1. Alfred Wegener first proposed the theory of continental drift in 1912, suggesting that the continents were once joined together in a supercontinent called Pangaea before slowly drifting apart. 2. Wegener provided four lines of evidence to support his theory - similar rock formations and fossils on separated continents, matching coastlines, correlated climate indicators like coal deposits, and plant and animal distributions that could not have crossed oceans. 3. However, Wegener's theory was initially rejected because he could not explain what caused the continents to move. It was not until the 1950s-60s that seafloor spreading and plate tectonics were discovered, providing a mechanism to explain continental drift.

1. Plate Tectonics And Plate Boundaries HORRAH!!!

2. History of Plate Tectonics and Alfred Wegener

4. Abraham Ortelius’ Map

6. Gondwanaland

18. FINDING EVIDENCE The first way to map the ocean floor used Sonar. This way stunk because it didn’t accurately map the floor.

19. The then invented the Magnetometer. This could detect small changes in the magnetic field in rocks and map them.

21. Seafloor Spreading – new ocean crust is formed at ocean ridges and destroyed at deep sea trenches.

23. Convection current/Plate motion Plate motion is thought to be caused by convection currents in the asthenosphere. Since the hotter material deep in the asthenosphere is less dense it will slowly rise, as it reaches the base of the lithosphere it begins to cool, become more dense, and will sink. Rising convection currents will move plates apart (divergent), while sinking convection currents will move plates together (convergent). http://news.bbc.co.uk/nol/shared/spl/hi/pop_ups/04/world_how_volcanoes_erupt/img/1.jpg

24. Plate Boundaries and Convection Currents

26. These new maps showed the different magnetism in different layers of rock. As new crust is created the iron bearing minerals point to where the magnetic pole is at the time of creation. This is called Paleomagnetism

29. This proved that new sea floor was being created at mid-ocean ridges. Identical magnetism on opposite sides of ridges. Thus, the plates where moving.

30. Plate Boundaries and Convection Currents

31. Types of Boundaries

32. Divergent Boundaries two plates move apart

33. Ocean/Ocean Formations- ocean ridge, fissures

34. Mid-Atlantic Ridge it is 40,000 miles long

36. Mid-Ocean Ridge – Magnetic Reversals

37. Land/land Formations – rift valley

38. Great African Rift Valley

41. Convergent –two plates come together

42. Land/ocean Formations- subduction zone, trench, volcanoes, earthquakes

45. Mt St. Helens

48. Ring of Fire

49. Land/land Formations – Large Mountains (Orogeny)

52. Himalayas

55. Ocean/ocean Formations – island arc, trench

57. Eastern Caribbean

60. Transform – the plates slide past each other, they form faults

61. Friction builds up between the plates until they snap and cause EARTHQUAKES

62. San Andreas Fault

65. Hotspot

66. Hotspots The hotspot is also known as a magma chamber, it is located in the mantle

67. The Hotspot then explodes, creating a volcano

68. The plate then moves. Notice the volcano moves with the plate, but the hotspot stays were it was

69. The Hotspot then explodes again, forming a new volcano

70. The plate moves again, starting the process over

71. Another volcano is then created forming a Volcanic Chain

72. An example of a hotspot is Hawaii