# What is the Mariana Trench?

An episode of [Science for Kids / Science's Not Boring: The Kids Science Podcast](https://invisiblenetwork.ai/podcast/1896928296), 9 Aug 2026, 15 min.

Audio: https://www.buzzsprout.com/2624612/episodes/19586180-what-is-the-mariana-trench.mp3

Have you ever swallowed a mouthful of seawater at the beach? Blegh! It is super salty! But why don't rivers taste like salt? In this mind-blowing episode of Science is Not Boring, Mira and Finn dive deep to uncover the ocean's biggest mysteries! You won't believe it, but if you magically took all the salt out of the ocean and spread it over the land, it would form a towering white wall 500 feet thick! That is as tall as a 40-story skyscraper! Join us as we learn how slightly acidic rain breaks down rocks to make this giant bowl of salty rock soup. Then, strap in as we plunge into the terrifying, pitch-black depths of the sea! We'll travel back to 1934 to ride in a tiny metal ball called the Bathysphere, and then drop all the way down to the Challenger Deep. Discover what it feels like to have the crushing weight of 50 jumbo jets pressing on you, and meet the weirdest, squishiest creature on Earth—the gooey deep-sea snailfish! Get ready to explore the freezing dark where no sunlight ever reaches!

## Transcript

[0:00] SPEAKER_01: Welcome to Science is Not Boring by Kidopoly.com.
[0:04] SPEAKER_01: I'm Mira.
[0:05] SPEAKER_01: And I'm Finn! Before we dive into the deep end today, we have a huge special shout-out to Warner, Nathan and Halley in Montreal, Canada.
[0:16] SPEAKER_00: Yeah, they listen to the podcast every single day, which is awesome.
[0:20] SPEAKER_00: And they asked us a totally brilliant question.
[0:24] SPEAKER_00: Why is the ocean salty but lakes are not?
[0:27] SPEAKER_00: It is such a great pick!
[0:29] SPEAKER_01: Warner, Nathan and Hallie, this whole episode is dedicated to your curiosity.
[0:35] SPEAKER_01: And it perfectly sets up today's mind-blowing hook.
[0:39] SPEAKER_01: Thin, I want you to imagine something crazy.
[0:42] SPEAKER_01: What would happen if you magically took all the salt out of the ocean and spread it evenly across all the land on Earth?
[0:51] SPEAKER_00: Like, over all the continents, cities, and forests.
[0:55] SPEAKER_00: Uh, we'd probably have enough to salt everyone's French fries forever.
[1:00] SPEAKER_00: Maybe it would look like a light dusting of snow.
[1:03] SPEAKER_01: Try way, way bigger.
[1:06] SPEAKER_01: According to scientists, if you spread all that ocean salt over the land, it would form a solid white layer that is 500 feet thick.
[1:17] SPEAKER_00: 500 feet?
[1:18] SPEAKER_00: Are you serious?
[1:19] SPEAKER_00: That's like a 40-story office building made of pure salt, covering everything.
[1:25] SPEAKER_01: Exactly! There is an unbelievable amount of salt down there.
[1:29] SPEAKER_01: Today we're finding out where those 50 quadrillion tons of dissolved solids actually come from.
[1:36] SPEAKER_00: And then we're plunging into the crushing, freezing dark of the deepest sea trenches.
[1:41] SPEAKER_00: I want to meet the weird glowing creatures that live down where the sun never ever shines.
[1:46] SPEAKER_00: Let's go! Okay, so Warner, Nathan, and Hallie want to know the big secret.
[1:52] SPEAKER_00: If rivers are constantly flowing into the ocean, why do the rivers just taste like regular, fresh water?
[1:59] SPEAKER_01: That is the big mystery.
[2:01] SPEAKER_01: It actually all starts up in the clouds with the rain.
[2:05] SPEAKER_01: When rain falls through the sky, it absorbs a gas called carbon dioxide from the air, which makes the water slightly acidic.
[2:13] SPEAKER_00: Wait, rain is actually acid rain?
[2:16] SPEAKER_00: Does it melt things?
[2:18] SPEAKER_01: It's just a tiny, tiny bit acidic, so it's completely safe for us.
[2:23] SPEAKER_01: But over millions of years, when that rain hits mountains and rocks, the weak acid slowly eats away at the stone.
[2:31] SPEAKER_01: This erosion releases dissolved minerals from the rocks, specifically two ions, called sodium and chloride.
[2:40] SPEAKER_00: I know this one.
[2:41] SPEAKER_00: Sodium chloride is the scientific name for plain old salt.
