1. Understanding Earth Fifth Edition Chapter 2: Plate Tetonics: The Unifying Theory Copyright © 2007 by W. H. Freeman and Company Grotzinger Jordan Press Siever

2. Divergent Boundaries Oceanic Plate Separation Mid- Atlantic Ridge North American Plate North American Plate Eurasian Plate Eurasian Plate

3. Divergent Boundaries Oceanic Plate Separation Mid- Atlantic Ridge North American Plate North American Plate Eurasian Plate Eurasian Plate Volcanoes and earthquakes concentrate.

4. Divergent Boundaries Continental Plate Separation East African Rift Valley Somali Subplate African Plate

5. Divergent Boundaries Continental Plate Separation East African Rift Valley Somali Subplate African Plate Parallel valleys; volcanoes and earthquakes.

6. Convergent Boundaries Ocean-Ocean Convergence Mariana Islands Marianas Trench Pacific Plate Philippine Plate Philippine Plate

7. Convergent Boundaries Ocean-Ocean Convergence Mariana Islands Marianas Trench Pacific Plate Philippine Plate Philippine Plate Deep-sea trench; volcanic island arc.

8. Convergent Boundaries Ocean-Continent Convergence Nazca Plate Andes Mountains South American Plate South American Plate Peru-Chile Trench

9. Convergent Boundaries Ocean-Continent Convergence Nazca Plate Andes Mountains South American Plate South American Plate Peru-Chile Trench A volcanic belt of mountains forms.

10. Convergent Boundaries Continent-Continent Convergence Himalaya Main thrust fault Tibetan Plateau Indian-Australian Plate Eurasian Plate Eurasian Plate

11. Convergent Boundaries Continent-Continent Convergence Himalaya Main thrust fault Tibetan Plateau Indian-Australian Plate Eurasian Plate Eurasian Plate Crust crumbles, creating high mountains and a wide plateau.

12. Transform-Fault Boundaries Mid-Ocean Ridge Transform Fault North American Plate Eurasian Plate

13. Transform-Fault Boundaries Mid-Ocean Ridge Transform Fault North American Plate Eurasian Plate Spreading centers offset.

14. Transform-Fault Boundaries Continental Transform Fault North American Plate Pacific Plate

15. Transform-Fault Boundaries Continental Transform Fault North American Plate Pacific Plate Offset continental crust.

17. As plates move past each other...

18. As plates move past each other... …creek beds are offset

19. As plates move past each other... …creek beds are offset San Francisco Los Angeles San Andreas fault

20. Magnetic mapping can measure the rate of seafloor spreading An oceanic survey over the Reykjanes Ridge, part of the Mid-Atlantic Ridge southwest of Iceland, showed an oscillating pattern of magnetic field strength. This figure illustrates how scientists worked out the explanation of this pattern. Mid-Atlantic Ridge High intensity Low intensity

21. Magnetic mapping can measure the rate of seafloor spreading An oceanic survey over the Reykjanes Ridge, part of the Mid-Atlantic Ridge southwest of Iceland, showed an oscillating pattern of magnetic field strength. This figure illustrates how scientists worked out the explanation of this pattern. Mid-Atlantic Ridge High intensity Low intensity A sensitive magnetometer records magnetic anomalies,…

22. Magnetic mapping can measure the rate of seafloor spreading An oceanic survey over the Reykjanes Ridge, part of the Mid-Atlantic Ridge southwest of Iceland, showed an oscillating pattern of magnetic field strength. This figure illustrates how scientists worked out the explanation of this pattern. Mid-Atlantic Ridge High intensity Low intensity A sensitive magnetometer records magnetic anomalies,… Iceland Mid- Atlantic Ridge

23. Magnetic mapping can measure the rate of seafloor spreading An oceanic survey over the Reykjanes Ridge, part of the Mid-Atlantic Ridge southwest of Iceland, showed an oscillating pattern of magnetic field strength. This figure illustrates how scientists worked out the explanation of this pattern. Mid-Atlantic Ridge High intensity Low intensity A sensitive magnetometer records magnetic anomalies,… Iceland Mid- Atlantic Ridge …alternating bands of high and low magnetism. Symmetrical bands on both sides. Why?

24. Magnetic anomalies also in volcanic lava.

25. Normal Reversed

26. Magnetic anomalies also in volcanic lava. Normal Reversed Earth’s magnetic field reverses direction. Layers “remember”. Older layers preserve their direction. Scientists constructed a magnetic time scale.

27. Gilbert reversed chron Gauss normal chron Matuyama reversed chron Brunhes normal chron 5.0 MaPresent4.03.02.01.0 Subchrons

28. Mid-ocean ridge 4.0 3.0 2.0 Ocean crust today Million years ago (Ma) 5.0 million years old 3.3 2.5 0.7 0 2.5 3.3 5.0

29. ASSEMBLY OF PANGAEA RODINIA Late Proterozoic, 750 Ma

30. ASSEMBLY OF PANGAEA RODINIA Late Proterozoic, 750 Ma Formed about 1.1 billion years ago; began to break up about 750 million years ago.

31. ASSEMBLY OF PANGAEA Late Proterozoic, 650 Ma

32. ASSEMBLY OF PANGAEA Late Proterozoic, 650 Ma The pre-Pangean pattern of continental drift.

33. ASSEMBLY OF PANGAEA Middle Ordovician, 458 Ma The pre-Pangean pattern of continental drift.

34. ASSEMBLY OF PANGAEA Early Devonian, 390 Ma The pre-Pangean pattern of continental drift.

35. ASSEMBLY OF PANGAEA PANGAEA (a) Early Triassic, 237 Ma

36. ASSEMBLY OF PANGAEA PANGAEA (a) Early Triassic, 237 Ma Assembled by 237 Ma.

37. BREAKUP OF PANGAEA (b) Early Jurassic, 195 Ma

38. BREAKUP OF PANGAEA (b) Early Jurassic, 195 Ma Signaled by the opening of rifts from which lava poured; relics can be found today in volcanic rocks from Nova Scotia to North Carolina.

39. BREAKUP OF PANGAEA (c) Late Jurassic, 152 Ma

40. BREAKUP OF PANGAEA (d) Late Cretaceous, Early Tertiary, 66 Ma

41. THE PRESENT-DAY AND FUTURE WORLD (e) PRESENT-DAY WORLD

42. THE PRESENT-DAY AND FUTURE WORLD (e) PRESENT-DAY WORLD The modern world has been produced over the past 65 million years.

43. THE PRESENT-DAY AND FUTURE WORLD (f) 50 million years in the future

44. Whole-mantle convection Upper mantle Lower mantle 700 km 2900 km Outer core Mantle Outer core Inner core

45. Whole-mantle convection Upper mantle Lower mantle 700 km 2900 km Outer core

46. Stratified convection Boundary near 700 km separates the two convection systems.