Plate Tectonics

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Plate Tectonics

• Our Dynamic Planet

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Continental Drift

• In 1912, a German scientist (he was an explorer,
  astronomer, and meteorologist) proposed that at
  one time all of the continents had been joined
  together to form one huge continent
• His name was Alfred Wegener
• He called this supercontinent Pangaea (it means
  all Earth)
• And, over time (millions of years), the
  continents slowly drifted apart and ended up in
  the positions we see on Earth today

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Continental Drift
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Continental Drift

• Wegener could even provide 6 pieces of evidence
  to support his claim
• 1) Continents seem to fit together like pieces of
  a jigsaw puzzle
• 2) Fossils of the same organisms are found on
  different continents
• 3) Plant fossils (ferns) have been found under
  Antarctic ice! (Whats so weird about that??)

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Continental Drift

• 4) Spotted cats are found in South America
  (jaguars and ocelots) and Africa (panthers and
  leopards)
• How did they get on 2 different continents did
  they swim across the Atlantic Ocean?
• Also Similar bird species found on 3 different
  continents
• Ostrich (Africa), Rhea (S. America), and Emu
  (Australia)

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Continental Drift

• 5) Veins of certain minerals appear to begin in
  one continent and end in another
• For example, diamonds in Brazil and S. Africa
• 6) Mountain ranges in N. America and Europe line
  up
• Also, scars from glaciation appear on opposite
  continents

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Continental Drift
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Continental Drift Matching Mountain Ranges
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Continental Drift Glacier Evidence
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Continental Drift

• Wegeners idea was ridiculed by geologists
• This is because while Wegener could provide
  evidence, he couldnt provide an actual mechanism
  an Earth PROCESS that could cause huge land
  masses to move across the globe
• However, new technology finally led to findings
  to support Wegeners theory
• Ultimately a new theory was formed called Plate
  Tectonics

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What is Plate Tectonics?

• Earths upper mantle and crust are composed of
  solid, rigid rocks
• This uppermost region is called the LITHOSPHERE
• The lithosphere is broken up into separate
  sections called plates
• These plates (there are about 12) move over the
  less rigid (more fluid) material of the
  ASTHENOSPHERE (the lower mantle)

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