Rock Types
- Created by: Qiao-Chu
- Created on: 13-04-13 17:18
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- Rock Types
- Introduction
- Earth's crust is thin outer layer of earth, surrounds mantle and core
- Igneous, sedimentary and metamorphic rocks make up the earth's crust
- Igneous
- Formed by cooling molten magma either underground (intrusive) or overground (extrusive)
- Linked to volcanic activity
- Composed of interlocking crystals (crystalline), tough rocks and resistant to erosion
- Extrusive - basalt, andesite, rhyolite. Intrusive - granite, gabbro, dolerite
- Sedimentary
- Formed by compaction and cementation of sediments, usually deposited in sea
- Also includes organic material such as coal and rocks precipitated from solutions like limestone
- Usually form layers called beds, contain fossils
- Some rocks tough such as limestone, most are weaker than igneous and metamorphic
- Sandstone, limestone, shale, clay and mudstone, chalk is a form of limestone
- Metamorphic
- Formed by alteration of pre-existing igneous, sedimentary or metamorphic rocks by heat or pressure
- Also crystalline, exhibit layering called cleavage and banding
- Tough and resistant to erosion
- Slate, gneiss, schist
- Introduction
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