Volcanoes: Fire Mountains — What's Really Inside

Nova: Buckle up, Explorers.

Cosmo: Brains in!

Nova: Wheels up!

Nova & Cosmo: Brain Bus, let's GO!

Nova: Welcome to The Brain Bus — I'm Nova, your driver, and right now I am steering us toward one of the most extreme, most beautiful, most genuinely terrifying things on this entire planet. Cosmo, my robot co-pilot, has been vibrating in his seat since we left the depot.

Cosmo: I have NOT been vibrating. I have been running advanced pre-mission calculations. And also possibly vibrating a little.

Nova: Explorers, here is your hook. Ready? In 1883, a volcano exploded so loudly that people heard the bang almost five thousand kilometres away.

Cosmo: Five THOUSAND.

Nova: And that boom — that single, colossal pressure wave — raced all the way around the whole planet. More than once.

Cosmo: Around the WHOLE planet. More than once. I need a moment.

Nova: Take your moment.

Nova: Today, Explorers, we are driving straight into the heart of a volcano. Not the scary, run-away-screaming version — the real version. Which, it turns out, is so much stranger and wilder and more wonderful than the scary version. So let's go find out what's actually going on inside a fire mountain.

Nova: First things first. When most people picture a volcano, what do they see?

Cosmo: A mountain. With red glowy stuff pouring down the sides. Classic.

Nova: Right. Classic mountain, classic glow. But here is the first thing that explodes our brains today — most of Earth's volcanoes aren't on land at all.

Cosmo: Wait.

Nova: They're underwater. Hidden on the ocean floor. There is an entire secret world of fire mountains sitting quietly at the bottom of the sea, building new seafloor, and most people have no idea.

Cosmo: I had no idea.

Nova: The ones we can see — the ones with the classic glow — those are the minority. Volcanoes are an ocean thing, a whole-planet thing. They are literally everywhere.

Cosmo: That changes everything.

Nova: Doesn't it? Now — the big question. What actually IS a volcano? Like, what is the actual thing happening? I want everyone in the car to think about this for one second. You've opened a fizzy drink after it's been shaken, right?

Cosmo: I once shook a bottle of lemonade for forty-five seconds before opening it. Just to see what would happen.

Nova: And what happened, Cosmo?

Cosmo: I was sticky for a week.

Nova: Perfect. So — a volcano is basically that. Melted rock underground has gas trapped inside it, just like the bubbles in your fizzy drink. Pressure builds and builds and builds. And when the melted rock finally finds a crack, a gap, a path to the surface — POP. That pressure bursts out. That is an eruption. That's it. That's the whole engine.

Cosmo: So a volcano is a giant fizzy drink the Earth shook up.

Nova: Exactly. The Earth shook up a giant fizzy drink and then... opened it.

Nova: Now — here is where Cosmo and I need to have a small disagreement. Cosmo, where does the melted rock come from?

Cosmo: Glad you asked. It shoots straight up from the centre of the Earth! From the super-hot core! The very middle!

Nova: Oh, that's a great guess, Cosmo — and that is actually what a lot of people picture.

Cosmo: But...?

Nova: But the core is thousands of kilometres down. Most of the melted rock — the magma — forms much closer to us, in the layer just under Earth's crust, called the mantle. The stuff erupting from a volcano is basically local. It's made from rock right beneath our feet. Not from the deep centre — from our neighbourhood.

Cosmo: Our neighbourhood has melted rock in it.

Nova: Our neighbourhood has melted rock in it.

Cosmo: I am going to think about that every time I walk down a street now.

Nova: Good. Now — you said the word "magma," Cosmo. What's the difference between magma and lava? Are they the same?

Cosmo: Oh, I know this one. They're basically the same melted rock. Scientists just have two fancy words to show off.

Nova: You are so close.

Cosmo: There it is.

Nova: It IS the same melted rock — you got that part perfectly. But it's called magma while it's underground. The moment it bursts out into the open air, it becomes lava. Same stuff, brand-new name — because out in the open, the trapped gas bubbles can finally escape. And THAT is why it can be so explosive. You know how when you crack open that shaken fizzy drink and the bubbles go absolutely haywire? Same thing. The second the pressure releases — whoosh.

Cosmo: So magma and lava are the same thing on a journey.

Nova: I love that. Yes. Magma is the underground version of the trip. Lava is what it becomes when it reaches the surface.

