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Continental Drift

2. Continental Drift Alfred Wegner – German scientist
1912 – proposed idea of Pangaea
Super Continent
All Lands
Continents “fit” like a puzzle

3. Continental Drift Pangaea broke apart and moved into present positions
Still moving
Continental Drift – movement of continents
Most thought he was wrong

4. Fossil and Climate Clues
Similar fossils found on separate continents
Glossopteris (plant) – Africa, S.A., Australia, Antarctica
Mesosaurus (reptile) – Africa and S.A.

6. Fossil and Climate Clues
Africa and S.A. – glacier evidence
Antarctica – once had a tropical climate
Fossil evidence

10. Rock Clues Similar rocks on different continents
Scotland and Newfoundland – Same rock structure
Similar mountain ranges across oceans
Joined 250 million years ago

11. Why? Wegner couldn’t figure out what made the continents move.
Many scientist didn’t take him seriously.
Years later technology gave an answer to why.

12. Mid-Ocean Ridge Underwater mountain chain Valley in center
Sediment thinner by ridge
Rocks older farther away

14. Harry Hess US Naval Officer in WWII “Sea floor spreading”
New sea floor at ridge

15. Seafloor Spreading Magma oozes out onto ocean floor
Plates move away from each other
Sea Floor Spreading - New crust forms

16. Seafloor Spreading
North American Plate is moving away from European and African Plate

21. Paleomagnetism Magnetic minerals on ocean floor
Mirrored alternating magnetic stripes on either side of ridge