Igneous rock
I can explain how igneous rocks form and describe features of different types.
- Year 8
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.
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.
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.
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
Lesson video
Loading...
Prior knowledge starter quiz
6 Questions
Q1.What are the key components that make up rocks?
Q2.Match the following rock types with their descriptions.
Q3.A mineral is a substance with a crystal structure, while a rock consists of one or more minerals or rock fragments.
Q4.Which of the following is evidence that supports the idea of tectonic plates moving?
Q5. rocks have spaces between grains, allowing water to pass through.
Q6.Which of the following features is commonly found in igneous rocks?
Assessment exit quiz
6 Questions
Q1.Which of the following is the correct name for molten rock that has broken through Earth's crust?
Q2.Which of the following is a type of igneous rock that forms inside Earth's crust?
Q3.Which of the following factors determines the size of crystals in igneous rocks?
Q4.Sort the following steps into the correct order to describe how the melting of rock at the edge of a tectonic plate leads to the formation of extrusive igneous rock (e.g. basalt).
Q5.Which of the following is an example of an intrusive igneous rock?
