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Hello, my name is Nidge.
And today on Imagine This, we're playing Scissors, Paper, Rock.
Scissors, Paper, Rock.
Woohoo!
Scissors, I win.
No, that's not true.
Scissors loses against rock.
Really?
Yeah.
Scissors are so sharp though, and they're made of metal.
That feels tougher than rock.
Because it smashes scissors.
Because they're harder than scissors or paper.
But I think rocks can break real scissors.
Yeah, rocks are so strong.
Austin and Monty have been wondering about rocks too.
I am Monty and I am six years old and I want to know how are rocks made?
Hi, my name's Austin.
I'm six years old and I would like to know what are rocks made out of?
Hmm, what do you reckon?
I think they're made with, like, some really hard powder that's been grinded up by a volcano.
Lava?
Magma?
Gas or something?
And then people come along and take the rocks away and spread them on the land.
You know who we should talk to?
Associate Professor Heather Hanley.
She's a geologist.
Geology is the science of rocks.
This place is hot.
Where are we?
Fire, rocks, lava.
We're at a volcano.
Oh, there's Heather.
Hi, Dr. Handley.
Hi.
Hello.
Oh, hi there.
What are you doing?
I'm a volcanologist, the type of geologist that studies volcanoes.
So what is a rock?
A rock is a solid piece of the earth.
You can have tiny pebbles, big stones, huge boulders.
The whole planet is pretty much a big rock.
Like when I go outside, I have lots of these little pebbles in front of my house.
In my garden, outside in the bush, the city, the waterways.
How do they all get made?
Yeah, we want to know how rocks are made.
Well, there are three main types of rock.
Igneous, sedimentary... and metamorphic.
Rocks from volcanoes are igneous rocks.
They form when this liquid lava cools down and turns solid.
The lava cools down which makes it really hard, which makes the rock a rock.
And there are even more igneous rocks under the ground too.
Want to go see?
Yeah!
We'll have to use our imaginations.
You're talking to the right people.
We're practically imagination athletes at this point.
Alright, we'll step inside my subterranean submarine.
I call her Velma.
Hi Velma!
She's equipped with anti-melty shields, drills to get through bedrock and the best air conditioner in the universe.
All aboard, here we go.
Oh, it's so bright.
The lava's like gloopy red hot soup.
I see lava around me and rocks burning red colour.
Lava is called magma down here.
It's the same stuff.
We just call it lava when it pours out of the volcano onto the ground, and we call it magma when it's under the ground.
So magma is all just melted rocks under the ground?
Yeah, we call it molten rock.
It's full of different elements like iron and calcium.
Hmm, sounds nutritious.
You can't eat it, Nidge.
How does it turn into hard rocks?
When it's too hot, nothing can stick together.
But as the magma cools down, the elements start joining together and they start to make... Crystals!
I love crystals.
Aren't they lovely?
They come in the rainbow colours.
I think they're like rocks that have shiny glitter paint on them.
Yeah.
Maybe they're made of the same material as rocks?
Yes.
Most rocks are made from crystals.
We call them minerals in geology.
They are the building blocks of rocks.
You know how sometimes you can see little sparkly flecks in rocks?
Those are tiny crystals.
If the magma cools down over a really long time, bigger crystals can grow and then the rocks can look more speckled and multicolored.
So is igneous rock only found near volcanoes?
No, you can find igneous rocks in lots of places.
And that's because Earth used to be almost entirely molten.
Like when dinosaurs were alive?
Way before then.
While we're down here, can we see the other types of rocks being made too?
We could hang around here for a few million years waiting for them to form.
But it might get a little boring.
That would take a long time.
And I didn't pack any snacks.
Yeah, come on.
Let's catch this magma flare out of here.
Out of the volcano?
How else?
Yeah!
Get ready for eruption in three, two, one.
Whoa!
Whew!
We're back on solid ground You mean solid rock?
Oh yeah, We're on a mountain.
There are lots of rocks here, Big ones, small ones.
Check out this big boulder here.
This is granite, A type of igneous rock that forms underground over a long time.
So how did it get here?
Rocks don't have legs.
But they can move around.
The movements of the earth can lift them up.
Is it an earthquake?
Quick, get back in Velma.
When things move around, rocks can break off from mountains.
The boulder's rolling down the hill.
Let's follow it.
Whoa, the boulder's breaking up into smaller rocks.
And they're going in the river.
Rocks on the surface of the earth tend to break down.
Plants can split them up with their roots, or they can break apart if ice gets into their cracks.
