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Rock Types
There are three main types of rocks: igneous, sedimentary, and metamorphic. Igneous rocks form when magma cools and crystallizes, either underground or on the surface. Sedimentary rocks form through the compaction and cementation of sediments, usually deposited by water. Metamorphic rocks were originally igneous or sedimentary rocks, but were changed by extreme heat and pressure within the Earth's crust, altering their structure. Rocks can be transformed between these types through the rock cycle as they are weathered, eroded, deposited, buried deep within the Earth, and sometimes melted.
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Rock Types
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- 2. Types of rocks The3 types are: Igneous Sedimentary Metamorphic
- 4. Igneous rocks Igneousrocks are formed from molten rock called magma. They are mostly crystalline (made up of interlocking crystals) and usually very hard to break. E.g. granite, basalt, andesite. Basalt
- 5. The formation ofigneous rocks magma volcano Extrusive igneous rocks are cooled quickly so small crystals form (e.g. basalt). Intrusive igneous rocks are cooled more slowly so large crystals form (e.g. granite).
- 6. Basalt pillars These pillarswere formed when lava cooled on the Earth’s surface.
- 7. Sedimentary Sedimentary rocksare formed from sediment grains deposited by water, wind or ice. They are always formed in layers, called “beds” or “strata”, and quite often contain fossils. E.g… Sandstone Limestone Chalk
- 8. The formation ofsedimentary rocks These were formed from layers of sediment which were squeezed together. new deposits layers of sediments getting older sea/lake/river land rivers
- 9. Metamorphic Metamorphic rockswere once igneous or sedimentary rocks, but have been changed (metamorphosed) as a result of intense heat and/or pressure within the Earth’s crust. E.g… Slate Marble Gneiss, pronounced
- 10. Metamorphic rocks areformed by the effect of extreme pressures and temperatures deep within the Earth. This alters the structure of the existing rock. Metamorphic rock - formation
- 11. The formation ofmetamorphic rocks magma sedimentary rocks are changed here due to heat and pressure. volcano
- 12. Continent collision causesmetamorphism and huge folds like this one in Scotland. Metamorphic rocks
- 13. Rock type DefinitionFormation Example Igneous Rocks formed of interlocking crystals. Tough, hard and resistant to erosion Formed by the cooling of molten magma either underground (intrusive) or on the ground (extrusive) due to volcanoes Basalt, granite Sedimentary Formed in layers called strata. Often contain fossils. Some are tough and others are weaker than igneous or metamorphic rocks Formed by the compaction of sediments, usually deposited by the sea. Sandstone, limestone, shale, clay Metamorphic Also formed of interlocking crystals. Very tough and resistant to erosion Formed by heat and/or pressure changing existing sedimentary or igneous rocks to metamorphic rocks Slate, marble
- 14. sea volcano rocks are broken upby the action of weather magma slow solidification high pressure and temperature transportation and deposition rises to surface where it cools rapidly melt rocks rise to surface by uplift and erosion Igneous rocks basalt Igneous rocks granites magma Metamorphic rocks slate and marble Sedimentary rocks mudstone
- 15. sea volcano Igneous rocks basalt Igneous rocks granites rocksrise to surface by uplift and erosion rocks are broken up by the action of weather magma Metamorphic rocks slate and marble Sedimentary rocks mudstone slow solidification high pressure and temperature transportation and deposition rises to surface where it cools rapidly melt
- 16. Homework: Task – imagineyou are a rock, describe your journey through the rock cycle. Things to include: Are you an igneous, metamorphic or sedimentary rock? What type of rock are you e.g. granite, limestone.