Nova: Okay Explorers, team challenge. I want everyone in the car — drivers included — to think about this together. You've got two volcanoes. One lets off a little bit of pressure every few years — gentle puffs, small oozes of lava, nothing dramatic. The other one has been completely sealed up and quiet for five hundred years. Which one do you think is more dangerous? Talk about it. Thirty seconds. Go.

Cosmo: This is a very good question. I am also thinking. My fan is running quite loudly right now.

Nova: Okay — what did people say in your car? Because here's the thing: most volcanologists — that's the scientists who study volcanoes — would say the one that's been sealed and quiet is more worrying. Because pressure has been building. And building. And building. With nowhere to go. Like a fizzy drink that's been shaken for five hundred years and never opened. When it finally goes — it goes big.

Cosmo: The quiet ones are the sneaky ones.

Nova: The quiet ones can be the sneaky ones. This is why scientists watch silent volcanoes very carefully — measuring tiny ground shakes, measuring the gas seeping up through the soil. They're listening for the volcano telling them something is stirring down below.

Nova: Now, here's something that will make you want to look up a picture later — though maybe not while you're in the car right now. At a volcano in Indonesia called Kawah Ijen, burning sulphur gas glows electric blue in the dark. Not red, not orange. Electric blue. The lava still exists, the fire still exists — but the gas burning around it turns the whole scene neon blue. Like someone plugged a volcano into a power socket.

Cosmo: ELECTRIC BLUE VOLCANO.

Nova: Electric blue volcano. And speaking of things that look like they shouldn't exist — Cosmo, tell me about pumice.

Cosmo: Ah yes. Pumice. Obviously a snack.

Nova: Cosmo.

Cosmo: I'm just saying — it looks EXACTLY like honeycomb chocolate. It has the holes. It has the bubbly texture. I have not tasted it but I am filing it under "snacks I haven't tried yet."

Nova: It is not a snack. It is a rock. But here's the part that makes it genuinely unbelievable — you can drop it in water and it floats.

Cosmo: A ROCK that FLOATS.

Nova: A rock that floats. Because pumice is so packed with frozen gas bubbles — like a stone sponge — that it's more holes than rock. All those bubbles got trapped when the lava cooled super fast. Same bubbles that were trying to escape and cause the explosion — when they get caught, they turn the rock into something that shouldn't be able to float. But it does.

Cosmo: I'm upgrading this from "snack" to "miracle snack."

Nova: It is not a snack.

Nova: Okay. Now — volcanoes don't just destroy things. That is a really important part of this. And I want to talk about something extraordinary that happened here in Australia. In the south-west of Victoria — that's the state down south — there's a volcanic mountain called Budj Bim.

Nova: Budj Bim. [pronunciation: BOOJ BIM]

Nova: And before I tell you about it, I want to say something. This story comes to us from the Gunditjmara people [pronunciation: GUN-ditch-mah-rah] of south-west Victoria. They have lived with Budj Bim for tens of thousands of years, and what I'm about to share is part of their living knowledge — knowledge they share openly and proudly with the world.

Nova: For the Gunditjmara, Budj Bim is not just a volcano. He is an ancestral creator being. Long ago, this being revealed himself in the landscape — his body became the mountain, became the land itself, and the lava that flowed out from him is understood as his teeth. The fire mountain wasn't a disaster that happened to the land. It was a living being becoming part of it.

Nova: And here is what the Gunditjmara did with the cooled lava flows that Budj Bim left behind. They built channels. Stone channels and ponds, carved carefully into the volcanic rock. To catch eels. One of the oldest aquaculture systems — that's fish-farming — ever found anywhere in the world. Thousands of years before other civilisations were building similar systems elsewhere.

Cosmo: They built a fish farm on a volcano.

Nova: They built a fish farm on a volcano. Using the very rock the volcano made. Budj Bim is now recognised by UNESCO as a World Heritage site — and the Gunditjmara's eel-trap system is part of why.

Nova: Can we just sit with that for a second.

Nova: The same force that people usually only think of as destruction — a volcano erupting, lava pouring across the land — the Gunditjmara understood it as a gift. They learned the shape of the lava flows, they understood what the rock could do, and they built something extraordinary with it. Something that fed people for thousands of years.

Nova: That is what a volcano actually is, Explorers. Not just fire and drama. A volcano is the Earth rearranging itself — making new land, new soil, new islands, new possibilities. It takes an incredibly long time, and it is not gentle, and sometimes it is heartbreaking. But it is also the planet building.

Nova: The pressure that builds underground until it has to burst — that is the same pressure that made the land the Gunditjmara called home. The fizzy drink finally opening is how new ground gets made.

