Rock Types

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  • 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


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