Plate Tectonics

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Plate Tectonics

• The Earths Crust in Motion

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The Theory
In 1910 Alfred begins to wonder
Whats the relationship? Perhaps all these
pieces used to be connected. Continental
driftslow movement over Earths surface 300
million years ago
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Supercontinent

• Pangea all lands
• Reptiles and insects
• Tropical forests
• -coal deposits

?Tens of Millions of years!
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Additional Evidence of Pangaea

• Shapes of continental margins
• Patterns of present-day animal life
• Similarities among far-distant fossils and rocks
• Evidence of past climates different from present
  climes for a region

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Structure of the Earths Interior
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The Crust
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The Earths Interior
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What are the plates?

• The plates are sections of the Earths crust and
  upper mantle.
• These two parts together are called the
  lithosphere.
• The lithosphere rides on top of another layer of
  upper mantle called the asthenosphere.
• The asthenosphere is a weaker layer.

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How does it work?
Plates pieces of the lithosphere Plates fit
closely together along cracks called Plate
Boundaries Convection Currents ? movement
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Earths Puzzle

• What plate do we live on?
• What plates do we border?
• USGS Earths Plates
• How far do we move every year?

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Types of Boundaries

• Divergent
• Convergent
• Transform

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• plates are moving apart
• new crust is created
• Magma is coming to the surface

• plates are coming together
• crust is returning to the mantle

• plates are slipping past each other
• crust is not created or destroyed

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2 oceanic plates or oceanic continental
?subduction
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Seafloor spreading
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Evidence for Sea Floor Spreading
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Convergent Boundaries
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The Big Picture
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Earthquakes around the World
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References

• eprentice.sdsu.edu/F044/mgarcia/presentation.ppt
• http//www.moorlandschool.co.uk/earth/magnetism.ht
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