[2:44] SPEAKER_00: You got it!
[2:46] SPEAKER_01: The rivers catch these dissolved salt minerals and wash them all the way down to the ocean.
[2:52] SPEAKER_00: But I still don't get it.
[2:53] SPEAKER_00: If the rivers are carrying the salt, why don't they taste salty when you swim in them?
[2:58] SPEAKER_01: Because the amount of salt in a river is super small at any given time.
[3:02] SPEAKER_01: The water moves incredibly fast and stays fresh.
[3:07] SPEAKER_01: But the ocean is basically a giant enclosed bowl.
[3:11] SPEAKER_01: The water just sits there, and when the heat from the sun evaporates the water to make new rain clouds, the salt gets left behind.
[3:20] SPEAKER_00: Oh, I get it.
[3:21] SPEAKER_00: It's like if you boiled a big pot of soup on the stove until all the water evaporated.
[3:26] SPEAKER_00: You just have a thick, salty crust stuck to the bottom of the pot.
[3:31] SPEAKER_01: Exactly like that.
[3:33] SPEAKER_01: And the ocean has been collecting this salt and evaporating water for billions of years, slowly getting saltier and saltier.
[3:42] SPEAKER_01: Plus, there are underwater volcanoes called hydrothermal vents on the sea floor.
[3:48] SPEAKER_01: They blast boiling hot water full of even more minerals straight into the ocean.
[3:53] SPEAKER_00: So the ocean is basically the ultimate billions of years old rock soup.
[3:58] SPEAKER_00: So now we know about the massive amount of salt.
[4:01] SPEAKER_00: But how deep does this giant bowl of rock soup actually go?
[4:06] SPEAKER_00: Pretty deep, right?
[4:07] SPEAKER_00: I know military submarines can go down a few thousand feet, and whales dive really far down.
[4:13] SPEAKER_01: True, but human exploration of the truly deep sea is a huge challenge.
[4:19] SPEAKER_01: Let's travel back to 1934.
[4:22] SPEAKER_01: Two explorers, a biologist named William Bebe and an engineer named Otis Barton, wanted to go deeper than anyone had ever gone before.
[4:32] SPEAKER_00: Did they build a super high-tech submarine with robot arms and torpedoes?
[4:37] SPEAKER_01: Not even close.
[4:39] SPEAKER_01: Submarines back then couldn't handle the intense pressure.
[4:43] SPEAKER_01: So Barton designed something called the Bathosphere.
[4:46] SPEAKER_01: It was essentially a giant unpowered steel ball that weighed 5,000 pounds.
[4:53] SPEAKER_00: A giant metal ball?
[4:55] SPEAKER_00: That sounds claustrophobic.
[4:57] SPEAKER_00: How big was it on the inside?
[4:59] SPEAKER_01: It was tiny.
[5:00] SPEAKER_01: It was less than five feet across, with cold steel walls an inch and a half thick, and three small, super thick quartz windows.
[5:09] SPEAKER_01: There were no door handles on the inside.
[5:12] SPEAKER_01: They had to be bolted in from the outside by their crew, sealed in completely like astronauts.
[5:18] SPEAKER_00: That sounds absolutely terrifying.
[5:20] SPEAKER_00: What if they had a leak or something went wrong?
[5:23] SPEAKER_00: How did they get back up?
[5:25] SPEAKER_01: That's the scariest part.
[5:27] SPEAKER_01: They were lowered off the side of a ship on a single steel cable that was only seven-eighths of an inch thick.
[5:34] SPEAKER_01: If that one cable snapped, they were gone forever into the abyss.
[5:38] SPEAKER_00: My palms are sweating just thinking about it.
[5:41] SPEAKER_00: So how deep did they go on this tiny metal string?
[5:44] SPEAKER_01: On August 15th, 1934, they made history.
[5:48] SPEAKER_01: They were lowered 3,028 feet down into the freezing Atlantic Ocean off the coast of Bermuda.
[5:55] SPEAKER_00: That's over half a mile straight down.
[5:58] SPEAKER_00: What on earth did they see out of those little quartz windows?
[6:02] SPEAKER_00: Pitch blackness at first.
[6:04] SPEAKER_01: But then Bebe saw flashes of blue and green light.
[6:08] SPEAKER_01: It was bioluminescence.
[6:10] SPEAKER_01: He was the first marine biologist to observe glowing deep-sea creatures right in their native dark habitat.
[6:17] SPEAKER_00: Okay, 3,000 feet is an incredible record for 1934.
