea bag and mug, man, uh, any water, you know? And he just laughs and he points, literally points down to the river. And I was like, what?

GWIN: (laughs) Hey, Mr. scientist guy, we’ve got some boiling water for you.

RUZO: Exactly.

GWIN: So he dunks the mug and makes his tea.

But there’s another problem. If Andrés wants to study the river—and get to the bottom of whether it occurs naturally or is somehow human induced—he has to convince the shaman to give him permission. And that could be tricky. Ever since the Spanish, locals have become wary of outsiders always coming to the Amazon looking for treasure—miners, loggers, poachers, it’s a long list ... And to make things even harder, Andrés is a scientist doing geothermal exploration.

RUZO: Guess who has a lot of those? Oil and gas companies, mining companies, people who tend to be very exploitive.

GWIN: Andrés needs the shaman, Maestro Juan Flores, to trust his intentions really are good. So he goes to talk to him.

RUZO: He’s not very tall. You know, very tan skin, his hair is kept pretty short. He’s got very perceptive eyes.

GWIN: And right off the bat, Maestro Juan Flores asks Andrés, “Why did you come here?” And Andrés starts telling his story.

RUZO: 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.

GWIN: So Andrés finishes his story and just waits, hoping Maestro Juan Flores believes him.

RUZO: 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.

GWIN: Maestro Juan Flores tells him he’s free to study the river, which, by the way, has a local Quechua name:

RUZO: Shanay-Timpishka. It literally means “boiled with the heat of the sun.”

GWIN: 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?

RUZO: I have no idea. I just talked and, and it’s, 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. He’s like, ultimately it didn’t really matter what you said. I could read in you that I could trust you.

GWIN: So Andrés 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.

RUZO: They accidentally dropped a DSLR in the boiling river.

GWIN: Whoops.

RUZO: They’ve got it on film. It melted, man. I felt so bad for them.

GWIN: Humans don’t do well in boiling water either.

RUZO: This is a dangerous place to work. I guess the most useful thing out of schooling was going back to like kindergarten and first grade. Ever play The Floor is Lava! game? That is the best thing you can study up on for working a geothermal system sometimes.

GWIN: Andrés 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.

RUZO: I believe it was 2014. There was a local person who ended up falling in and dying.

GWIN: Oh my God.

GWIN: At one point, Andrés 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.

RUZO: 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 and a boiling river. And it was one of the more unpleasant experiences in my life because you just had to take the wasp stings.

GWIN: Ahh geez man.

GWIN: Another time, one of his team members is walking through a thermal marsh—think muddy bog infused with boiling water.

RUZO: Which is unbelievably dangerous ’cause you have to go with a stick and start stabbing before you step.

GWIN: The guy accidentally steps in a soft spot and sinks into the hot mud up to his shins.

RUZO: His skin bubbled up like a plastic bag full of water. It’s disgusting.

GWIN: Holy cow..

RUZO: Second- and third-degree burns in a matter of seconds.

GWIN: And then the poor guy has to WALK through the jungle to get to a hospital.

RUZO: Oh, and we got extra unlucky ’cause fire ants started moving through the path that we were on, with these swelled-up legs. I mean, it was awful.

GWIN: After a whole lot of pain, the guy finally makes it to a hospital.

RUZO: Marshall, if you’re hearing this, you know, stick that chest out, man, because he was saying that like he won in the entire, like, burn ward as far as the coolest burn story.

GWIN: But one of the hardest parts of researching the boiling river has nothing to do with boiling water.

RUZO: 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.

GWIN: 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 decade since he’s been going there, Andrés has seen evidence of that devastating trend firsthand.

RUZO: When you see trees that were as big around as your car is long just disappear, one year to the next, that hits you.

GWIN: And those ancient trees, the true gold of the Amazon, they aren’t coming back. And yet, a lot of people don’t want Andrés doing the work he does. They don’t want anyone shining a light on what they’re doing. Illegal loggers had 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.

RUZO: It was a place of legends and spirits. This was a place where you would go to commune with nature.

GWIN: 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.

RUZO: He made the conscious effort: No, I’m going to claim the sacred space to protect it.

