A teaching sequence from the Catastrophe unit Etna Activity 3 Rock A teaching sequence from the Catastrophe unit cracking science! version 1.0 Activity from the Catastrophe unit © upd8 wikid, built by cracking science 2009 This page may have been changed from the original 1 1

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. 2 2

Cat – Bought you some stones from Etna shop today Cat – Bought you some stones from Etna shop today. Smooth and shiny, just like you... Pedro x Engage 3 3

Any idea what they’re made from? Right. Check out Pedro’s stones. Beautiful, yes? discuss Elicit 4

The stones were formed from 100% Etna magma. Magma is that hot, liquid rock from under the surface. When it cools, it freezes into solid rock. Rocks from cooled down magma are called igneous rocks. Elicit 5

OK. Time to go back to Antonio. See you later! Explore 6

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. Explore 7

Any suggestions? Let’s work on lava barriers. What material shall we make them from? Best if it’s something we can find nearby. Any suggestions? discuss Explore 8

OK. We’ll look at rocks made from cooled down magma – igneous rocks. Test their properties and report back. Which is best for barriers? Explore 9 SS

Thanks. OK. Back to your training. Just one more thing. Like I said, we need a rock that’s available here on Etna. And that’s basalt. OK. Back to your training. Explore 10

Why so much basalt here on Etna Why so much basalt here on Etna? Why not granite, or another igneous rock? They’re all made from cooled down magma… …Let’s investigate. Explore 11 SS3

What did you find out? How does the cooling speed affect crystal size? discuss Explore 12

Right. The quicker salol cools, the smaller the crystals. But why? And what’s this got to do with igneous rocks? Explain 13

The same happens to magma. If salol cools slowly, the particles have longer to arrange themselves in a pattern. Big crystals form. The same happens to magma. Explain 14

The same happens to magma when it cools quickly. Quick cooling makes small crystals – the particles have less time to make a pattern. The same happens to magma when it cools quickly. Explain 15

Can you figure out why magma sometimes cools slowly, and sometimes fast? discuss Elaborate 16

discuss Elaborate 17

Some magma cools under the Earth’s surface. magma cooling slowly area where cooled magma has formed rock The surrounding rocks insulate the magma. So it takes a long time to cool down. Elaborate 18

The crystals have time to grow big. Granite is an example of a rock that was formed under the surface. Elaborate 19

When magma leaves a volcano, we call it lava. Lava cools quickly in cool air or under water. Elaborate 20

Rocks from quickly cooled lava have small crystals, just like Etna’s basalt. Elaborate 21

Any idea what might make lava cool very quickly? Sometimes the lava cools so quickly that crystals don’t have time to form at all. That explains bubbly pumice and glassy obsidian. Any idea what might make lava cool very quickly? discuss Elaborate 22

One last thing… Now you know all about igneous rocks… Let’s take another look at Pedro’s stones. Evaluate 23

So they are a type of rock called… 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… Evaluate 24

Cat – Just saw Letizia and Antonio looking v. worried Cat – Just saw Letizia and Antonio looking v. worried. Do they know something we don’t? Ped xxx Evaluate 25 25

Picture credits 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