It's called weathering.
Even the rain can break them down.
Really?
You wouldn't notice it.
It takes such a long time.
But yes, Rainwater can dissolve rocks.
And so can a rushing river like this one.
That igneous rock that was once part of a huge mountain broke off to become a big granite boulder and now it's broken up even more to become a small pebble heading downstream.
You're looking seasick!
It's like being in a washing machine.
And it will go for a long time and then turns really, really small.
Yes.
Rocks can get knocked against other rocks, dragged against the riverbed, and water pushes against them and changes their shape.
This is called erosion.
And then it's smoother because all the other rocks hit all the jagged parts away.
We're seeing this in bath time.
It would take many years for a big jagged rock to become a smooth river pebble, but it shows you how powerful water is.
Then it should be scissors, paper, rock, water Not too complicated Where's this little pebble going?
Where most rivers end up, the ocean We're at the beach.
Yeah, woohoo, I love the beach.
But hang on, there's no rocks here.
I'd like to see sand.
Where's our smooth pebble gone?
The rock turned into sand.
What?
How?
As that little rock got smoother, it also got smaller, because little tiny specks of it were coming off in the water.
Ah, it eroded.
Try and control until it turns into sand.
But rocks are brown and grey and even black.
This sand is golden.
That's because the darker minerals, the stuff that's inside rocks, were broken down and dissolved in the water.
What's left is a mineral called quartz, and it's really tough.
It lasts longer than most other minerals and it gives sand that golden colour.
Over many, many years, this sand will get carried out to sea and it will get buried by more and more sand and pushed down beneath the weight of the ocean until it starts to change.
If we travel down under the ocean, under the sea floor, you start to see layers of different sand lying flat on top of each other.
It looks like a stack of pancakes.
Now I want some pancakes.
It's not sand anymore. turned hard like rock.
Yep, it's sedimentary rock.
Rocks and coral and shells and all kinds of things can be worn down into a fine sand.
We call it sediment.
Layers and layers of this sediment are buried for millions of years until they turn into hard rock.
Whoa, was that a dinosaur fossil?
Yeah, you'll find those here in sedimentary rock.
Oh, cool.
So sedimentary rock is made from layers of sediment like sand, All smooshed together really, really tight.
Yep.
What about the third type?
Meta... Metamorphius?
We're going to have to go even deeper underground for that part.
Oof, Velma, can you put the air conditioning on please?
It's getting hot down here.
Yes, the deeper underground you go, the warmer it gets and the more the pressure builds, because the weight of everything sitting on top of it just gets heavier and heavier.
Hey Heather, something weird is happening.
The rocks are changing.
Yes, they're becoming metamorphic.
Metamorphic.
Metamorphic means things have experienced some kind of transformation.
And these rocks are transforming under such extreme pressure and heat.
They're still rocks. but the minerals inside them are becoming different minerals now.
It looks like the rocks are melting.
Yep, those straight lines in the layers of sedimentary rock start to get all wiggly and wonky.
It's getting really hot again.
It's turning into magma.
Sedimentary and metamorphic rocks can get pushed so deep underground they start to melt.
Can you hear that?
The pressure can build up so much that the magma, the molten rock, finds a way out towards the surface.
And erupts as lava from a volcano.
We're back at the volcano.
What?
Right back to igneous rock forming from cooling lava.
Wow.
It's like a full circle.
It's like a life cycle for rock.
That's right.
It's called the rock cycle.
It's the way parts of the Earth, our big planet of rock, break off and wear away and get turned back into rock in an endless cycle.
It doesn't always happen in that order.
It depends on where the rock is and what pressure it's put under.
Igneous rock can become metamorphic and skip sedimentary.
And igneous rock can melt and harden back into more igneous rock.
The rock cycle rocks!
Hey, we should start a rock band.
We could be called the Rockettes.
Or Rockabye Baby.
Rock and roll!
So, Austin and Monty, the Earth is kind of like one big rock formed billions of years ago.
As hot molten magma cooled down, the earth turned hard and it made different kinds of rock pieces of earth break off and join back together in a never-ending cycle, the rock cycle.
Mountains form and then slowly wear away with rain and wind, and over millions of years Those big mountains might become dry deserts or the sand at the beach.
Layers of sand can be buried and pressed together so tightly they harden back into rock or get pushed down into the earth so deep they can melt back into magma.
The next rock you come across probably had a long life.
It might have sat untouched on the land for thousands of years or waded underwater in the deepest of oceans.
Or even seen a dinosaur!
Yeah!
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