Why does Earth have mountains? Where do they come from?

1. Why does Earth have mountains? • Where do they come from? • Why are there ocean fossils at the top of the Himalayas? • Why does California have Earthquakes? • Where do volcanoes come from?

2. Plate Tectonics Chapter 8

3. Alfred Wegener • Continental Drift • Wegener thought whole sections of the crust moved • Evidence • Shape of Continents • Rock Evidence • Same mountains on different continents • Fossil Evidence • Same fossils on different continents

4. Continental Drift Africa and South America look like they fit together • Click on the picture to see the evidence • Ancient Mountain Belts • Ancient Sand Dunes • Fossil Evidence

5. Continental Drift Fossil Evidence - Same fossils found on different continents • Mesosaurus • Lystrosaurus • Glossopteris • Cynognathus

6. Continental Drift • What the hypothesis was missing was the HOW? • Alfred Wegener proposed that the continents were moving on a more fluid layer under the crust that could possibly be moving due to internal heat . . . • He had no way to prove it!

7. He was right!. . .well mostly • He died before his hypothesis was accepted as a theory. • New technology allowed scientists to examine the structure of Earth • They found that the lithosphere was moving due to Earth’s internal heat. • This developed into the theory of Plate Tectonics

8. Who came up with continental drift? • Alfred Wegener • Sir Isaac Newton • Copernicus • Alfred Hitchcock

9. What evidence did Alfred Wegener use to support continental drift? • Shape of continents • Rock evidence • Fossil evidence • All of the above

10. Why could Alfred Wegener not prove continental drift? • He could not prove the land moved • He could not prove how the land moved • He did

11. Where do most earthquakes and volcanoes occur? • In the middle of plates • Along coasts • Along mountain ranges • Along plate boundaries

12. Plate Tectonics • Evidence • Continental Drift (continents fit, fossils, rocks) • New Evidence • Location of Earthquakes and Volcanoes (p173) • Magnetism of the ocean floor (p174) • Age of the ocean floor (p175)

13. Plate Tectonics Evidence Earthquakes and Volcanoes: • Most earthquake and volcano activity happen along plate boundaries. • Plates are moving apart, moving together, or sliding past one another. • This creates earthquakes • Where plates move apart and come together magma is brought to the surface • This creates volcanoes

14. Plate Tectonics World Earthquakes

15. See page 712 to view direction of plate movement

16. Plate Tectonics Evidence Magnetism of the Ocean Floor (see page 174) • Mid-ocean Ridges are places where NEW rock is forming. • These rocks contain magnetic minerals (minerals with iron) they point to the north pole • The north pole can flip with the south pole • These minerals flip too. This is called a magnetic reversal.

17. Plate Tectonics Seafloor Magnetism Video

18. Plate Tectonics Evidence • Age of the Ocean Floor • New rock is formed at a mid-ocean ridge or spreading center • These are formed in the middle of the ocean • The rock gets older as you move away from the ridge • The ocean floor is not that old because it subducts under continents • The oldest ocean floor is ~180 million years old

19. Plate Tectonics Age of the ocean floor

20. Earth’s Structure • Crust + Upper Mantle = Lithosphere (solid) • Asthenosphere “fluid” portion of the mantle • Mantle - Solid • Outer Core – Liquid • Inner Core – Solid • Heat comes from radioactive material in the core

21. Mantle Convection

22. Composition Thick Low Density High Silica Floats Thin High Density Low Silica Sinks

23. Divergent Convergent Transform 3 Types of Plate Boundaries:

24. Divergent Boundary Sea floor spreading • Large continents begin to crackand split apart • The gaps fill with water • Small seas become oceans • The mid ocean ridge continues to produce new crust

25. Divergent BoundaryCharacteristics • 2 plates are moving apart • Shallow Earthquakes • Magma comes to the surface and cools • Basalt rock forms • Dense and dark in color • Creates a Mid-Ocean Ridge • Rift valleys form in the center • Examples: Mid Atlantic Ridge and East Pacific Rise

26. Divergent BoundaryHow? • The plates are pulled apart by convection currents in the mantle below • Caused by heat released from natural radioactive processes • At mid-ocean ridges molten rock from below rises up to fill the gap with new basaltic rock

27. Let’s Draw a Divergent Boundary

28. Using the Map on page 712-713 Highlight the Divergent Boundaries

29. True or False: The magnetic polarity of Earth changes • True • False

30. Magnetic stripes of oceanic crust proves… • Earth is rotating • One piece of evidence to prove plate movement • That the rocks are very old

31. Seafloor rock gets older as… • You move away from the mid-ocean ridge • As you move toward the mid-ocean ridge • As you move into the mid-ocean ridge

32. The Lithosphere is… • The crust and the upper mantle • Another word for mantle • The crust and asthenosphere • The inner core

33. Which layers of the Earth are solid? • Inner Core • Outer Core • Mantle • Crust • All of the above • 1, 3, and 4

34. Which layers of the Earth are liquid? • Inner core • Outer core • Mantle • Asthenosphere • Crust • All of the above • 2 and 4

35. A divergent boundary is where plates… • Move apart • Come together • Slide past each other

36. All divergent boundaries eventually form… • Mountains • Oceans • Continents • The moon

37. Divergent Convergent Transform 3 Types of Plate Boundaries:

38. Convergent Boundaries • 2 plates are moving together • Ocean-Ocean • Ocean-Continent **Deep Earthquakes • Continent-Continent **Earthquakes Subduction Zone Volcanoes Form Creates Mountain Belts NO VOLCANOES

40. Convergent Boundaries-Subduction- • Ocean-Ocean or Ocean-Continent • The denser plate always subducts Volcano Forms • Subducting Plate • more dense Plate Melts

41. Ocean – Continent Subduction

42. Ocean – Continent Subduction • The ocean plate always subducts because it is more dense. • Continental volcanic arcs or a mountain chain of volcanoes form on the continental plate. • Examples: Cascades of N. America Andes of S. America

43. Ocean – Ocean Subduction

44. Ocean – Ocean Subduction • The denser ocean plate always subducts because it is more dense. • Volcanic island arcs or chains of volcanic islands form on the OTHER OCEAN plate. • Examples: Aleutian Islands, Alaska Mt Pinatubo, Philippines Mt Fuji, Japan

45. Lets Draw a Subduction Boundary

46. Collision Boundary

47. Collision Boundary

48. Convergence of India

49. Collision Boundary • There is NO SUBDUCTION because both plates are continental and have low density. • They buckle up forming mountains (not volcanoes) • Examples: Himalayas, India/Asia

50. Highlight and Label the Major Convergent Boundaries Using the Map on page 712-713 Highlight the Divergent Boundaries