[♪ INTRO]
Wow, Squeaks, that’s incredible!
Squeaks and I are learning about Antarctica,
and this says that the biggest glacier in the world is there.
We’ve talked about glaciers here at SciShow Kids before,
so you might remember a bit about them.
[Squeaks defines “glacier”]
Exactly!
Glaciers are kind of like giant ice cubes on Earth.
You can find them in places where it’s so cold,
the snow doesn’t fully melt away in the spring.
They form when a lot of snow falls in the same place every year,
and gets packed down over a long time — sometimes, more than 100 years.
Eventually, the packed snow freezes into ice,
getting thicker and thicker, until you have a giant piece of it.
And the ice gets so heavy that it starts to move,
slowly sliding across the ground.
We call this giant, moving ice a glacier.
Nowadays, you can only find glaciers in a few places —
usually high up in mountains or in super cold places like Antarctica.
But long ago, a lot of Earth used to be covered in glaciers.
[Squeaks squeaks]
That’s a really good question.
Squeaks asked how we know the Earth used to be covered in glaciers,
when most of them aren’t here anymore.
Well, those glaciers left clues behind,
and we can still see those clues today!
When glaciers move, they change the land that they move over.
Glaciers can pick up dirt, sand, and even big rocks,
and push and scrape them against the Earth.
And when the glacier is gone, those signs are still there.
Here, I have a good way to show this.
Let’s make a model!
You can use models to make the world easier to understand —
especially if the thing you want to learn about is too big,
far away, or rare to study in person.
In this case, glaciers move so slowly, it’s hard to see them in action.
But we can make a model of a glacier with this ice cube tray!
If you want to build your own glacier model, you’ll need an ice cube tray;
some small rocks, sand, or dirt; water; some modeling clay;
a freezer; and a grown-up helper.
Alright Squeaks, I’m going to pretend that our glaciers moved over
some sandy areas, and some rocky areas, and even a big hill made of dirt.
As it moved, it picked up bits of sand, rock, and dirt.
We call this stuff glacial till.
I’ll put a bit of glacial till in the bottom of our ice cube tray,
and then fill the tray up the rest of the way with water.
I’ll put this tray in the freezer, and wait for our mini-glaciers
to freeze up!
[Squeaks asks what to do next.]
Well, while we wait, let’s make the land for the mini-glaciers
to move over.
We’ll make a big flat surface by rolling out some modelling clay.
Let’s roll out a really big, flat rectangle.
Alright!
Let’s go check the icecube tray!
Okay, our rectangle is ready, and our mini-glaciers are frozen!
Next, we’ll put the side of the mini-glacier with the dirt and rocks
on the bottom, so they’re up against our modelling clay “Earth”.
Glaciers are really heavy, so when they move,
there’s a lot of pressure, or force, on the Earth —
in other words, they push down on the Earth pretty hard.
We can do the same thing here by pushing down on the mini-glacier
really hard as we slowly scrape it across the clay.
We’ll do this a few times…
...and we’re ready.
Let’s take a look and see what happened!
[Squeaks squeaks excitedly]
Whoa, the heavy pressure from our mini-glacier pressed
the glacial till against our land, and left huge scratches.
[Squeaks squeaks]
Yeah, this looks just like what happens in real life!
When glaciers leave scratch marks on big rocks or in the ground,
scientists call the marks glacial striations.
But that’s not all glaciers can do: Sometimes, instead of scratches,
glaciers can carve out a big chunk of land, leaving a big hole behind.
Rain can fill up the hole with water over time,
and some of the glacier may even melt there.
What do you think places where that happened might look like today, Squeaks?
[Squeaks squeaks]
That’s right!
Some of these big holes that glaciers make in the Earth become lakes!
They can be really big lakes, too, like the Great Lakes
here in North America.
Those giant lakes were carved out of the Earth by giant glaciers
more than 10,000 years ago.
[Squeaks squeaks]
Oh, what happened to the dirt that was dug up?
Well, a few things can happen.
For one thing, not all of the bits of sand, rock, and dirt carved out
of the Earth by glaciers get stuck to the glacier forever.
Sometimes, if the glacier sits in the same spot for a while,
pieces of it will melt, and that sand and dirt we call
glacial till will fall to the ground.
When this happens, it can leave big piles of sand and dirt!
These big piles are called moraines, and eventually,
they become a permanent part of the land.
Trees and plants even grow on them!
There are moraines all over, and they show us exactly
where glaciers sat.
A big part of the Cape Cod area in Massachusetts is actually part of
a big glacial moraine, where people now live on old glacial till!
In our model, we changed the land very quickly, but in real life,
the changes happen very slowly, over hundreds or even thousands of years.
Glaciers long ago left so many clues all over the world.
Look around, and maybe you’ll find some clues where you live!
Maybe you can even find a lake made by a glacier.
Explore your neighborhood, or even try your own
mini-glacier experiment at home!
And if you’d like to keep discovering new things with Squeaks, me,
and all of our friends, make sure to hit subscribe.
We’ll see you next time, here at The Fort.
[♪ OUTRO]