Igneous rock
I can explain how igneous rocks form and describe features of different types.
Igneous rock
I can explain how igneous rocks form and describe features of different types.
Lesson details
Key learning points
- The melting point of rock is very high.
- Melted rock is called either lava (on Earth's surface), or magma (underground).
- Extrusive igneous rock forms outside Earth's crust, while instrusive igneous rock forms inside the crust.
- Some substances form crystals when they freeze.
- Crystal size depends on the rate at which melted rock cools.
Common misconception
Some think all lavas/magmas are the same and the type of igneous rock formed depends on cooling rate.
Stress that the type of igneous rock formed depends upon the mineral composition of the lava/magma *and* the rate of cooling. Use examples to reinforce this.
Keywords
Lava - Molten (i.e. melted) rock that has broken through Earth's crust.
Magma - Molten (i.e. melted) rock beneath the Earth's surface.
Crystallisation - A process in which solid crystals form as molten rock cools.
Extrusive - A type of igneous rock that form when lava has cooled and crystallised; they form above Earth's surface.
Intrusive - A type of igneous rock that form when magma has cooled and crystallised; they form under Earth's surface.
Equipment
Per group: melted salol, dropping pipette, 2 × cold microscope slides (kept in freezer), 2 × warm slides (kept in 45°C water bath/oven prior to use), hand lenses, optional extra – A5 black card.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Video
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Starter quiz
6 Questions
contain crystals that point in many directions
contain grains that are stuck together and may contain fossils
contain large crystals that all line up
Exit quiz
6 Questions
