1. Continental Drift and Plate Tectonics

2. Take-Away Points How we know plate tectonics happens
Most earthquakes and volcanoes occur along plate boundaries
New ocean crust is created along mid-ocean ridges
Old ocean crust is recycled at subduction zones
Subduction zones are where mountain-building (orogeny) occurs
Small pieces of crust (terranes) are important in building up continents
Hot spots are long lived stationary magma sources

3. Global Problems in Geology
Distribution of Continents
Mid-ocean Ridges
Trenches
Orogenic Belts
Deformation
Metamorphism
Volcanism
Earthquakes

4. Development of Continental Drift
Lots of people had noticed that the coastlines of Africa and South America are similar
Frank Taylor (1910)
Alfred Wegener (1912) Die Entstehung Der Kontinente Und Ozeane
1. How we know plate tectonics happens

5. The Permian Ice Age Problem
1. How we know plate tectonics happens

6. 1. How we know plate tectonics happens
Wegener’s Theory
1. How we know plate tectonics happens

7. 1. How we know plate tectonics happens
Dating the Breakup
1. How we know plate tectonics happens

8. 1. How we know plate tectonics happens
Frank Taylor
In some respects, Taylor’s ideas were more modern than Wegener’s
Taylor always thought Wegener had stolen credit from him
1. How we know plate tectonics happens

9. 1. How we know plate tectonics happens
Frank Taylor
Recognized role of Mid-Atlantic Ridge
Never reconstructed the continents like Wegener did
1. How we know plate tectonics happens

10. Confirmation of Continental Drift
World War II technology
International Geophysical Year (IGY)
Worldwide Standardized Seismic Network 1963-
1. How we know plate tectonics happens

11. The Geomagnetic Reversal Time Scale
1. How we know plate tectonics happens

12. Discovery of Sea-Floor Spreading
1. How we know plate tectonics happens

13. 1. How we know plate tectonics happens
Sea-Floor Spreading
1. How we know plate tectonics happens

14. Where Does Ocean Crust Go?
Hugo Benioff, 1954
1. How we know plate tectonics happens

15. Benioff’s Interpretation
1. How we know plate tectonics happens

16. Benioff’s Interpretation Updated
1. How we know plate tectonics happens

17. Worldwide Standardized Seismic Network
2. Most earthquakes and volcanoes occur along plate boundaries

18. The Plate Tectonics Model

19. The Plate Tectonics Model

20. The Earth’s Plates

21. Global Plate Motions

22. What Drives It: Convection

23. How Plates Move

24. Reconstructing Plate Movements

25. Fit of Continents Across the Atlantic

26. Present Day Atlantic

27. Atlantic 65 m.y. ago

28. Geology of Plate Margins

29. Ophiolites: Oceanic Crust

30. Anatomy of a Mid-Ocean Ridge

31. FAMOUS: Close-Up of the Mid-Atlantic Ridge

32. Magnetic Stripes in the FAMOUS Area

33. A Subduction Zone

34. Why Mountains are High

35. Where the Plates Meet

36. Terrane Accretion

37. Terranes in Western North America

38. Plate Boundaries and Earthquakes

39. Hot Spots

40. Hot Spots: Hawaii

41. Pacific Hot Spot Tracks