Krakatau: The loudest sound in recorded history

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May 27th, 1883: Clouds pouring from the volcano on Krakatau in southwestern Indonesia during the early stages of the eruption which eventually destroyed most of the island. Royal Society Report on Krakatoa Eruption published in 1888 Lithograph credit: Parker Coward. (Photo by: Pictures From History/Universal Images Group via Getty Images)
May 27th, 1883: Clouds pouring from the volcano on Krakatau in southwestern Indonesia during the early stages of the eruption which eventually destroyed most of the island. Royal Society Report on Krakatoa Eruption published in 1888 Lithograph credit: Parker Coward. (Photo by: Pictures From History/Universal Images Group via Getty Images)

On August 27, 1883, a sound emerged from the Earth louder than anything recorded before — or since.

The volcanic eruption bellowed out from Krakatau, an uninhabited island between Java and Sumatra in Indonesia. Another island 3,000 miles away, near Mauritius, later reported an inexplicable, “distant roar of heavy guns.” That is like New Yorkers hearing an eruption at Mount St. Helens.

Below human hearing, infrasonic pressure waves rippled through the atmosphere and rounded the globe four times. Tsunamis slammed into nearby islands and reached the edge of South Africa, causing most of the event’s 36,000 fatalities.

The eruption at Krakatau, also known as Krakatoa, was one of the first natural disasters the world was talking about instantaneously, thanks to the telegraph. Studies of the event changed the course of scientific history and helped launch the field of volcanology. And its sound remained unrivaled until earlier this year, when an underwater volcano in the Pacific island nation of Tonga erupted violently, also sending a shockwave around the world.

In this episode of Endless Thread, we explore the online fascination with Krakatau, and volcanologists help us try to recreate the cacophonous sound of its 1883 eruption.

Show notes

Full Transcript:

This content was originally created for audio. The transcript has been edited from our original script for clarity. Heads up that some elements (i.e. music, sound effects, tone) are harder to translate to text. 

Ben Brock Johnson: This is a story about a sound.

[Low rumble.]

We can’t hear it, really, because the instruments that recorded it when it happened in 1883 were rudimentary. But they still registered it. Because it was so massive, so complete, that it changed the atmosphere across the planet.

Monique Morgan: The effects that were measured the farthest have to do with airwaves.

Dean Russell: Since then, scientists around the planet have tried to recreate it from the original instrument readings.

Monique: It was recorded by every working barograph on the planet, and some of them recorded the airwaves circling the Earth seven different times.

Ben: The atmospheric shock wave recorded by these barographs lasted for five days. If you sped the recording up, it might have sounded like this:

[Low rumble rises in pitch and explodes.]

Dean: But when it happened, it was lower and deeper.

[Low rumble returns and detunes out of audible range.]

Milton Garces: The dominant sound drops in pitch below what we consider to be audible sound.

Ben: Humans can generally hear a spectrum that starts around 20,000 Hertz (Hz), which sounds like this.

[20 kHz tone.]

For many, this frequency may be inaudible. Here’s 15,000.

[15 kHz tone.]


[10 kHz tone.]

5,000 Hertz.

[5 kHz tone.]

Here’s 1,000.

[1 kHz tone.]


[500 Hz tone.]

Here’s 60 Hertz.

[60 Hz tone.]

When you start getting below this zone, you stop being able to hear the sound.

The sound we’re talking about at its natural state was in many places too deep for human hearing. But the sound was definitely there.

Even if your body can’t perceive parts of the sound, it will be here the whole time because that’s how it was when it first ripped through the atmosphere — a relentless explosion, a fathomless orchestra that was both existentially loud and inconceivably deep.

Milton: It's accessible to us through a sense of vibration, palpitation. But it's not accessible to us as an aural perception of sound.

Dean: This palpitating sound was powerful enough to be felt and heard across thousands of miles.

Ben: The relentless explosion had an aftermath that would last years. And an expedition would eventually set out from over 7,000 miles away — from one end of the Earth, to the other — to figure out what had happened. Much of what we know now are details collected on that expedition — what was found.

