The Theory of Plate Tectonics

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The Theory of Plate Tectonics
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Tectonic Plates

• Tectonic Plates are pieces of lithosphere that
  move around on the Athenosphere.
• Plates range in size.
• Some plates contain both continental and oceanic
  crust.
• Plates link like a puzzle.

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Tectonic Plate Boundaries

• A Plate Boundary is the place where two plates
  meet.
• There are 3 types of boundaries.
• Convergent
• Divergent
• Transform

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Convergent Plate Boundaries

• At Convergent boundaries two plates collide.
• Three results may happen from the collision.
• The type of plates that collide will determine
  one of three geographic features.

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Convergent Plate Boundaries

1. If two continental plates collide, a high
   mountain range may form.
2. The mountain may take many of years to form.

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Convergent Plate Boundaries

1. When a plate of oceanic lithosphere collides with
   a plate of continental lithosphere, the denser
   oceanic lithosphere sinks, or subducts beneath
   the less dense continental crust.
2. This process is called subduction.
3. Subduction may cause a chain of volcanoes to form
   parallel to the fault.

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• When two oceanic plates collide, the denser of
  the two will submerge.
• A series of volcanic islands called island arc
  may form parallel to the fault.

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Divergent Plate Boundaries

• Where two tectonic plates separate.
• Some appear on land.
• Most appear on sea floor.
• As plates spread, magma rises to the ocean floor.
  
• The magma cools and forms new lithosphere.

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Transform Plate Boundaries

• Two tectonic plates slide past each other.
• Most transform boundaries occur in the sea floor
  at mid-ocean ridges.
• San Andreas Fault in California occurs both on
  land and in the ocean.

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San Andreas Fault
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Causes of Tectonic Plate Motion

• Heat is transferred from the Earths core through
  convection.
• When rock is heated, it becomes less dense and
  moves towards the surface. At the surface, cooler
  dense rock tends to sink thru subduction.
• Convection currents are formed all over the
  mantle, causing plates to move.

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Tracking Tectonic Plate Motion

• Plates move so slow that they are measured in
  centimeters per year.
• Scientists use GPS and satellites to measure
  exact distances.
• Scientists use sea floor spreading to measure
  ocean plates.

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