Igneous - Hardened up magma from inside the Earth, or hardened up lava from volcanoes
Sedimentary - Layers of sediment compacted and cemented together
Metamorphic - Other types of rock changed by extreme heat and/or pressure

Porous Rocks - Liquid can pass through
Non-porous rocks - Liquid cannot pass through

How are Sedimentary rocks formed?

1. Sedimentation
Bits of rock are broken off, transferred by the river to the river bed.
2. Compaction
The weight of the layer on top squeezes out water and squashes the sediment together.
3. Cementation
Salt crystals "glue" cement pieces or sediment together.

How are Igneous rocks formed?

If the magma cools quickly -> Small crystals form in the rock
If the magma cools slowly -> Large crystals form in the rock
No fossils form because the magma/lava melts it

Weathering
3 types
-Physical weathering
-Chemical weathering
-Biological weathering

Physical weathering:

When it is extremely hot -> Rock expands
When it is extremely cold -> Rock contracts

Wind, Rain and Wave

Wind blows tiny grains of rock away
Rain and waves -> liquid gets into small cracks

Freeze - Thaw
-Water inside rock freezes
-This forces the rock open and makes a big crack in the rock
-When the ice thaws, water seeps further down the rock
-Repeat

	Created by mate spark over 8 years ago

Rocks and how they are formed