Plate Boundaries

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Plate Boundaries
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Destructive Plate Boundaries

• Also known as convergent boundaries or
  compressional boundaries.
• These cause violent volcanoes and earthquakes, as
  well as deep-ocean trenches and fold mountains.
• An oceanic plate and continental plate move
  towards each other.
• The denser oceanic plate dives under the lighter
  continental one, creating a deep ocean trench.

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Destructive Plate Boundaries

• As the oceanic plate goes deeper into mantle it
  melts in the subduction zone, due to friction and
  the increased temperature.
• The newly molten rock is lighter that that which
  surrounds it, so it will rise towards the surface
  and cause volcanoes on the earth's surface.
• The continental crust is crumpled by the
  collision of the two plates creating Fold
  Mountains.
• If the magma rises offshore it will form an
  Island Arc, like the West Indies and Japan.

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A good example of a destructive plate boundary is
where the Nazca plate dives underneath the South
American plate. This has caused volcanoes,
earthquakes and the formation of the Andes
Mountain Range.
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Constructive Plate Boundaries

• Also known as divergent or tensional boundaries.
• Although often not as violent as those on
  destructive plate boundaries, volcanoes and
  earthquakes do occur on constructive plate
  boundaries.
• They also cause mid-ocean ridges to form.
• Two plates move away from each other.
• Molten rock (magma) rises from the mantle to fill
  the gap between the two plates.
• This forms a mid-ocean ridge.

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Constructive Plate Boundaries

• Volcanoes can also form here, along the edges of
  the plate boundary, due to the rising magma.
• These volcanoes are called shield volcanoes.
• A good example of a constructive plate boundary
  can be found where the North American plate is
  moving away from the Eurasian plate.
• This has caused the Mid-Atlantic ridge to form
  and has created Iceland through volcanic activity.

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Constructive Plate Boundary
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Conservative Plate Boundaries

• Also known as passive plate boundaries.
• The main effects of a conservative plate boundary
  are earthquakes, which can be fairly violent and
  frequent.
• Two plates slide past each other, without
  creating or destroying any land.

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Conservative Plate Boundaries

• As they move past each other they often get
  stuck, building up great pressure until finally
  they jolt past each other.
• This sudden movement is what causes earthquakes.
• The best-known example of a conservative plate
  boundary is the San Andreas Fault, where the
  North American and Pacific plates are actually
  moving in the same direction, but at a different
  speed.

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Conservative Plate Boundaries
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Collision Margins

• Where two continental crusts collide neither can
  sink.
• Instead they push into each other forcing
  material to be folded up into huge mountain
  ranges.
• Often this movement and pressure can cause
  earthquakes, but no volcanoes will occur on these
  boundaries.
• The best example is found where the Indian plate
  collided with the Eurasian plate to form the
  Himalayas.

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Collision Margins