GWIN: And so he was the one who established a community there, made up of a mix of different Indigenous groups.

RUZO: The people who are now at the boiling river are mainly Asháninka, but there is a lot of Shipibo influence as well. And there’s a lot of mestizo. Right now, most of us in Peru are mestizo, where we can claim, you know, both European descent as well as Indigenous descent.

GWIN: So after years of obsessing over his grandfather’s story, Andrés found the legendary boiling river. But the big mystery—why few people in the outside world seemed to know about it—remained until Andrés found an important clue: an old geological report buried deep in university archives.

RUZO: There is a wild oil and gas history that leads to why the site was never documented.

GWIN: 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.

RUZO: They were freaked out because volcanoes and oil and gas reservoirs generally do not go hand in hand ’cause you'll overcook your reservoir, and it’ll be worthless. This is 1929 stock market crash. You do not want to freak out investors.

GWIN: So they played down the river to protect their investment, and it stayed undocumented. It actually was an oil industry coverup, just not the one Andrés had expected. Companies covered up the discovery of the river—–but they didn’t create it. After all the research, getting chased by wasps and stepping in thermal marshes, Andrés finally figures it out: The river itself IS natural. And the heat comes from deep inside the Earth.

RUZO: 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 “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 “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 you.

GWIN: Andrés has 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’s 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.

RUZO: The Milky Way—they, one of the shamans was telling me, is the great celestial river. You have the boiling river here on Earth, which is said to be home to the Yacumama, 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 rivers.

GWIN: And all of that made him reconsider what’s meant by the word “sacred.”

RUZO: The sacred to them is not, you can joke about it. You can, 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.

GWIN: This also prompted Andrés to reexamine some of his thinking about science. A lot of people don’t trust science. And that’s leading to huge problems.

RUZO: 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.

GWIN: And Andrés thinks he knows partly why this is happening.

RUZO: 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.

GWIN: 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 Andrés 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. And listening to the shaman and the local people had led him to a much broader understanding of the river and the rainforest surrounding it.

Andrés also recognized something the shaman had understood years before: Science was part of the story, but it wasn’t enough. You need personal connection.

RUZO: I get asked all the time, like, what is the best thing that I can do for the Amazon?

GWIN: And according to Andrés, the answer is deceptively simple: Go there.

RUZO: You have seen from the colonization times in Peru until the present, there has been a devalorization, 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 human interactions, underline human interactions, change hearts, change minds, and change perspectives. If I had my Make-A-Wish Foundation wish that I let everyone go to the Amazon, and in the most responsible way possible of course, but come visit the boiling river, please.


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 Soundbank—–Earth, one sound at a time.

Soundbank brings you the world through the ears of Nat Geo Explorers and journalists on assignment.

And Andrés 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.

All right, here’s the answer. This is Miley. She’s a monkey, a type called a saki.

She looks kinda like a grumpy baby who just woke up with crazy bedhead.

Miley was orphaned and kept as a pet in Peru, and on one of his visits to the boiling river, Andrés Ruzo met Miley.

As he puts it, Miley decided Andrés 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 Soundbank 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 Soundbank in more episodes of Overheard.

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/explore to subscribe.

And if you want to learn more about Andrés’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 details about Andrés’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 Ilana Strauss.

Our producers are Khari Douglas and Marcy Thompson.

Our senior producers are Brian Gutierrez and Jacob Pinter.

Eli Chen is our senior editor.

Carla Wills is our manager of audio.

Our executive producer of audio is Davar Ardalan.

Our fact-checkers are Robin Palmer and Julie Beer.

Hansdale Hsu 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, committed to illuminating and protecting the wonder of our world, funds the work of National Geographic Explorer Andrés Ruzo.

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 Gwin. Thanks for listening, and see y’all next time.


Want more?

Read Andrés’s book: The Boiling River: Adventure and Discovery in the Amazon.

Also explore:

Curious what you can do to help the river’s ecosystem? Go to www.boilingriver.org.

For subscribers:

Read a Q&A with Andrés to learn more about the communities that live around Shanay-Timpishka and the theories scientists explored to understand why the river boils.