The Rock Cycle – Types
Magma
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Rocks are created from magma (below ground) and lava (above ground)
There are 4 forces, which affect rocks:
1. Cooling
2. Weathering and Erosion
3. Heat and Pressure
4. Heat causing melting
Igneous Rock
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Formed when magma (or lava) is cooled
Cooling can occur underground, above ground, or under water
Characteristics: crystal structures and metallic minerals
o e.g. granite
Intrusive – granite occurs below the surface
Extrusive – cooling occurs near the surface; minerals such as basal, gold, silver
Igneous rock may be subjected to heat, heat and pressure, or weathering and
erosion
Sedimentary Rock
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When rock experiences weathering and erosion, it is broken down eventually
into fine particles called sediment
Through compaction and cementation these sediments form sedimentary rock
Characteristics: fine particles, layering of particles, and fossils of sea animals
o e.g. sandstone
Fossil fuels are associated with this type of rock (e.g coal, oil, natural gas, salt,
and potash)
Sedimentary rock will also experience heat, heat and pressure, or weathering
and erosion
Metamorphic Rock
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When rocks are exposed to heat and pressure their structure will transform into
metamorphic rock – “changed” rock
o e.g. marble
Metamorphic rock will also experience heat, heat and pressure, or weathering
and erosion to form other types of rock
Metamorphic, igneous, and sedimentary rocks can sometimes melt and form
magma