1. Plate Tectonics

2. Review Earth’s Interior

3. Alfred Wegener (1880-1930) - German astronomer/meteorologist
- Proposed Continental Drift in 1912

4. Theory of Continental Drift
• Earth’s continents had once been joined as a single landmass called Pangaea “all lands”
• Broke apart 220 million years ago.

6. Pangaea Ultima?

7. Evidence from Rock Formations
- Same rocks are found in the Appalachians, Greenland and Europe.

8. Evidence from Fossils
- Wegener found similar fossils of different land animals and plants on separated continents.

9. Paleaoclimatology Evidence
- Coal
Coal forms from dead swamp plants.
Coal was found in Antarctica, therefore Antarctica must have been closer to the equator at one time.

10. More Paleaoclimatology Evidence
- Glacial Deposits
• 290 mya glacial deposits found in Africa, India, Australia, and South America.

11. Continental Drift was rejected.
- Scientists rejected the hypothesis because:
• People believed continents and ocean basins were fixed features.
• Wegener could not explain what forces could cause a continent to move.

12. Theory of Plate Tectonics (1960)
- Sea-Floor Spreading

13. New Technology - 1960s Technology:
• Magnetometer –map changes in magnetic fields.
Sonar – used to map out the seafloor (found mid-ocean ridge).
Radiometric Dating – ages the rocks.

14. Theory of Plate Tectonics Evidence
Rock Age
Young Rocks –near ocean ridges.
Older Rocks –near deep-sea trenches
Seafloor Age – oldest part = 180 million years old. Oldest Continental crust = 3.8 billion years old.
2. Paleomagnetism
• Investigated in ocean crust.
• Shows that iron alignment has switched many times in past due to Earth’s magnetic reversals, supporting movement of continents.

16. Major plates of the world.

17. Mechanism of Plate movement -Slab-pull and Convection.

18. Mid-ocean Ridge – crust is formed.

19. Subduction Zone – crust is destroyed.

20. Plate Boundaries Plate Boundaries Three Major Types Convergent
- places where tectonic plates interact with one another.
Convergent
plates come together.
Divergent
plates move away from one another.
Transform
plates move horizontally past one another

21. Divergent Boundary

22. Divergent - Iceland Rift

23. Convergent Oceanic- Continental Boundary

24. Oceanic-Continental Cascade Range

25. Cascade Range Volcanoes

26. Convergent Oceanic-oceanic Boundary

27. Convergent Continent-Continent Boundary

28. Continental-Continental Himalayas

29. Transform Boundary

30. Transform – San Andreas Fault

31. Know this drawing!