Plate Tectonics: A Scientific Revolution Unfolds Chapter 7

1. Plate Tectonics: A Scientific Revolution UnfoldsChapter 7

2. What evidence was used to support the continental drift hypothesis? What was one of the main objections to the continental drift hypothesis? What is the theory of plate tectonics? In what major way does the plate tectonics theory depart from the continental drift hypothesis? Focus on Concepts

3. What are the three types of plate boundaries? Where does new lithosphere form? How do mountain systems such as the Himalayas form? What type of plate motion occurs along a transform fault boundary? Focus on Concepts

4. What evidence is used to support the plate tectonics theory? What are the major driving forces for plate tectonics? What models have been proposed to explain the driving mechanism for plate motion? Focus on Concepts

5. 7.1From Continental drift to Plate Tectonics

6. The collision of India and Asia produced the Himalayas

7. K7 in Pakistan’s Karakoram (Himalayas)

8. 7.2Continental Drift: An idea before its time

9. Alfred Wegener • Pangaea • Continental Drift Hypothesis

10. Eduard Suess Gondwana

11. Began in early Mesozoic (~200 mya) • Evidence • Continental jigsaw puzzle • Fossil distribution • Rock types & geologic features • Ancient climates Continental Drift Hypothesis

12. Continental Jigsaw Puzzle

13. Continental Jigsaw Puzzle

14. Evidence

16. Fossil Distribution

17. Fossil Distribution

18. Beardmore Glacier Location of the fossil site at the Oliver Bluffs on the Beardmore Glacier

19. There are rock formations (such as mountain ranges) on different continents that match up beautifully when the continents are put back together. Rock Types & Geologic Features

20. Rock Types & Geologic Features

21. Paleoclimatic data Extreme global cooling? Wegener’s explanation Ancient Climates

22. Glacial Striations

23. Post-Drift Ice Sheets

24. Pre-Drift Ice Sheet

25. 7.3The Great Debate

26. What mechanism allows movement? Not all evidence supported the hypothesis. Some thought the idea was intriguing or an answer to a previously unexplained phenomena. Objections to the Continental Drift Hypothesis

27. Objections to the Continental Drift Hypothesis

28. 7.4Plate Tectonics

29. 1968; more encompassing than CDH Lithosphere broken into plates, slide over asthenosphere Plate tectonics theory

30. Earth’s Major tectonic Plates

31. LARGE – 94% of Earth’s S.A. • North American • South American • Pacific • African • Eurasian • Australian-Indian • Antarctic Earth’s Major tectonic Plates

32. INTERMEDIATE – mostly oceanic • Caribbean • Nazca • Phillipine • Arabian • Cocos • Scotia • Juan de Fuca Earth’s Major tectonic Plates

33. Divergent (constructive) Convergent (destructive) Transform (conservative) Plate Boundaries

34. Plate Boundaries

35. Plate Boundaries

36. 7.5Divergent Boundaries

37. “spreading center” constructive plate margin Divergent Boundaries

38. Elevated are of seafloor characterized by high heat flow, volcanism Rift valley @ center of ridge is proof that tensional forces are pulling the ridge apart Oceanic Ridges

39. Oceanic Ridges

40. Oceanic Ridges

41. Average 5 cm/year • New ocean crust is hot • Less dense • Rises Seafloor Spreading

42. Seafloor Spreading

43. Opposing tectonic forces pull the lithosphere apart Continental Rifting

44. Brittle rocks break into large slabs Continental Rifting

45. East African Rift

46. East African Rift Mt. Kilimanjaro

47. East African Rift

48. East African Rift

49. Continental Rift

50. Continental Rift