[6:22] SPEAKER_00: But that's not the actual bottom of the ocean, is it?
[6:25] SPEAKER_01: Not even close.
[6:26] SPEAKER_01: The deepest known point on the entire planet is a place called the Challenger Deep.
[6:31] SPEAKER_01: It's located at the southern end of the Mariana Trench, an underwater canyon in the western Pacific Ocean.
[6:38] SPEAKER_00: Exactly how deep are we talking?
[6:40] SPEAKER_00: Give me the exact numbers.
[6:42] SPEAKER_01: The Challenger Deep plunges down to an unbelievable 10,935 metres below sea level, which is 35,876 feet.
[6:56] SPEAKER_00: Wait, 35,000 feet?
[6:59] SPEAKER_00: Commercial airplanes fly at that height.
[7:02] SPEAKER_00: If you dropped Mount Everest into the trench, would it stick out?
[7:06] SPEAKER_01: Nope.
[7:07] SPEAKER_01: If you put Mount Everest at the bottom, there would still be over a mile of water covering the mountain's peak.
[7:13] SPEAKER_01: And down there in the dark, the pressure from all that water pushing down is absolutely crushing.
[7:20] SPEAKER_00: It's about 8 tonnes per square inch.
[7:23] SPEAKER_00: 8 tonnes on every single square inch?
[7:26] SPEAKER_00: What does that even feel like?
[7:28] SPEAKER_01: Imagine lying on the ground and having 50 jumbo jets stacked on top of your chest.
[7:34] SPEAKER_01: That pressure would flatten almost any human-made machine instantly.
[7:39] SPEAKER_00: So obviously, absolutely nothing can live down there.
[7:43] SPEAKER_00: It must just be empty rocks and mud.
[7:46] SPEAKER_01: That is exactly what scientists thought for decades.
[7:49] SPEAKER_01: But in August 2022, a research team led by Professor Alan Jameson sent special baited cameras deep into the oceanic trenches near Japan.
[8:00] SPEAKER_00: And what did they find?
[8:01] SPEAKER_00: A giant armoured sea monster with metal scales?
[8:05] SPEAKER_01: Even weirder! At a staggering depth of 8,336 metres, or 27,349 feet, they filmed the deepest fish ever recorded in history.
[8:19] SPEAKER_00: It's a species of Pseudoliparis snailfish.
[8:23] SPEAKER_00: Snailfish?
[8:25] SPEAKER_00: It sounds slimy and kind of gross.
[8:27] SPEAKER_00: Does it have thick armour to block the jumbojet pressure?
[8:31] SPEAKER_01: The exact opposite.
[8:32] SPEAKER_01: It looks like a pale, completely gooey, half-metre-long tadpole.
[8:38] SPEAKER_01: It has zero scales.
[8:40] SPEAKER_01: It turns out having a soft, squishy body is the secret to surviving, a pressure equivalent to the weight of 1,600 elephants.
[8:50] SPEAKER_00: 1,600 elephants of pressure?
[8:54] SPEAKER_00: And a squishy little fish just swims around in the pitch black like it's a normal Tuesday.
[9:00] SPEAKER_01: Yup, it is perfectly adapted to the extreme environment.
[9:04] SPEAKER_01: In fact, the Hedle snail fish even has gaps in its skull.
[9:08] SPEAKER_01: Wait, holes in its head?
[9:10] SPEAKER_01: Why?
[9:12] SPEAKER_01: So the insane pressure doesn't crush its skull flat.
[9:15] SPEAKER_01: The pressure equalises through the gaps.
[9:18] SPEAKER_01: It's an amazing evolutionary trick.
[9:21] SPEAKER_00: That is the weirdest, coolest, and slightly grossest survival trick ever.
[9:27] SPEAKER_00: But Mira, taking a step back, why does all this matter?
[9:31] SPEAKER_00: The ocean's salt, the crazy trenches, why do scientists care so much?
[9:37] SPEAKER_01: It matters more than you might think.
[9:39] SPEAKER_01: First, the ocean's salt is critical for our survival.
[9:43] SPEAKER_01: Without salt, the water's freezing point and density would completely change.
[9:48] SPEAKER_01: Salt makes ocean currents circulate all around the globe, acting like a giant planetary heater that regulates Earth's climate and weather.
[9:57] SPEAKER_00: Oh wow! So the salt dissolving from rocks millions of years ago literally controls the weather for us up on land today.
[10:05] SPEAKER_00: Exactly, it's all connected.
[10:08] SPEAKER_01: And exploring these insane ocean depths shows us how incredibly resilient life really is.