Dean: But it was more than just a sound. It marked a special moment in the evolution of human civilization.

Monique: It was a global event that happened just when there was the technology available for it to become a global media sensation as well.

Milton: We had the telegraph network, and we had this early generation global network of pressure sensors. The information came through the early internet.

[Morse code tones.]

Ben: The “early internet,” as in a network of cables making fast transfer of information possible. It was a moment in which the whole Earth witnessed something almost simultaneously. A moment in sound not even slightly rivaled for over a century — until earlier this year.

[2022 explosions from several first-person recordings.]

But the original is tough to beat.

[1883 explosion recreation returns.]

Monique: People who were directly experiencing it really did think it was the end of the world.

Ben: I’m Ben Brock Johnson with producer Dean Russell, and you’re listening to Endless Thread.

Dean: We’re coming to you from WBUR, Boston’s NPR station.

Today’s episode:

Ben: “The Loudest Sound.”

The story of this sound pops up on Reddit constantly in threads with thousands of upvotes. It spans a network of Wikipedia pages. There are full-on Youtube rabbit holes about it, with fights over technicalities in the comments.

Dean: Ever since Ben pitched this story, the two of us have been consumed, which is not all that surprising because this is a sound that has been fascinating to a lot of people for a long time.

Monique: I'm Monique Morgan. I'm a professor of English at Indiana University.

Oliver Lamb: My name's Oliver Lamb. I'm a geophysicist, and I'm originally from mid-Wales.

Janine Krippner: I am Dr. Janine Krippner. I am an associate honorary researcher at the University of Waikato.

Milton: My name is Milton Garces, and I am the director of the Infrasound Laboratory of the University of Hawaii.

Ben: I'm looking at something that's describing the different sources of infrasound, and the list is: supersonic aircraft; rocket launches; explosive volcanoes; nuclear and chemical explosions; aurora, which was a surprising one to me; avalanches; microbaroms; earthquakes?

Milton: We call it the Infrasound Zoo. It is a madhouse. And it's always something blowing up somewhere.

Ben: Is that the infrasound recorder’s mantra? “There's always something blowing up somewhere.”

Milton: That's just my personal one, really. (Laughs.)

Ben: Milton’s search for performances of fathomless orchestras often sends him to volcanoes.

Milton: We record the sound from volcanoes with microphones of all types. In the case of really large eruptions, we can record with regular barometers — instruments that are designed to record daily oscillations at scales of days. Because volcanoes are so diverse in the sound they produce, we can go down to very, very deep periods — way below what you consider sound — and up to very high frequencies where we can record them. And not only record them but listen to them.

[Milton Garces' "Msh 0503090120 200x eruption" recording.]

[Milton Garces' "Msh 0501161100 200x aseismic eruption" recording.]

Dean: There are a lot of ways to record volcanoes and a lot of volcanic sounds. One way or another, you have to place the microphone. And as any decent sound engineer knows, getting the mic close is crucial.

Milton: I almost got killed once because most of the air around me turned into carbon dioxide instead of oxygen.

Ben: Woah.

Milton: Yeah. You don't realize until you try to breathe, and it's like, “Oh, there's no oxygen here. There's no nitrogen left over.” Fortunately, I was in a car, so I could drive off very quickly while holding my breath. But that can happen quickly too.

Ben: Milton says the importance of recordings of sound you effectively can’t hear hasn’t been recognized until recently. But infrasound has always been there. And the process for capturing it has always just been a matter of having the right instruments.

Dean: In 1883, the instruments that picked up this massive sound weren’t designed to capture audible sound, which is created by tiny pressure changes — air compressions that alternate between 20 and 20,000 times per second. These first instruments instead captured longer, large-scale shifts in atmospheric pressure. They were called barographs.

Ben: The more commonly known instrument is a barometer, which looks like a clock face and measures the current atmospheric pressure. Barographs use a cylinder with an arm that draws, showing the pressure changes over time. And on August 26, 1883, barographs around the world started scribbling.

[Explosion sound.]

Oliver: The way that the sound traveled around the world at least four times and how it was recorded in places as far away as London — ever since I knew about that fact, it's just blown my mind.

