Alfred Wegener's Theory of Continental Drift

Alfred Wegener's Theory of Continental Drift

1. Wasn't excepted because...

   • Movement wasn't detectable.
   • He wasn't a geologist, he was a meteorologist.
   • It was just after the war and Wegener was German.
   • His possible explanations on why drifting happened were deemed impossible.
     • Movement could be caused by...
       • The Earth's rotation.
       • Tidal forces.

2. It explained...

   • Why similar fossils of plants and animals had been found on opposite sides of the Earth.
   • Mountain building which happened when continents smashed together.

3. Instead it was believed...

   • Continents used to be linked by land bridges.

4. His theory...

   • Africa and South America had been one continent which then split.
   • 300 years ago there was a supercontinent called Pangaea.
   • The continents are moving apart.

5. It was proven correct in the end because...

   • In the 1950's, scientists investigated the Mid-Atlantic Ridge.
     • Evidence that magma rises up through the sea floor, solidifies and forms underwater mountains that are roughly symmetrical either side of the ridge was found.
       • This suggested that the sea floor was spreading.
   • Magnetic orientation of the rocks.
     • As liquid magma erupts out of the gap, iron particles in the rocks tend to align themselves with the Earth's magnetic field.

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