1. Types of Rocks

2. Types of Rocks There are three main types of rocks:
Igneous - formed when molten rock cools.
Sedimentary – formed by the “cementing together” of small grains of sediment.
Metamorphic – rocks changed by the effect of heat and pressure.

3. Igneous Rocks
These are rocks formed by the cooling of molten rock (magma.)
magma
volcano
Magma cools and solidifies forming igneous rocks

4. **The faster the magma cools, the smaller the crystals will be**
Igneous Rocks
Intrusive Igneous Rocks
Cool INSIDE the earth
Have LARGE crystals
Extrusive Igneous Rocks
Cool OUTSIDE the earth
Have SMALL crystals
**The faster the magma cools, the smaller the crystals will be**

5. Igneous Rocks
This piece of obsidian cooled so FAST on the SURFACE that it did not have time to form any crystals.

6. Igneous Rocks
This piece of rhyolite also cooled on the SURFACE very FAST and has small crystals.

7. Igneous Rocks
This piece of granite cooled slowly INSIDE the Earth and has LARGE crystals.

8. Sedimentary Rocks
Sedimentary Rocks are rocks formed when particles of sediment build up and are “cemented together” by the effect of pressure and minerals.
Getting older
sea
Fragments washed to the sea
Sedimentary
rocks
Rocks are broken
up by the action
of weathering

9. Sedimentary Rocks Have grains, which are the bits of sediments
Grains can be big or small
Sometimes rub off on your hands

10. Sedimentary Rocks
The only rocks with FOSSILS

11. Sedimentary Rocks
Sometimes layers are visible

12. Metamorphic Rocks
Metamorphic rocks are formed by the effect of heat and pressure on existing rocks.
This can greatly affect the hardness, texture or layer patterns of the rocks.
Magma
Pressure from surface rocks
metamorphic
rock
forming
here
heat

13. Metamorphic Rocks
There is a change in foliation (how the minerals line up)

14. Metamorphic Rocks
Banded light and dark colors

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