Chapter 8: Major Elements

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Continental Drift

• Alfred Wegener (1912)
• First serious proponent
• Took time to look carefully at the data
  carefully study it
• Many scientists have ideas and don't follow up
• Many geologists were more familiar with the data,
  but couldn't bring themselves to believe it
• Wegener looked at the facts in the perspective of
  the theory looked for consistencies

Alfred manning the weather station, Greenland -
1913
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Fit of the Continents

• A modern view than Wegeners uses 1000 or 2000 m
  isobath as estimate of edge of continental crust

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Fit of Structural Elements
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Pennsylvanian (300 Ma) Glaciation
Glacial striations in bedrock, South Australia
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Pennsylvanian (300 Ma) Glaciation
Arrows indicate ice movement directions
Using present continental locations
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Pennsylvanian (300 Ma) Glaciation
Arrows indicate ice movement directions
Using pre-drift continental locations
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Fossil Evidence
Glossopteris an ancient seed fern (200 Ma)
Distribution of Glossopteris fossils
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Fossil Evidence
Distribution of Mesosaurus fossils
Mesosaurus couldnt swim in open ocean
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Paleomagnetism

• The Earth as a dipole

Magnetic declination and inclination
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Paleomagnetism

• Magnetization of volcanic rocks and sediments

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Paleomagnetism

• Polar Wandering curves

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• In spite of this data, the theory of continental
  drift died off in the 1950s, mainly because the
  geophysicists could not find an adequate
  mechanism to move the rigid crust and mantle