Plate Tectonics

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Plate Tectonics

• plate tect BN.asf

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• Wegeners theory of continental drift was not
  accepted because he did not have a good
  explanation or mechanism for how it worked. He
  used

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1. The fit of the continents

• The continents fit like puzzle pieces.

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2. Fossils

• Fossils of the same dinosaur were found on
  different continents (South America and Africa).
• Fossils of the same plant were found in many
  different locations (Africa, Australia, India,
  South America and Antarctica).

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3. Past Climate Conditions

• Fossils of warm weather plants were found in cold
  locations (like the Arctic Ocean)
• Evidence of glacial activity can be found in
  South America, Africa, India, and Australia.

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4. Rocks and Common Geologic Features

• - Similar rock structures can be found in
  Greenland and the eastern U. S. and also in South
  America and Africa.

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Plate Tectonics

• Developed around 1950 to explain the motion of
  the plates and the position of the continents.
• Further evidence was identified to support
  Wegners theory and a mechanism was discovered to
  explain how/why the plates move.

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1. Seafloor Movement

• New land is added on the sea floor at divergent
  boundaries and as a result, the sea floor spreads
  apart.
• (Mid-ocean Ridges form at these divergent
  boundaries)

http//www.suu.edu/faculty/colberg/Hazards/PlateTe
ctonics/30_SeaFloor.html
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2. Age of rocks on the ocean floor

• Rocks near the mid-ocean ridges are younger than
  those farther away

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3. Paleomagnetism

• Over time the Earths magnetic poles have
  reversed.
• When the poles reverse, iron minerals align
  themselves with the Earths magnetic pole.
• Scientists have found rocks on the ocean floor
  that showed many magnetic reversals.

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4. Locations of hot spots

• Hot spots are stationary
• Scientists can track the movement of a plate by
  looking at the position of a hot spot.

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• http//www.suu.edu/faculty/colberg/Hazards/PlateTe
  ctonics/18_Pangaea.html