12.1 Evidence for Continental Drift

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12.1 Evidence for Continental Drift

• If you look closely at a world map. It looks
  likes S. America and Africa can fit together.

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12.1 Evidence for Continental Drift

• Early maps of the world caused Alfred _________
  to propose
• the ____________________________.
• The continents looked as though they might fit
  together like puzzle pieces.
• The continental shelves actually fit together
  even better.
• The large mountain ranges and coast lines match
  up. Each continent has a continental shelf
• Continent
• Continental shelf
• 
  Ocean floor
• All continental shelves are approximately 200m
  deep.

See pages 506 - 509
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12.1 Evidence for Continental Drift

• The original, supercontinent was named _________
  by Wegener.
• Wegener also realized that other evidence also
  supported his theory.
• 1. There were ___________________________ and
  ________ on different continents.
• Rocks in Newfoundland are the same type rock with
  the same age as the rocks in Norway and Sweden
• 2. There were _________ _________, like
  Mesosaurs, on different continents.
• Similar fossils found at similar depths in Africa
  and South America. Plants and animals are only
  found in very specific locations around the
  world.

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12.1 Evidence for Continental Drift

• 3. There was evidence of different climates (eg.
  glaciers) on warm continents.
• Fossils of warm weather plants found in
  Antarctica Glacial rock in S. America and Africa.
  
• Ice ages show the retreat of large icebergs.
  These icebergs leave behind deep valleys and
  scratches in the ground.
• There is coal in Antarctica coal comes from
  decaying tropical swamp land. If Antarctica was
  a swamp land then it must have been in another
  location on the earth.

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Quick Check

• 1. What did Wegener notice about the shapes of
  continents that led him to suggest that
  continents were able to move? ____________________
  __________________________________________
• __________________________________________________
  _____________________
• 2. List three forms of evidence besides continent
  shape that gave support to the idea of
  continental drift.
• __________________________________________________
  ______________________
• __________________________________________________
  ______________________
• __________________________________________________
  ______________________

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Continental drift theory - Pangea breaking
apart
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How Can Continents Move?

• Wegeners evidence for continental drift didnt
  explain
• how entire continents could change locations.
• New scientific equipment ( ________) allowed
  scientists to measure the slow, but steady, drift
  of Earths tectonic plates.
• It was noted that ____________ and ____________
  appear in certain patterns, which happen to be
  along the ______________________
  ___________________.
• Mapping of the ocean floor revealed the
  __________________, a long mountain range running
  down the middle of the Atlantic ocean.

See pages 510 - 512
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How Can Continents Move?

• Rocks taken from the Mid Atlantic ridge were
  ______________ than other ocean rocks.
• Sediments along the Ridge became
  ________________________ ____________ from the
  ridge.
• _______________________ shows that iron-based
  rocks along the ridges are striped with reversing
  magnetic fields.
• All of these findings developed the
• Theory of _______________________

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Sea Floor Spreading
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Sea Floor Spreading An Explanation

• Hess suggested that magma rose to form new rock
  at certain places.
• Magma (melted rock), rises and falls like warm
  and cold liquids.
• The __________________________________ formed a
  _______________________ where it broke through
  Earths crust.
• Like a new crust conveyer belt
• Magnetic striping of basalt rock shows long
  stripes of new rock moving away from ocean
  ridges, and also reveals the direction of Earths
  magnetic field at that time. This magnetic field
  changes or reverses over time.

See pages 512 - 513
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• Wilson then unified the ideas of Wegener and Hess
  into the plate tectonic theory.
• Continental drift occurs because of areas like
  these ridges, that push along tectonic plates
  floating on Earths surface.
• geologic ______________ are anywhere magma rises
  to Earths surface.
• A geologic hot spot is the location of
  ____________________, causing magma to rise to
  Earths surface.
• The __________ Islands formed as a
  tectonic plate passed over a hot spot and magma
  rose up from under Earths surface.

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Plate Tectonics - 1960
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Quick Check

• Quick Check
• 1. Explain the implications of evidence from each
  of the following areas.
• (a) mapping the sea floor ________________________
  _________________________________
• __________________________________________________
  __________________________
• __________________________________________________
  __________________________
• (b) analyzing ocean rock and sediments
  _____________________________________________
• __________________________________________________
  __________________________
• __________________________________________________
  __________________________
• (c) paleomagnetism _______________________________
  ______________________________
• __________________________________________________
  __________________________
• __________________________________________________
  __________________________
• 2. How did the Hawaiian Islands form?
  _________________________________________________
• __________________________________________________
  _____________________________
• __________________________________________________
  _____________________________
• 3. What does the theory of plate tectonics state?
  _________________________________________
• __________________________________________________
  _____________________________
• __________________________________________________
  _____________________________