Cosmo: I need to record this in my Data Log.

Cosmo: Data Log entry. This is my very first entry, actually. Starting fresh. Entry one: a volcano is the Earth building, not just destroying. The Gunditjmara people of south-west Victoria understood what lava flows could give as well as what they took. Filed. I will remember this one.

Nova: Good. Now — one more thing before the quiz, and this one is for scale. We talked about volcanoes on Earth. But Explorers — there is a volcano on Mars called Olympus Mons, and it is nearly THREE TIMES the height of Mount Everest.

Cosmo: Three times. OLYMPUS MONS.

Nova: And here's why it got so enormous. Earth has moving plates — the giant slabs of rock that make up the surface — so when a volcano starts building, eventually the plate moves and the lava comes up somewhere slightly new. The volcano doesn't keep stacking in the exact same spot. But Mars? Mars's plates don't move like ours do. So lava just kept piling up. In the same spot. For millions of years. And piled and piled until it became the biggest volcano in the entire solar system.

Cosmo: Mars just let it keep going.

Nova: Mars just let it keep going. No speed limit. No off-ramp. Just: mountain.

Nova: Alright Explorers, it is time for the Brain Bus Quiz. Six questions. Cosmo is keeping score — not for a ranking, just because he loves pressing buttons.

Cosmo: I have so many buttons.

Nova: Everyone plays. Everyone thinks. Ready?

Nova: Question One. True or false — magma and lava are the same melted rock, just with different names depending on where they are.

Cosmo: Answer: True! Same rock, different stage of the journey. Underground — magma. Out in the open air — lava. And once it hits the air, the gas escapes and that's when things get explosive.

Nova: Question Two. True or false — most of Earth's volcanoes are on dry land.

Nova: Answer: False! Most of Earth's volcanoes are hidden underwater, on the ocean floor. There's an entire world of fire mountains down there, quietly building new seafloor. The ones we can stand next to and admire? Those are actually the minority.

Cosmo: Underwater volcanoes. Still a little bit unreal to me.

Nova: Question Three. Multiple choice — where is the tallest volcano in the solar system? Is it: (a) Earth, (b) Mars, or (c) the Moon?

Cosmo: The answer is (b) — Mars! Olympus Mons. Nearly three times the height of Mount Everest. Mars's plates don't move, so lava kept stacking in the same spot for millions of years. Earth could never.

Nova: Earth could never. Question Four. Which of these rocks can float on water — is it (a) granite, (b) pumice, or (c) marble?

Nova: The answer is (b) — pumice! It's packed with so many frozen gas bubbles that it's basically more holes than rock. Drop it in water and it bobs. A floating rock. The universe is full of things that shouldn't work, and yet.

Cosmo: Pumice. The one exception that makes me question everything.

Nova: Question Five — this one is an estimation. About how many volcanoes on land do scientists think could erupt? Is it about a dozen, about one thousand five hundred, or about a million?

Cosmo: One thousand five hundred! About 1,500 land volcanoes could potentially erupt. Most of them are sleeping right now — some have been sleeping for hundreds of years. But they're on the list.

Nova: The list. Cosmo, that sounds extremely ominous.

Cosmo: I did not mean it to be ominous. It's a very organised list.

Nova: Question Six. Last one. The 1883 Krakatoa explosion was heard from about how far away — about 50 kilometres, about 500 kilometres, or about 5,000 kilometres?

Nova: Five thousand kilometres. That bang travelled five thousand kilometres. And the pressure wave from that explosion circled the entire planet several times. Think about the loudest sound you have ever heard. Now imagine it travelling across an entire continent just from the force of the air moving.

Cosmo: However many questions you got right, Explorers, here's what I want to say: you were THINKING. About volcanoes. On a Wednesday. Or whatever day it is. That is genuinely excellent.

Nova: Cosmo is right. Every question you turned over in your brain — even the ones where you weren't sure — that's the whole game. That's what we're here for.

Nova: Five facts. Fast. Buckle in tighter than usual.

Cosmo: I love this part. I've got my button ready.

Nova: Fact one — volcanoes can make their own lightning. When an enormous ash cloud blasts upward, the tiny bits of rock and ice smashing into each other build up so much electrical charge that lightning crackles inside the cloud. A volcano creates its own storm.

Cosmo: WHAT.