Dean: Geophysicist Oliver Lamb is describing what essentially was a series of shock waves. Different instruments picked it up in different ways. Some just measured initial waves, of which there were four. Others logged more than that.

Ben: Imagine these waves as atmospheric ripples. In a pond, they would peter out upon hitting the shore. But on a globe, they would just keep going or hit themselves and reflect back. In 1883, some barographs recorded four waves, some recorded seven. Whatever the case, the explosion — or set of explosions — was huge.

[Report from Rodrigues: Several times during the night of the 26th–27th, reports were heard coming from the eastward …]

Ben: This was a witness account.

[Report from Rodrigues: … like the distant roars of heavy guns …]

Ben: It came from the British-controlled island of Rodrigues, off the eastern coast of Africa, 3,000 miles from the origin of the sound, which was discovered later.

Dean: A lot of what we know about this fathomless orchestra was gathered in the aftermath by an organization based all the way in London, where some of the barograph readings were picked up 7,000 miles away.

Ben: A prominent scientific organization called The British Royal Society. It sounds like it’s out of historical adventure literature as well as real life, and its members over the years included Sir Isaac Newton, Charles Darwin, and Stephen Hawking. In 1884, The Royal Society was focused on this one sound.

Monique: They collected a huge amount of data, partly with the public's help. They put an ad in the London Times newspaper in February 1884 asking for authenticated facts related to all sorts of phenomena that they listed. And then, they spent about two years analyzing the data and writing up a massive report, which was published in 1888.

Ben: In the very beginning, 1883, people around the world didn’t know what the hell had happened. But as the impacts lingered for days, months, and years, and as these reports from The Royal Society came in — the facts, the blast radius — they were difficult to even comprehend.

Monique: Some estimates claim that the force of the explosion — just the sheer power of it — was roughly equivalent to, I believe, 10,000 atomic bombs. It was huge.

Dean: What people would discover in jaw-dropping reports that came from various places inside that radius was that the sound was an eruption of awesome proportions.

Ben: The origin point of the radius was a little-known set of islands with a name that you can find everywhere across the internet now — not just because of what happened but also because it happened in this moment when the globe was starting to be connected in a powerful way for the first time.

Monique: A telegram sent at noon on that day, just two hours after the largest of the eruptions, reported: “Sarang in total darkness all morning; stones falling; village near Anjer washed away. … Fear a calamity; there several bridges destroyed, rivers having overflowed through rush sea inland.”

Ben: The name of the origin of this sound was Krakatoa.

Dean: How did it look, smell, sound, feel for the people who witnessed it? More in a minute.


Ben: Let’s start again with a correction.

Janine: Not Krakatoa. Krakatau. So, it's A-U at the end, not O-A. That was a misspelling that came about after the 1883 eruption.

Ben: Whether you call it Krakatoa or Krakatau, we’re talking about three islands in Indonesia, about halfway along the crescent of islands that form the country...

Janine: ...Which is northwest of Australia. And we're in the Sunda Strait, which is between the islands of Sumatra and Java.

Dean: As a New Zealand volcanologist who is currently studying a mountain best known as Mount Doom from Lord of The Rings, Janine gets a lot of questions that are a bit off-topic. Namely from Ben, who really just was curious about Peter Jackson’s depictions of volcanoes in the Rings movies.

Ben: I mean, I had to ask.

Janine: It wasn't bad, although — yeah. We'll stick with that.

Ben: (Laughs.) No, let's hear your criticism.

Janine: Gollum wouldn't have slowly sunk into the lava like he did, but that's a minor detail.

Ben: Oh...

[Ring sound. Lava splash. Gollum screams.]

Ben: This is because liquid rock is heavier than people, so Gollum would have floated as he, you know, burst into flames.

Dean: But back to the real world. In August of 1883, volcanologists like Janine didn’t exist yet. She says the world was about to have a reason for them.

Janine: Because the telegraph lines were recently installed around the world. And so, the news of this eruption traveled the world pretty quickly.

