Rocks make up the earths crust
Igneous rocks:
- formed when magma/lava solidifies
- made of interlocking crystals- makes them hard and resistant to erosion
- have small crystals if liquid rocks cools quickly (e.g. basalt)
- have large crystals if liquid rock cooled slowly (e.g. granite)
Sedimentary rocks:
- formed when layers of sediment are compacted over a long period of time
- erode more easily than igneous and metamorphic rocks
- made of rounded grains and may contain fossils
- include chalk and limestone (natural forms of calcium carbonate)
Metamorphic rocks:
formed from existing rocks by action of heat and/or pressure, causing new interlocking crystals. E.g. marble which is formed from chalk or limestone.
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