Unit 1A - Types of Rock

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  • Types of Rock
    • Igneous Rocks
      • Intrusive
        • These form when magma cools down below the Earth's surface
          • The magma cools down very slowly, forming large crystals that give the rocks it's coarse texture
            • Large domes of cooled magma are called batholiths
            • When magma has flowed into gaps in the surrounding rock it forms
              • Dykes in vertical gaps
              • Sills in horizontal gaps
        • Example:Granite
      • Extrusive
        • These form when magma cools down after it's erupted from a volcano onto the earths surface
          • Them magma cools down very quickly, forming small crystals that give the rock it's fine texture
        • Example:Basalt
    • Sedimentary Rocks
      • Sedimentary rocks are formed when layers of sediment are compacted together until they become solid rock
        • This is called lithification
    • Metamorphic Rocks
      • Metamorphic rocks are formed when other rocks such as igneous, sedimentary and older metamorphic are changed by heat and pressure


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