Milton: And people could actually travel there by ship and study the eruption years afterwards. And so, it was kind of like the beginning of volcanology.

Dean: Looking back over a century, it’s easy to understand this technological moment Milton and Janine are talking about as something that allowed the world to experience and understand the same thing all at the same time.

Ben: But when you get closer to it and slow down the time scale a bit, the journey of this fathomless orchestra has a lot of powerful details that took a long time to collect.

[Low rumble.]

Janine: We have eruptions all the time around the world, but usually, they're not heard across multiple countries. So, in order for that to happen, they must have been something really big, really fast.

Dean: Krakatau’s most famous and catastrophic eruptions were big and fast. But they were really the finale of a performance that had started a full three months earlier with low rumbles felt as far away as Australia, where people perceived Krakatau’s activity as earthquakes. But closer to the volcano, Milton says a more complex timbre was emerging.

Milton: So one of the first things you start hearing: the higher frequencies. And you start recognizing that some of the gassing sound is above what you would expect for a typical day out at sea.

[Gassing sounds.]

Ben: A lot of the reports on what would eventually happen were actually reports from ships out to sea and people looking for ships out to sea. Because the point is, if you were within a hundred miles of this place in the years, months, and days running up to the main event, there’s a good chance you were on a boat.

Dean: That's because the Sunda Strait was used for centuries as an important shipping route connecting the Java Sea with the Indian Ocean. The Dutch East India Company used it to access the spice islands, which they colonized and extracted millions and millions of dollars from in the form of spices like nutmeg.

Ben: That was mostly in the 17th and 18th centuries. In the 19th century, during the volcanic activity, there were still a lot of boats going through the strait.

Oliver: And a lot of the activity would have been actually happening underwater. There would be a lot of things impacting the water. There would be a lot of shaking of the water around the island. And I think this — what we call the hydroacoustic waves — would have been traveling from Krakatoa to Singapore and disturbing the telephone lines to the point where it's creating noise that's overwhelming people's voices.

[Low rumble. Underwater waves.]

Dean: This is Oliver again, whose connection to inaudible infrasound and hydroacoustic waves is perhaps linked with something we didn’t understand until we spoke to him.

Ben: Do you have a favorite volcano sound?

Oliver: It's kind of an awkward question to ask me because I'm actually hard of hearing in both ears. So I can't really hear that much when I'm at the volcano itself.

Ben: Do you have a favorite volcano feeling?

Oliver: A feeling of being safe when a volcano is erupting.

Ben: Oliver’s been volcano-obsessed ever since he visited the U.S. and Mount St. Helens in Washington State as a kid. And Krakatau, he says, most volcanologists are obsessed with.

Oliver: It's a once-in-a-century event, once-in-a-millennia event. So nobody in these furthest distances would have realized that the sound would have been coming from a volcano because it's just not feasible to them.

Dean: By 2 p.m. on the 26th of August, the eruption’s massive black cloud of ash was 17 miles high. It would eventually reach 50 miles up into the mesosphere.

By the end of the event, four massive explosions would cause most of the largest of these three islands to completely disappear.

[Four explosions.]

Ben: And the loudest sound ever recorded had legs. But it sounds different depending on where you were on that sound journey, according to Oliver.

Oliver: The thing you have to remember about sound is that as it travels to the atmosphere, the atmosphere kind of filters out the higher frequencies, and the lower frequencies keep traveling.

[Noise filters out high tones.]

Janine: So when we get to the 26th and the 27th of August, we start getting these really big eruption pulses, so much more magma coming out at much faster rates, and it's much more explosive.

Dean: The reports collected by The Royal Society, including that report from Rodrigues Island 3,000 miles away, often spoke of cannon or gunfire, which Milton connects to the technology available at the time.

Milton: It is interesting how the descriptions of sound matches the technology available at the time. Most of the explosions that humans have heard up to there were from low explosives, gunpowder.

Ben: One of the fascinating parts of this to me was the fact that these heavy guns or cannons on ships weren’t always used for firing at other ships. They were used as cries for help. Before flare guns, they just used cannons.