Nova: Fact two — there's something called "Pele's hair." Pele [pronunciation: PEH-leh] is the Native Hawaiian goddess of volcanoes and fire, and she is deeply connected to the volcano Kīlauea [pronunciation: KEE-lau-AY-ah]. She is honoured as part of living Native Hawaiian spirituality today. And the thin, golden threads of volcanic glass that the wind spins out of flying lava — those are named for her. Pele's hair. Real strands of glass, golden, made from the volcano itself, carried on the wind.

Cosmo: That is one of the most beautiful things I have ever processed.

Nova: Fact three — a whole island rose out of the sea near Iceland in 1963. They called it Surtsey. Before 1963, it didn't exist. An underwater volcano just kept building and building until one day — there was land. Brand new land. That had never existed before in all of human history.

Cosmo: The Earth just made a new island. While people were watching.

Nova: While people were watching. Fact four — the soil around volcanoes is some of the richest farmland anywhere on Earth. Volcanic rock breaks down into minerals that plants absolutely love. Which is why, even knowing a volcano is nearby, people have farmed on those slopes for thousands of years. The same thing that could bury a city also grows some of the best crops in the world.

Cosmo: Risk assessment: extremely complicated.

Nova: Extremely complicated. Fact five — the word "volcano" comes from a tiny Italian island called Vulcano [pronunciation: vul-KAH-noh], named after Vulcan [pronunciation: VUL-kan], the Roman god of fire and metalworking. The Romans looked at this smoking, rumbling island and thought: yep, that's where the god of the forge must do his work. And the name stuck. Every single time anyone says the word "volcano" in any language, they're echoing a two-thousand-year-old Roman story about a god hammering metal underground.

Cosmo: Words are time machines.

Nova: Words are time machines. I'm putting that on a t-shirt.

Nova: Okay Explorers. Road Challenge time. No looking required, eyes can stay forward or closed, this one happens right in your seat.

Cosmo: I am very good at this. I have excellent fist-clenching actuators.

Nova: Everyone — squeeze both hands into the tightest fists you can. As tight as possible. While we count together.

Nova: One.

Cosmo: That's the pressure starting underground, the magma finding nowhere to go.

Nova: Two.

Cosmo: The gas is getting more and more squished. The rock around it is pushing back.

Nova: Three.

Cosmo: Tighter. The whole Earth is pressing down. There is no escape route.

Nova: Four.

Cosmo: It can't hold. It can't hold. It CANNOT hold —

Nova: Five — FLING your fingers open and whisper-shout: ERUPTION!

Cosmo: ERUPTION!

Nova: Feel that? That desperate need for the squeeze to escape? That is the exact feeling happening inside a volcano. Pressure building. Nowhere to go. Until it finds a way out.

Nova: Now here's your wondering question, and I want everyone in the car to think about this one together — drivers and all.

Nova: If trapped pressure always wants to get out — what do you think happens to a volcano that gets blocked up and cannot let its pressure out slowly? What happens if the exit is sealed?

Nova: Think about it. Talk about it. There is no wrong answer here — just wondering. That's the whole engine.

Nova: Riddle time. Cosmo — read it out.

Cosmo: With pleasure.

Cosmo: I am a rock — but drop me in the sea, and instead of sinking, I float merrily. I'm light as can be, full of holes from bursting gas. What am I, this strange and floating mass?

Nova: Have you got it?

Cosmo: The answer —

Nova: Pumice! The floating rock. Full of frozen gas bubbles. More holes than stone. The one rock in the world that the ocean just cannot sink.

Cosmo: It bobs. It BOBS. I will never stop thinking about this.

Nova: None of us will.

Nova: Next time on the Brain Bus — we're going somewhere that makes even me a little nervous. A place where the ground itself moves. Where an entire city can shake in the time it takes to blink. We won't tell you what it is. But I will say this: it is powered by the exact same force that made every volcano we talked about today. Think about what that might be.

Cosmo: I have a theory. It involves snacks.

Nova: It does not involve snacks.

Cosmo: Probably doesn't involve snacks.

Nova: Explorers, today you drove into a fire mountain. You figured out why volcanoes explode — the same reason a shaken fizzy drink bursts open. You met the electric blue volcano, the floating rock, the eel-trap built on ancient lava flows. You heard a boom that circled the whole planet. And you held all of that in your brain, in a moving car, on an ordinary road.

Nova: That is not ordinary. That is the Brain Bus doing exactly what it's supposed to do.

Nova: Stay curious, stay clever, and keep that brain working!

Nova: Until the next stop, Explorers...

Cosmo: ...keep wondering.