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.
Mapped volcanoes and earthquakes along plate boundaries.
Sonar – used to map out the seafloor (found mid-ocean ridge).

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
• Found in new ocean crust.
• Shows that iron alignment has switched many times in past, supporting movement of continents.

16. Geomagnetic Time Scale
Magnetic Reversal
Normal Polarity
Reversed Polarity
a change in Earth’s magnetic field.
a magnetic field that has the same orientation as Earth’s present field
a magnetic field that is opposite to the present field

17. Theory of Plate Tectonics Evidence continued….
2. Paleomagnetism is the past formation of rocks containing iron and show the direction of polarity of Earth’s magnetic field.

18. Major plates of the world.

19. Mid-ocean Ridge – crust is formed.

20. Subduction Zone – crust is destroyed.

21. Slab-pull and Convection Currents cause plate motion.

22. 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

23. Divergent Boundary

24. Divergent - Iceland Rift

25. Convergent Oceanic- Continental Boundary

26. Oceanic-Continental Cascade Range

27. Cascade Range Volcanoes

28. Convergent Oceanic-oceanic Boundary

29. Convergent Continent-Continent Boundary

30. Continental-Continental Himalayas

31. Transform Boundary

32. Transform – San Andreas Fault

33. Know this drawing!