Monique: In some cases, people thought that there was a ship nearby that was firing its large guns to signal that it was in distress. So in many instances, people sent out rescue boats looking for a ship in distress because they thought these sounds were the gunfire of an S.O.S.

Ben: Woah.

Monique: There were ships that were about 900 miles away that described the sounds as thunder without any lightning.

[Distant thundering rumbles.]

Oliver: Some of the places people are hearing it from — Singapore or Jakarta — they would not have thought he was a volcano. They would have thought he was somebody attacking them, or they would have thought he was, like you said, like a lightning storm coming in.

Dean: The closer you got, the more constant the sound was. But it wasn’t organized or the same. It was a cacophony.

Milton: It's this constant rumble, right? That roaring sound. And on top of that are these explosions, right? These events that are distinct in time. You can think of those explosions as fluctuations in the flow conditions; That choke flow, for example, it collects enough, and then it gets trapped, and then it releases very suddenly, right?

Ben: When there’s a sudden release, the result can be a tsunami. Or even multiple tsunamis. And the Krakatau tsunamis were between 100 feet and 135 feet tall. Five hundred miles from the eruption, Monique says those tsunamis did a ton of damage.

Monique: Yeah, it’s just mind-blowing. It’s staggering. It’s difficult to imagine. There was an instance where there was a steamship that was carried by one of these huge waves almost two miles inland in Sumatra and stranded 60 feet above sea level. And, yeah, there are some really horrifying eyewitness accounts of people fleeing inland, fleeing uphill, climbing palm trees, trying to escape the incredibly large tsunamis.

[Large waves.]

Dean: The walls in Sumatra homes shook and shuddered. And outdoors, that shuddering was present, too.

Milton: You know, when you're driving, and somebody opens the back window, and you get that Helmholtz resonance inside the car.

Ben: Oh yeah. That dh-dh-dh-dh. That kind of deal?

[Helmholtz resonance.]

Milton: Yeah. That. You can get that out there in the wild, and it's not a good feeling, and there's no window you can raise up again, right?

Ben: So it would just be everywhere around you? That's crazy.

Milton: Oh yeah. It's—. You know, because it's being produced, it’s being radiated, right?

Ben: Again, a lot of the sound here has to do with the pressure and the kind of pressure and lava that was present at Krakatau.

Janine: If you think of a bottle of coke or beer or champagne before you open it, you don't see the bubbles, right? The gas is within the liquid. So magma is kind of like that. When it's way down below the surface, it has all this gas within it. And when you release the pressure, like opening the cap of the bottle, that gas can start to come out and form bubbles.

Dean: For volcanoes like Hawaii’s Kīlauea, which erupts slowly over a period of months and years, those volcanoes produce runny lava. The gas releases quickly and continuously …

Janine: … but when we have sticky magmas, the gas can't escape as quickly. So you get it going up to the surface. The gasses will need to come out. You have all these bubbles forming within it, and it gets to a point where all of that explodes. So now it's like shaking up that bottle of coke and taking the cap off.

[Pyroclastic flows.]

Dean: This intense and sudden release creates pyroclastic flows — huge mixtures of rock and ash and gas over a thousand degrees Fahrenheit that race across the landscape, destroying nearly everything in their paths.

Milton: When you're on a boat, it's a noisy environment. If you're on a sailboat, which is most likely what they had, then you still get a lot of hull noise and ocean noise coming in. You have surf noise, too, right? Because the ocean is always making sound.

[Ocean sounds and gulls.]

Oliver: So we've got the pyroclastic density currents that might be coming down the side of the volcano. And that can add a deep rumbling noise, lots of crackling noise. Rocks inside are crashing into each other. But in the case of Krakatoa, because it's quite close to water, you might hear the quite intense noise of interaction of hot rocks with water. So this might include steam explosions.

[Steam explosions.]

Oliver: You might also hear some very distinct loud splashing noises, huge rocks from the explosion impact with the water. That would then just sort of taper out as everything settles down. If you were there in person, you would hear a sort of pitter-patter of ashfall around you.


Ben: In some cases, that pitter-patter turned to a downpour.

