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EtnaActivity 3 Rock

A teaching sequence from the Catastrophe unit

cracking science!

Activity from the Catastrophe unit © upd8 wikid, built by cracking science 2009 This page may have been changed from the original

2

To learn how igneous rocks are formed.

To work out which is the best type of igneous rock for a lava barrier.

To discover reasons for igneous rocks’ different properties.

Cat – Bought you some stones from Etna shop today. Smooth and shiny, just like you... Pedro x

3Engage

Any idea what they’re made from?

Right. Check out Pedro’s stones. Beautiful, yes?

4Elicitdiscuss

The stones were formed from 100% Etna magma.

5Elicit

Rocks from cooled down magma are called igneous rocks.

Magma is that hot, liquid rock from under the surface. When it cools, it freezes into solid rock.

OK. Time to go back to Antonio.

See you later!

6Explore

Predicting lava flow is all very well.

But what if the lava is approaching a town?

We need to stop it, or divert the flow.

7Explore

Let’s work on lava barriers.

What material shall we make them from? Best if it’s something we can find nearby.

8Explorediscuss

Any suggestions?

OK. We’ll look at rocks made from cooled down magma – igneous rocks.

9Explore SS

Test their properties and report back. Which is best for barriers?

Just one more thing.

Like I said, we need a rock that’s available here on Etna. And that’s basalt.

10Explore

OK. Back to your training.

Thanks.

Why so much basalt here on Etna? Why not granite, or another igneous rock?

11Explore SS3

…Let’s investigate.

They’re all made from cooled down magma…

What did you find out?

12Explorediscuss

How does the cooling speed affect crystal size?

Right. The quicker salol cools, the smaller the crystals.

13Explain

But why? And what’s this got to do with igneous rocks?

If salol cools slowly, the particles have longer to arrange themselves in a pattern. Big crystals form.

The same happens to magma.

14Explain

Quick cooling makes small crystals – the particles have less time to make a pattern.

The same happens to magma when it cools quickly.

15Explain

Can you figure out why magma sometimes cools slowly, and sometimes fast?

16Elaboratediscuss

17Elaboratediscuss

magma cooling slowly

area where cooled magma has formed rock

18Elaborate

The surrounding rocks insulate the magma. So it takes a long time to cool down.

Some magma cools under the Earth’s surface.

Granite is an example of a rock that was formed under the surface.

19Elaborate

The crystals have time to grow big.

When magma leaves a volcano, we call it lava.

Lava cools quickly in cool air or under water.

20Elaborate

Rocks from quickly cooled lava have small crystals, just like Etna’s basalt.

21Elaborate

Sometimes the lava cools so quickly that crystals don’t have time to form at all.

That explains bubbly pumice and glassy obsidian.

22Elaboratediscuss

Any idea what might make lava cool very quickly?

23Evaluate

One last thing…

Now you know all about igneous rocks…

Let’s take another look at Pedro’s stones.

24Evaluate

They are made from…

So they are a type of rock called…

They contain small crystals. This shows that…

I think the name of the rock is…

Cat – Just saw Letizia

and Antonio looking v.

worried. Do they know

something we don’t?

Ped xxx

25Evaluate

Picture Slide Credit

Basalt Breccia 9 commons.wikimedia.org

Salol crystals after slow cooling 14 SPL – Martyn F. Chillmaid

Salol crystals after fast cooling 15 SPL – Martyn F. Chillmaid

Igneous structures 17 commons.wikimedia.org

Pahoehoe toe 20 commons.wikimedia.org

Hand sample of Basalt 21 SPL – Mark A. Schneider

Picture credits

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