Metamorphic Rocks

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Metamorphic Rocks

• Chapter 4 Section 3

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Metamorphic Rocks

• Rocks that have changed because of changes in
  temperature and pressure or the presence of hot
  fluids are called metamorphic rocks.
• Metamorphic rocks can form from igneous,
  sedimentary, or other metamorphic rocks.

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Heat and Pressure

• Temperature and pressure increase with depth in
  the Earth.
• In some areas, heat and pressure cause rocks to
  melt and magma to form.
• In other areas, melting doesnt occur, and
  mineral grains can change by dissolving and
  recrystallizing. Minerals may exchange atoms with
  surrounding minerals and form new, bigger
  minerals. These processes form metamorphic rocks.
• One type of rock can change into several
  metamorphic rocks depending upon the amount of
  pressure and heat. Ex. Shale can change to slate,
  which can change to phyllite, then to schist,
  then to gneiss.

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Slate
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Hot Fluids

• Water with dissolved elements and compounds can
  react chemically with a rock and change its
  composition, especially when fluids are hot.
• Rock surrounding a hot magma body reacts with hot
  fluids from the magma, forming metamorphic rock.
  This is called contact metamorphism.

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Foliated Rocks

• Metamorphic rocks are classified according to
  their texture and composition.
• When mineral grains line up in parallel layers,
  the metamorphic rock has foliated texture.
• Two examples of foliated rocks are slate, formed
  from the sedimentary rock shale, and gneiss,
  formed from the igneous rock granite.
• -Slate separates easily along the foliation
  layers, and the minerals in slate are pressed
  together so tightly that water cant pass between
  them easily.
• -Foliation in gneiss shows up as alternation
  light and dark bands.

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Slate Again!!
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Gneiss
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Nonfoliated Rocks

• In a nonfoliated metamorphic rock, the mineral
  grains grow and rearrange, but they dont form
  layers.
• Quartzite is a nonfoliated metamorphic rock
  formed from sedimentary rock sandstone.
• Marble is another nonfoliated rock formed from
  the sedimentary rock limestone.

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Marble