Monique: A ship named Norham Castle was 40 miles from Krakatoa during the eruptions, and the captain claimed, “So violent are the explosions that the ear-drums of over half my crew have been shattered.”

Ben: Wow.

Monique: But the most harrowing accounts of this were definitely the people who were closest to the eruption, including people who were on board ships that were trying to sail in this region. So there was a British ship that was only ten miles south of Krakatoa during the earlier eruptions on August 26, the day before the biggest explosions. He described fast-moving clouds, noise like artillery, large pieces of pumice, of volcanic rock raining down on the ship overnight. He said he saw, “Chains of fire appeared to ascend and descend between it and the sky … there seemed to be a continued roll of balls of white fire" traveling down the mountain. Presumably, that was lava. The air was hot and choking sulfurous. So it really does sound hellish.

Dean: Not only did the area around the volcano sound hellish and smell hellish, when you combine volcanic material with ocean water, especially at a huge scale, it can produce massive amounts of hydrochloric acid.

On a ship 90 miles from the eruption, Monique says a first officer wrote a chilling entry into the logbook.

Monique: “It was darker than any night I ever saw; this was midnight at noon, a heavy shower of ashes came with the squall, the air being so thick it was difficult to breathe, also noticed a strong smell of sulphur, all hands expecting to be suffocated; the terrible noises from the volcano, the sky filled with forked lightning, running in all directions and making the darkness more intense than ever; the howling of the wind through the rigging formed one of the wildest and most awful scenes imaginable, one that will never be forgotten by anyone on board, all expecting that the last days of the Earth had come.”

Ben: It’s easy to understand why. One account from a ship described burning pumice rocks four inches in diameter pelting the deck. Another, a downpour of mud that became six inches deep on the surface of the ship in about 10 minutes.

It was all part of these explosions throwing material through the air, creating atmospheric shockwaves and underwater shockwaves.

Janine: I'm talking like cubic kilometers of material coming out explosively into the water. That triggered a tsunami. But the pyroclastic flows also continued to flow over the water for at least, I think it was at least 60 kilometers.

Dean: If you were really close to the explosion, something eerie happened that would leave you incredulous — perhaps a short time before you died. You didn’t actually hear anything.

Oliver: Now we're talking about the strange phenomenon of the acoustic shadow zone. So this is—. You know, one thing to know about how sound travels through the atmosphere is that it wants to bend upwards. And so, this means that when the sound gets at this point, it actually starts bending back towards the ground again. So what this means is it goes back towards the ground. The people further away might hear sounds that people closer to the volcano would not have heard.

Ben: Wow, there’s like a folding tidal wave of sound that might miss people who are closer?

Oliver: Exactly. Absolutely. This is pretty well-documented phenomenon from things like nuclear explosions and from previous volcanic eruptions like Mount St. Helens.

Ben: Think about it. Most volcanoes point up. And the explosions of sound would, in some ways, take a similar path to the lava: up first, then out, then back down and across where the material — the tsunamis, the atmospheric shockwaves — all reached all the ships navigating through the strait.

Monique: In the days and weeks afterwards, any vessels that were trying to sail through the Sunda Strait near Krakatoa would just have to sail through huge chunks of pumice. And at that time, many of them were actually carrying dead bodies, human remains.

Dean: There’s a photo from the beach of Java, 20 miles off, showing a piece of coral that was hurled through the air. A man in a white suit and a cane stands next to it. It’s the size of a house.

It’s things like this and the pumice and the pyroclastic flows and, most of all, the tsunamis caused by Krakatau that made it one of the most devastating volcanic eruptions in history. Roughly 36,000 people died, most from Java and Sumatra.

Ben: These are the kinds of details that would come in bits and pieces, starting with telegrams in late August, news reports that were up to the day and minute but would join a slower realization around the world that not only had this massive eruption happened but that its impact was far beyond the initial reports. For the next year, a huge portion of the planet was seeing these after-effects.

[Low rumble returns.]

Monique: Nearly the entire globe experienced these really vivid red sunsets in the months after the eruption. You know, Western Europe, the United States, Canada. One of the earliest accounts was from Honolulu.

