Unit Six Notes

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Plate Tectonics
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Looking at the world map, what do you notice
about the shape of the continents?
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The thing isthe world didnt always look like
this! It used to look like this
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How is this possible?!?!?
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Plate Tectonics Theory

• The earth is divided into a number of large and
  small plates and the plates are floating on the
  mantle

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Can you see the direction of movement?
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What about the tectonic map, see anything sneaky?
What major physical features does this map show?
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Plate Boundaries

• In some places of the world, plates move away
  from each other. This is because magma from the
  mantle spreads open the ocean floor.

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• Divergent boundary

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This is an area of Iceland where two pieces of
land are getting further from each other.
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• Some plates are moving toward each other and are
  colliding

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When Ocean Plates collide with Contintental Plates

• Can Create near coast volcanoes
• Can create earthquakes

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When a continental plate collides with another
continental plate

• Mountain ranges are created
• (example Himalayan Mountains)

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Himalayan Mountains
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• Sometimes plates are neither moving toward nor
  away from each other, they are moving past one
  another.

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Transform Fault Boundary

• The plates may move in opposite directions or in
  the same directions but at different rates and
  frequent earthquakes are created (example San
  Andreas Fault)

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San Andreas Fault
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So is the Earth getting bigger?

• No
• Plates are destroyed as fast as they are created
  (2 ways)
• Plates may be subducted and melted or may push be
  pushed upward to form mountains

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What causes this?

• Convection currents within the mantle

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Speed of Spreading

• Atlantic Ocean 2-3 cm/year
• South Pacific Ocean 15-18 cm/year

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Continental Drift Theory

• The continents have shifted their position over
  geologic time

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• At one time all land masses were connected into
  one piece called Pangaea