1. Continental Drift Alfred Wegner’s theory

2. What was Wegner’s Theory?
The continents moved

3. What was his evidence? Jigsaw puzzle fit of the continents
Matching rocks & mountain chains
Similar fossils on different continents
A single glacier covering several continents
Paleomagnetism (continents aligned in different directions, not northward)

4. Theory of Plate Tectonics
Crust is made of 12 moveable lithospheric plates sitting and moving along the molten asthenosphere

6. What scientific evidence do we have to prove the cracks exist?

7. Last 30 Days of Earthquakes

9. Earthquakes occur along the plate boundaries!!

10. Evidence: 1. volcanoes and earthquakes occur in predictable regions (eg. Ring of Fire)

11. We know that the Earth has a magnetic field (North on top, South at the bottom)

12. Any iron found in newly made rock will point North

13. Once in a while, the Earth’s magnetic field reverses

14. Suppose North is now down “South”
…and the magnetism in the newly formed rocks will reverse

15. Exploring the Magnetic “stripes” on sea floor

17. But why are the magnetic stripes symmetrical?
There must be a crack in the ocean where the rocks are spreading outward

18. Evidence: 2. symmetrical magnetic stripes occur on either side of spreading mid-ocean ridges

19. Hawaiian Islands are not on the plate boundary. How did they form?

20. Hot Spot
The plate must be moving over the hot spot

21. Each island was formed one after the other

22. Evidence: 3. formation of the Hawaiian islands as the Pacific Plate moves over a central hot spot