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  • 1. Types of Rocks
  • 2. Igneous Rock
    • rock: a material made up of one or more minerals
      • rocks are not crystals - minerals are crystals
      • some rocks form at or near Earth’s surface
      • some rocks form deep in the crust - in the Earth’s middle layer (mantle)
    • rocks are classified into 3 groups based on how they are formed
  • 3.
    • igneous rock: rocks that forms when melted rock hardens
      • lava is melted rock that reaches Earth’s surface
      • lava cools and hardens quickly
        • large mineral pieces do not have time to form
        • rocks formed from lava have small mineral pieces and are called fine-grained
  • 4.
    • magma: melted rock below Earth’s surface
      • magma cools and hardens slowly
      • minerals can form large grains that are easy to see
      • rocks formed from magma are called coarse-grained
  • 5.
    • basalt is the most common igneous rock
      • forms from lava at Earth’s surface
      • dark, greenish-black rock
      • made of minerals feldspar and pyroxene
    • gabbro is an igneous rock made of feldspar and pyroxene
      • has larger mineral grains
      • forms inside Earth instead of at surface
    basalt gabbro
  • 6.
    • pumice : another igneous rock
      • tiny holes in pumice caused from gases escaping from lava as it cools
      • feels rough and scratchy
    • obsidian : forms from lava
      • lava cools so quickly that rocks look like black glass
      • when it breaks sharp edges form
    • granite : common igneous rock
      • forms when magma cools slowly beneath Earth’s surface
      • made of large grains of feldspar, quartz, and mica
  • 8. Sedimentary Rock
    • weathering: how rocks are broken down into smaller pieces
      • wind, water, ice, and plant roots cause weathering
    • rocks weathered into small pieces and moved to other places by wind, water, gravity, or slow moving glaciers
      • erosion: movement of weathered rock pieces from one place to another
  • 9.
    • erosion caused by water - over time rock pieces drop to lake, river, stream bottoms
      • this material is sediment
    • layers of sediment form sedimentary rock because all the layers squeezed and get stuck together
    • conglomerate is a type of sedimentary rock
      • pieces can be big as boulders or small as peas
      • pieces are round and smooth
      • form in shallow water
  • 10.
    • smaller sediments are carried farther and dropped later
      • siltstone is a rock made of smaller sediments
    • limestone : fine-grained sedimentary rock
      • made of mostly mineral calcite
      • forms in oceans
        • sometimes from seashells
      • a few form in lakes
  • 11.
    • sandstone another kind of sedimentary rock
      • made of bits of rock and minerals the size of sand grains
      • nearly all sandstone is made of mostly the mineral quartz
      • some sandstone are fine-grained
        • feel smooth when you touch them
      • some sandstone are coarse-grained
        • feel rough against skin
      • can form on land or in water
  • 12.
    • shale : fine-grained sedimentary rock
      • made of small sediments
      • sediments so small that you can only see them with a magnifying glass or microscope
  • 13. Metamorphic Rocks
    • metamorphic rocks: rocks that were changed due to high heat and pressure
      • texture (the way a rock looks and feels) and the minerals that make up the rocks are changed
    • metamorphic rocks can form from any rock
      • sedimentary, igneous, or other metamorphic rocks
  • 14.
    • some metamorphic rocks form when mountains built up
      • schist
        • has wavy lines
        • splits into layers easily
      • gneiss
        • forms when schist is heated and squeezed more
        • has bands of light and dark minerals
    Schist Gneiss
  • 15.
    • marble is another metamorphic rock
      • forms when limestone is squeezed and heated
    • slate
      • forms when shale is under great pressure
      • has layers
    • quartzite
      • forms from sandstone when heat melts the sand grains together
      • milky color
      • other minerals can give it a gray or pink color
  • 17. Summary
    • rocks are made up of one or more minerals
      • classified by how they are formed
    • igneous rocks form when magma or lava cools and hardens
    • sedimentary rocks made of pieces of rock that have been squeezed and stuck together
    • metamorphic rocks form when heat and pressure change rocks