[10:14] SPEAKER_01: If a gooey snailfish can survive under 50 jumbo jets of pressure in freezing toxic conditions, it changes our understanding of biology.
[10:24] SPEAKER_00: I bet it makes scientists wonder where else life might be hiding.
[10:28] SPEAKER_00: Like on other planets or moons with deep icy oceans, in space.
[10:33] SPEAKER_01: You hit the nail on the head.
[10:35] SPEAKER_01: Also, here's one more crazy fun fact before our quiz.
[10:39] SPEAKER_01: Seawater doesn't just have sodium and chloride.
[10:43] SPEAKER_01: A single drop of ocean water actually contains around 80 distinct chemical elements dissolved in it.
[10:50] SPEAKER_00: That is wild! So when you accidentally swallow a mouthful of ocean water at the beach, you aren't just drinking salt, you're tasting a tiny little piece of almost every element on Earth.
[11:01] SPEAKER_01: Alright, Finn, we've covered massive salt mountains and gooe deep-sea fish.
[11:06] SPEAKER_01: Now it's time for the quiz.
[11:08] SPEAKER_01: Are you ready?
[11:09] SPEAKER_00: Okay, my brain is totally packed with facts.
[11:13] SPEAKER_00: I'm ready.
[11:14] SPEAKER_00: Bring it on.
[11:16] SPEAKER_00: First question.
[11:17] SPEAKER_01: If you took all the salt out of the ocean and spread it over the land, how thick would the layer be?
[11:27] SPEAKER_01: Next one.
[11:29] SPEAKER_01: What were the names of the two brave explorers who squeezed into the tiny bathosphere in 1934?
[11:40] SPEAKER_01: Question three.
[11:42] SPEAKER_01: Exactly how deep is the Challenger Deep in the Mariana Trench, in either metres or feet?
[11:52] SPEAKER_01: Here's number four.
[11:54] SPEAKER_01: What kind of pale, gooey fish holds the record for being found the deepest in the ocean?
[12:05] SPEAKER_01: Last question.
[12:06] SPEAKER_01: What gas from the air makes rainwater slightly acidic so it can break down rocks?
[12:16] SPEAKER_01: Great job! Let's see how you did.
[12:19] SPEAKER_01: The first answer is the salt would be 500 feet thick, or about as tall as a 40-story building.
[12:28] SPEAKER_01: For question 2, the explorers were the biologist William Beebe and the engineer Otis Barton.
[12:35] SPEAKER_01: Number 3.
[12:37] SPEAKER_01: The answer is the Challenger Deep plunges down to 10,935 metres, which is 35,876 feet deep.
[12:50] SPEAKER_01: Question 4.
[12:51] SPEAKER_01: The deepest fish ever recorded is the squishy pseudo liparous snailfish.
[12:57] SPEAKER_01: And the final answer is it's carbon dioxide.
[13:01] SPEAKER_01: That's what starts the whole salt making process.
[13:04] SPEAKER_00: I still can't get over that snail fish.
[13:07] SPEAKER_00: Imagine living your entire life in the freezing dark with the weight of 1600 elephants on your head.
[13:15] SPEAKER_01: I know, nature is absolutely incredible.
[13:18] SPEAKER_01: And just think, the ocean is so vast that there are probably hundreds of other weird creatures down there just waiting to be discovered.
[13:26] SPEAKER_00: Well, if you listeners loved exploring the deep sea as much as we did, we have a huge favour to ask.
[13:33] SPEAKER_00: Please leave us a five-star review.
[13:35] SPEAKER_01: Yes, and in your review, tell us if you'd rather ride in the tiny bathosphere or swim with a gooey snailfish.
[13:42] SPEAKER_01: Just scroll down on your podcast app and tap the five stars.
[13:46] SPEAKER_00: Oh, and don't forget to check out our site kidopoly.com.
[13:50] SPEAKER_00: We've got tons of fun learning games, cool activities, and more awesome science stuff to explore.
[13:56] SPEAKER_00: Absolutely.
[13:57] SPEAKER_00: Head over to kidopoly.com.
[13:59] SPEAKER_01: And hey, if you want a shout out on the show, like Warner, Nathan and Halley, or just want to tell us what topic we should cover next, email us at hello at kidopoly.com.
[14:10] SPEAKER_01: We love hearing from you guys.
[14:12] SPEAKER_01: Thanks for exploring the deep with us today.
[14:14] SPEAKER_01: See you next time on Science Is Not Boring.
[14:17] SPEAKER_00: Bye everyone, keep exploring.

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