Why Isn’t The Earth All Ocean? | Between Two Nerds #2 | Science Podcast

Why is it that the ocean isn’t just ocean? It’s land and ocean. That’s another great question. It wasn’t always the case; there was a time
when our Earth was just land. Do you remember it? I didn’t even know that. It’s a very long time ago, maybe Eugene might
remember it. Pre-Eugene. Pre-Eugene, so a very long time ago. So when the earth was first made, it was really
hot and all pretty much lava. A big ball of lava in space. And there just was no water yet, and the lava
cooled, and we got land, right? And still no ocean yet. And water, so the water for our oceans right,
we think actually we’re not quite sure where it came from. We actually think it might have come to us
from space. Cool. Does water rain down from space? Clouds, not space. Yes, exactly clouds. So there are these big giant ice cubes floating
around in space, that’s weird right. We don’t call them ice cubes; we call them
comets. Have you heard of a comet? Yes. So you have asteroids which are mostly rock,
and then you have comets which are a mixture of rock and a lot of ice. So scientists think that actually, these comets
hit our earth at the start when it was just made and that ice, what would happen to the
ice when it hit the Earth? It melts. And that melted comet ice water turned into
our oceans. The Earth is not perfectly smooth, so you
get hills, have you ever seen a hill? Yes. Good. You ever seen where the earth goes low in
a valley? Well, let’s take a bath; have you ever seen
a bath? Yes. So imagine the bath is planet earth, and we’re
going to fill that bath with water. Now at the point where you’re going to get
in the bath, there are bits in the bath that are still above the water around the sides. So that’s like our land, and then there are
other bits of the bath that are underwater, and that’s like the bottom of the ocean. So the bits of land that are high enough are
land and the bits that aren’t high enough get covered in the water. So the ocean isn’t one depth, do you know
the deepest place in our ocean? Yes. Do you, what is it? Mariana Trench. Oh my goodness, well done. So that is super deep, it’s like 11 kilometres,
or so you know the Burj Khalifa, don’t you? Yes. So you can fit about 15, let’s say, that might
be wrong. Let’s say 14-15 Burj Khalifa’s end-on-end
underwater before you got to the bottom, so that’s crazy deep. Now, if you go out there and just step into
the ocean, it might be that deep. But as you walk up the hill, you’ll come out
of the ocean, and you’ll be on the beach. So all the higher bits of land are the bits
that we live on, and all the lower bits are the bits that get covered. So that’s why you get some land thankfully,
and some ocean. If all the land was lower, where would we
live? But you’ll be alright because you’re a clownfish. If the ice in Antarctica and the North Pole
in the Arctic melt, now do you think we’ll have more water on our planet? More or less, if all the ice in on planet
Earth melts? More. Okay. So now we have more water, now do you think
the lowest bits like around the beaches. Do you think you’ll still have the beach where
we do now? Yes. But would it be above the water or below the
water? Above. It’ll actually be below because now we have
more water, so the seas will rise, and all these lower bits will be underwater and disappear
under the sea, which won’t be great. And then we’d have to move to higher ground
— actually some countries, some parts of the world that are actually very low land. So you know the Netherlands in Europe, Holland? Yes. So that’s actually a very low country. So to get the land, they had to push all the
water out and build walls to keep the water away, just to have the land where they live
on right now. But if now the waters rise… Doesn’t sound safe. Yes. So this could change, the amount of land you
see out on the globe right now would change if the water levels change. Make sense? Yes.

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