MOVING CONTINENTS

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MOVING CONTINENTS

• Theory of Continental Drift

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Alfred Wegener
-German Meteorologist -Jigsaw Puzzle
effect -Fossil Evidence -Centrifugal Force
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Continental Drift Theory

• Alfred Wegener (1880 - 1930)
• German meteorologist suggested in 1912 that
• continents have moved slowly to their current
  positions
• PANGAEA 250 m.y.a. all continents were once
  connected as one large land mass
• GONDWANA LAURASIA - 180 - 200 m.y.a. land
  mass broke apart, and the Earths continents
  began drifting to present locations

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PANGAEA
GONDWANA LAURASIA
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Continental Drift
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History of Continental Drift Theory

• Thoughts about continental drift had been around
  for a very long time
• Sir Francis Bacon in the early 1600s had written
  about it
• Most based theory on deduction and small pieces
  of evidence
• Wegner gathered a larger and more complete body
  of evidence

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Evidence for Continental Drift

• JIG SAW PUZZLE-like fit of the continents
• FOSSILS similar fossils on different continents
• Glossopteris - ferns
• Lystrosaurus reptile fossils found in S.
  Africa, Antarctica, India, China
• Warm weather plant fossils found in Arctic
  regions
• GLACIAL DEPOSITS found in areas presently in
  the tropics

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Fossil Evidence
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Glacial Evidence
Grooves carved by glaciers (shown by arrows)
provided evidence for continental drift.
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More Evidence

• Similar rock structures on different continents
• COAL BEDS
• MOUNTAIN RANGES
• rocks on the east coast of S. America match those
  on the west coast of Africa, tests reveal they
  formed at the same time (550 mya)
• belt of mountains along the east coast of N.
  America match those existing in northern Europe

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MOUNTAIN RANGES

• Explanation for their existence
• Cooling, Contracting-Earth Theory
• they formed on the Earth's crust as wrinkles form
  on the skin of a drying apple. If this were so,
  however, they should be spread evenly over the
  Earth instead mountain ranges occur in narrow
  bands, usually at the edge of a continent.
• Continental Drift (WEGENER)
• Mountains formed when the edge of a drifting
  continent crumpled and foldedas when India hit
  Asia and formed the Himalayas.

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Similar Layers of Rock
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Mountain Chains
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No Support for Continental Drift?

• Flaws with theory at the time
• Earths crust was believed to be too rigid
• No suitable mechanism to provide enough energy to
  move the continents such great distances could be
  identified Earth does not spin fast enough!

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Continental Drift NOT Accepted

• NOT accepted because how or why
• continents had moved could not be
• explained!!
• Wegner tried to base movement of continents on
  gravitational pull and centrifugal force!
• The fact that Wegner was a meteorologist led some
  people to not believe his thoughts on geology
  particularly when he could not provide evidence
  to support his hypothesis.

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Why wasnt the Theory of Continental Drift
Accepted?
METEOROLOGIST vs. GEOLOGIST
DRIVING FORCE CENTRIFUGAL FORCE OF
THE EARTH. (Not believed to be strong enough.)
http//earthobservatory.nasa.gov/Features/Wegener/
wegener.php Nice biography of Alfred Wegener