Rock Types And Classifications

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Rock Types And Classifications
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Igneous

• Igneous rocks are fire formed
• They originate from the magma in the mantle of
  the Earth.
• Extrusive igneous rocks are formed by being
  thrown out during a volcanic eruption.
• They cool very quickly once they reach the
  surface.
• An example of an extrusive igneous rock is
  basalt.
• Intrusive igneous rocks are formed under the
  surface of the earth, cooling very slowly to form
  a large area of rock under the surface of the
  earth.
• An example of an intrusive igneous rock is
  granite.

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Igneous Rock
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Sedimentary

• Over millions of years the actions of rivers,
  glaciers and the wind produce large amounts of
  small particles called sediments.
• These accumulated on sea floors in layers, and
  due to the pressure of material above they were
  compressed to form rocks.

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Sedimentary Rock
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Sedimentary Rock Types

• Sandstone, which is made from compressed sand.
• Clay, which is made from compressed mud.
• Coal, which is made from the compressed remains
  of ancient forests.
• Chalk and limestone, which is made from the
  compressed remains of plants and animals.

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Metamorphic Rocks

• Rocks which have been changed in shape or form,
  usually by heat or pressure, are called
  metamorphic rocks.
• They begin as either igneous or sedimentary rocks
  before being changed, usually in areas of high
  pressure and intense heat, such as plate margins.
• Examples include slate (which used to be clay)
  and marble (which used to be limestone).

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Metamorphic Rock
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The Rock Cycle