Continental Drift

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Continental Drift
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Continental Drift

• Some continents look like they fit like puzzle
  pieces
• Ex. South America and Africa
• Alfred Wegner proposed theory of continental
  drift.
• Continental drift, continents have moved slowly
  to their current locations.

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Pangaea

• Wegener proposed, 200 million years ago, the
  continents were one landmass.
• He called the landmass Pangaea.
• Pangaea meaning all land

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• Wegeners theory was highly controversial, due to
  his lack of proof.
• He proposed that continents plowed through the
  ocean floor because of the spin of the earth.
• It wasnt until the 1930s and after his death
  that his hypothesis was accepted, due to
  advancements in technology.

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Fossil Clues

• Fossil gave support to Wegners idea.
• Fossils of the reptile Mesosaurus have been found
  in South America and Africa.
• Another fossil that supports the hypothesis of
  continental drift is Glossopteris. found in
  Africa, Australia, India, South America, and
  Antarctica.

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Climate Clues

• Fossils of warm-weather plants were found on the
  island of Spitsbergen in the Arctic Ocean.
• Wegner hypothesized it drifted from a tropical
  region.

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Rock Clues

• Similar rock structures found on different
  continents.
• Appalachian Mountains similar to those found in
  Greenland and Western Europe.

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• Wegner, could not explain, when, why, or how.
• Move to How the Earth was made film

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Seafloor Spreading

• Sound waves used to measure depth of ocean floor
• Method used during World War II, and rifts,
  valley, and mountains were found.
• Looked similar to continents

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• In rift valleys, volcanic eruptions and
  earthquakes discovered.
• Ridges called mid-ocean ridges
• Harry Hess came up w/ Seafloor Spreading Theory.

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• Hot, less dense material rises toward the surface
  at the mid-ocean ridges.
• Then flows sideways, carrying the seafloor away
  from the ridge in both directions.
• This creates new seafloor.
• New seafloor closer to ridge
• Older seafloor moves away from ridge

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Magnetic Clues

• http//www.youtube.com/watch?vGyMLlLxbfa4feature
  related
• Magnetic poles will reverse themselves. South
  becomes North and North becomes South.
• Rock samples along the ridge demonstrate this
  change in polarity over time.

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• Parallel line of rock, demonstrates normal and
  reverse polarity on each side of the ridge.
• http//www.youtube.com/watch?vBCzCmldiaWQ

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• __________ is the hypothesis that continents have
  slowly moved to their current locations.
• A. Continental drift
• B. Mid-ocean shifting
• C. Pangaea
• D. Seafloor spreading

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• Who proposed the hypothesis of continental drift?
  
• A. Esker
• B. Gagarin
• C. Hess
• D. Wegener

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• What is Pangea?
• Pangaea means all land and is the name that
  Wegener used to refer to the one large landmass
  that he believed existed before it broke apart
  into continents.

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• What is seafloor spreading?
• Seafloor spreading is the process in which hot,
  less dense material below Earths crust rises
  toward the surface at the mid-ocean ridges. This
  material flows sideways and carries the seafloor
  away from the ridge in both directions.

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• How did scientists realize that the ocean floor
  was not flat, and what did they discover?
• During WWII, the military used sonar to look for
  submarines. What they found were different
  depths, which when compiled, showed, canyons and
  mountains like that on earth.