Plate Tectonics

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Plate Tectonics
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Aim How does the Theory of Plate Tectonics
influence the way the Earth is today?
I. Plate Tectonics
A. Theory of Plate Tectonics
1. The surface of the Earth is composed of about
a dozen major rigid, moving crustal plates and
several smaller plates
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• Plates
• a. Slabs of Earths lithosphere (crust and
  upper mantle)
• b. Average thickness is 100 km (62 miles)
• c. Most plates support both continent and ocean

B. Continental Drift states that the
continents have drifted and still are drifting
apart.
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C. Why do the plates move?

• Due to tremendous heat, rock in the asthenosphere
  is like hot taffy
• This allows plates to ride on top of hot, flowing
  rock.
• 3. Plates move because heat is being released
  from deep inside the earth.
• 4. Convection currents causes hot material to
  rise and expand (plates diverge) and cooler
  material to sink and contract (plates converge).

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Alfred Wegener
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D. Alfred Wegener proposed that in the distant
past, the Earths continents were all joined as a
single landmass.
1. Evidence for his theory

• South America and Africa would fit remarkably
  well, shoreline to shoreline.
• If the Americas were moved next to Africa and
  Europe, there would be a match of ancient
  continental rocks and tectonic (fold and fault)
  structures.
• c. Pangaea when Wegener placed all the
  continents together like a puzzle, it formed a
  large landmass which he called Pangaea.

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Fossil Evidence
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GIF image 240x180 pixels
http//www.hartrao.ac.za/geodesy/tectonics.html
Animated Plate Tectonic Reconstruction
http//pubs.usgs.gov/publications/text/dynamic.htm
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http//www.geocities.com/jac6610805
http//wrgis.wr.usgs.gov/docs/parks/animate/A14.gi
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http//wrgis.wr.usgs.gov/docs/parks/animate/A08.gi
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http//www.ucmp.berkeley.edu/geology/anim1.html
http//www.eram.k12.ny.us/education/sctemp/7dc4527
a049452e89e289cec62ecb878/tectonics.swf
http//www.ucmp.berkeley.edu/geology/anim11.html
http//wrgis.wr.usgs.gov/docs/parks/animate/PLATES
_3.MPG