Dean: People studying Krakatau are still discovering the volcano’s impact at the time. In 2004, an astronomer posited that the red sky in the background of Edvard Munch’s famous painting “The Scream” from 1893 shows Krakatau’s long reach into the sky over Norway.

Ben: Aerosols sent into the air may have dimmed the sun, reducing the global temperature at the time by 1.2 degrees Celsius, which is insane to think about. Humanity is currently trying to stop the march of climate change by preventing a rise in global temperature between 1.5 degrees and 3 degrees Celsius, which scientists believe will be catastrophic. Krakatau cooled the planet in one eruption event.

All of this mind-bending impact led to the global effort to gather facts.

Oliver: And not just in human history, but in scientific history as well, because it really launched volcanology as we know it.

Dean: Along with creating the study of volcanoes, it prompted the discovery of aspects of our world and our climate that are crucial to our modern understanding of the interconnected nature of our planetary existence.

Monique: It was actually the Krakatoa eruption and the study of it that is sometimes credited with people basically discovering the jet stream and understanding currents in the upper atmosphere. It was tracking the particles, and the effects that it had on the way the sunset looked that led people to understand how the material erupted from Krakatoa was circling the globe and in what direction, and at exactly what speed. They figured out it was 73 miles an hour.

Dean: This loudest sound with all of its great and terrible effects was unparalleled for a century until this past January, when an underwater volcano in the Pacific island nation of Tonga erupted violently, spawning a tsunami that devastated many of its islands and troubled shores across the ocean. At least six people died — not 36,000, but six — which may, in part, show how much benefit the study of volcanology has brought to the world. And how much room it has to grow.

The infrasonic shock wave from Tonga, which is still being studied and will still be studied for years to come, rippled through the Earth for days.

[Boise State’s infrasonic recording of the Hunga Tonga-Hunga Ha'apai eruption.]

Ben: It’s easy to look back at Krakatau — the facts and Youtube videos about it posted across the internet — read the reports from The Royal Society and say, “Whew, that sounds rough.” But it’s helping us watch for and react to modern natural disasters.

Janine: We have volcano monitoring. We have volcanologists around the world working on every aspect of volcanoes, from the magma, how it forms below the surface, how it erupts, what that does. How do we communicate what that does so we can help people? How do we work with emergency managers and decision-makers so that we can prevent people from being in the dangerous areas? We have people working on, How do you best make a map that shows people where not to be and where to evacuate? So it's been this constant process of learning how we help people in every part of our field that is going towards that bigger goal.

Dean: Krakatau was also this incredible moment of global connectedness of a massively viral event that we take for granted now …

[1883 explosion recreation returns.]

Ben: … when everyone paused for a moment and said, “What. The heck. Was that?” And we started to listen and learn from each other more about the answer.


Dean: Endless Thread is a production of WBUR in Boston.

Want early tickets to events, swag, bonus content? Ben’s fathomless orchestra, my pyroclastic flows, join our email list. You’ll find it at

This episode was written and hosted by Ben Brock Johnson, who mysteriously forgot to send his audio file containing the credits before disappearing into an all-day meeting.

And this episode was produced by me, Dean Russell. Amory Sivertson will be back next week. Mix, sound design, and music composition for this episode by Paul Vaitkus, a man who took Ben and my strange, vague and passionate verbal descriptions and ran with it.

Editing help from Jeb Sharp. Our web producer is Megan Cattel. The rest of our team is Nora Saks, Quincy Walters, and Grace Tatter.

Endless Thread is a show about the blurred lines between digital communities and the loudest sound ever recorded. If you’ve got an untold history, an unsolved mystery, or a wild story from the internet that you want us to tell, hit us up. Email

Headshot of Ben Brock Johnson

Ben Brock Johnson Executive Producer, Podcasts
Ben Brock Johnson is the executive producer of podcasts at WBUR and co-host of the podcast Endless Thread.


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Dean Russell Producer, WBUR Podcasts
Dean Russell is a producer for WBUR Podcasts.



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