1. Plate Tectonics

2. Plate Tectonics explained by a 7 yr old…

3. The Claim… The Earth once had a single landmass that broke up into large pieces. This large continent is called Pangaea meaning” all Earth”. The Earth once had a single landmass that broke up into large pieces. This large continent is called Pangaea meaning” all Earth”.

4. Shoulder Partner How could you go about proving a theory like this? How do you convince people to support your ideas/thoughts? How could you go about proving a theory like this? How do you convince people to support your ideas/thoughts?

5. The Earth’s Drifting Continents Alfred Wegener was not the first to propose that the continents had been joined; however, he was the first to gather enough evidence.

6. Evidence from fossils… Glossopteris’ fossils (extinct plant) located in rocks about 250 million years old in South Africa, Australia, India and Antarctica. Seeds were too large to have been carried by wind and too fragile to have survived a trip by ocean waves.

7. Evidence from Rocks… An ancient folded mountain chain that stretches across S. Africa links up with an equally ancient folded mountain chain in Argentina.

8. The Evidence

9. Face Partner Can you think of any other type of evidence that Wegener could use?

10. The Real Issue……….. How could the continents move through the solid-rock bottoms of the oceans? In the 1950’s, scientists using better instruments found underwater mountain chains with rift valleys in their centers How could the continents move through the solid-rock bottoms of the oceans? In the 1950’s, scientists using better instruments found underwater mountain chains with rift valleys in their centers

11. Plate Interactions

12. Earth’s Spreading Ocean Floor Midocean ridges form the single largest mountain range in the world In between the ridges are thin cracks called transform faults. Midocean ridges form the single largest mountain range in the world In between the ridges are thin cracks called transform faults.

13. Midocean ridge

14. Mid-Ocean Ridges and an Ocean Floor Spreading

16. How do they prove that it’s really spreading? New deep-sea drilling machines showed the following evidence: A. rocks next to a mid-ocean ridge are younger than the rocks farther away. New deep-sea drilling machines showed the following evidence: A. rocks next to a mid-ocean ridge are younger than the rocks farther away. old  young young  old

17. B. Magnetic stripes on the ocean floor showed that the magnetic poles have reversed themselves nine times in the past 3.5 million years

18. Tectonic Plates

19. Without looking… What are the two things that prove that the ocean floor is spreading?

20. If the ocean floor is being created, is the Earth getting bigger? Ocean floor is being destroyed in trenches through subduction where oceanic crust slides under continental crust. The denser ocean crust is pushed downward into the mantle and melts Ocean floor is being destroyed in trenches through subduction where oceanic crust slides under continental crust. The denser ocean crust is pushed downward into the mantle and melts

21. Continental vs Oceanic Crust…

22. The Earth’s Moving Plates The Theory of Plate Tectonics links continental drift and seafloor spreading and helps to explain the formation, movement, collisions, and destruction of the Earth’s crust

23. Lithospheric Plates There are seven major plates (Pacific, North American, South American, Eurasian, African, Indo-Australian, and Antarctic) There are also 5 small plates. Each plate moves at a different speed and direction There are seven major plates (Pacific, North American, South American, Eurasian, African, Indo-Australian, and Antarctic) There are also 5 small plates. Each plate moves at a different speed and direction 3 cm N W per year

24. Plate Boundaries Divergent boundary- plates moving apart Volcanic islands and activity

25. Convergent boundary- plates that are moving together Mountain building, Earthquakes, Trenches, continental Volcanic activity

26. Transform boundary, slip-strike, lateral faults- plates slide past one another Earthquakes…and lots of them…sometimes severe!

27. Plate formation

28. Plate Motion The power of convection currents in the mantle is the force that moves the plates

29. TIME ELAPSED…

30. Table Talk How would plate boundaries act differently if ocean plates hit each other or if ocean plates hit continental plates? Would there be a difference? How would plate boundaries act differently if ocean plates hit each other or if ocean plates hit continental plates? Would there be a difference?

31. OCEAN TO OCEAN PLATES… The older oceanic plate is subducted and melted causing a string of volcanoes forming islands.

32. CONTINENTAL TO CONTINENTAL PLATES The continents fold upward to form large mountain ranges. Ex. Appalachian Mountains from when Africa collided with N. America.

33. Ocean to Continental The oceanic plate is subducted and a trench is formed. Can form mountains and volcanoes…

34. Plate Tectonics

35. PLATE TECTONICS…

36. Will the Earth Continue to Change?

37. The Earth’s Changing Surface Stress is what causes the surface of the Earth to change Put simply: It’s what plate boundary movements do to the land above. Stress is what causes the surface of the Earth to change Put simply: It’s what plate boundary movements do to the land above.

38. Types of Stresses Compression – (convergent) squeezes the rock Tension – (divergent) causes the rocks to stretch Shearing – (transformational) causes it to twist or tear Compression – (convergent) squeezes the rock Tension – (divergent) causes the rocks to stretch Shearing – (transformational) causes it to twist or tear

39. Faults Before StressShearing Tension Compression

40. Faulting Fault - A break or a crack in the earth’s crust where movement occurs. Footwall up Hanging Wall up

41. Faults Strike-Slip Fault Reverse Fault Normal Fault

42. Mountain Formation…

43. Folded Mountains When stress is applied to the rock and it bends but doesn’t break, folded mountains form. This process forms an anticline which is an upward fold and a syncline which is a downward fold When stress is applied to the rock and it bends but doesn’t break, folded mountains form. This process forms an anticline which is an upward fold and a syncline which is a downward fold

44. Anticline vs Syncline…

45. The “Floating” Crust Isostasy -the balance between the downward force of the crust and the upward force of the mantle

46. Tectonic Humor and we’re finally done!