1. Chapter 17- Plate Tectonics
8th Grade Science
Chapter 17- Plate Tectonics
© Fall 2005, Pflugerville ISD, 8th Grade

2. Chapter 17- Plate Tectonics
Section 1: Restless Continents
Section 2: The Theory of Plate Tectonics
Section 3: Deforming the Earth’s Crust
Unit 4 : Chapter 17 : Section 1

3. Do the Continents Move? What Do You Think?
Explain why the following statement is true or false:
The state of Texas is moving to the west
Unit 4 : Chapter 17 : Section 1

4. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
As the ocean floor spreads, Europe moves east and North America moves west
Unit 4 : Chapter 17 : Section 1

5. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The earth is layered like a chocolate-covered cherry
Unit 4 : Chapter 17 : Section 1

6. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The layers have different properties and different compositions
Unit 4 : Chapter 17 : Section 1

7. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The lithosphere is the cool, outermost layer of the Earth
Unit 4 : Chapter 17 : Section 1

8. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
It is divided into huge pieces called tectonic plates, which move on the asthenosphere
Unit 4 : Chapter 17 : Section 1

9. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Asthenosphere is the solid, soft layer of the mantle below the lithosphere
Unit 4 : Chapter 17 : Section 1

10. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Asthenosphere is made of mantle rock that flows slowly, allowing tectonic plates to move on it
Unit 4 : Chapter 17 : Section 1

11. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The mesosphere is the solid lower part of the mantle below the asthenosphere
Unit 4 : Chapter 17 : Section 1

12. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The outer core is the outer shell of Earth’s core. It is made of liquid iron and nickel
Unit 4 : Chapter 17 : Section 1

13. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The inner core is a sphere of solid iron and nickel
Unit 4 : Chapter 17 : Section 1

14. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The core is the solid cherry surrounded by gooey mantle covered with a thin chocolate crust
Unit 4 : Chapter 17 : Section 1

15. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Alfred Wegener, a German scientist, first had the idea that continents can drift around the globe
Alfred Wegener
Unit 4 : Chapter 17 : Section 1

16. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Wegener’s theory of continental drift explained why some land masses fit like puzzle pieces
Unit 4 : Chapter 17 : Section 1

17. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Continental drift also explained why similar fossils are found separated by the oceans
Unit 4 : Chapter 17 : Section 1

18. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Wegener’s theory had the continents plowing through the oceans like this ship plows through ice
Unit 4 : Chapter 17 : Section 1

19. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
As is usual with new theories, most scientists didn’t believe in continental drift
Unit 4 : Chapter 17 : Section 1

20. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
In the late 1960s, this ship was designed to drill into the ocean floor for core samples
Glomar Challenger
Unit 4 : Chapter 17 : Section 1

21. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The core samples revealed that rock at the center of the Atlantic (Red) was younger than rock at the edges (Blue)
Unit 4 : Chapter 17 : Section 1

22. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
The process by which new oceanic crust forms at mid-ocean ridges was called seafloor spreading
Unit 4 : Chapter 17 : Section 1

23. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Scientists later discovered that the earth’s magnetic field changes polarity every few thousand years
Unit 4 : Chapter 17 : Section 1

24. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
As the rock cools, it records these magnetic reversals in the seafloor
Unit 4 : Chapter 17 : Section 1

25. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
With continental fit, seafloor spreading, and magnetic reversals as proof, Wegener’s theory was proved!
Alfred Wegener
Unit 4 : Chapter 17 : Section 1

26. Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
With this new theory of Plate Tectonics, Wegener’s idea of a supercontinent was accepted
Unit 4 : Chapter 17 : Section 1

27. The Theory of Plate Tectonics
What Do You Think?
Consider the amount of energy it would take for humans to pick up a public school and move it a mile. What forces do you think cause the movement of the continents?
Unit 4 : Chapter 17 : Section 2

28. The Theory of Plate Tectonics
Unit 4 : Chapter 17 : Section 2

29. The Theory of Plate Tectonics
Unit 4 : Chapter 17 : Section 2

30. The Theory of Plate Tectonics
Unit 4 : Chapter 17 : Section 2

31. The Theory of Plate Tectonics
Unit 4 : Chapter 17 : Section 2

32. Tectonic Plate Boundaries
Where the plates meet, three types of plate boundaries can form…
Unit 4 : Chapter 17 : Section 2

33. Tectonic Plate Boundaries
A convergent boundary is where two tectonic plates collide, or run into each other
Convergent Boundary
Unit 4 : Chapter 17 : Section 2

34. Convergent Boundaries
Unit 4 : Chapter 17 : Section 2

35. Convergent Boundaries
Unit 4 : Chapter 17 : Section 2

36. Convergent Boundaries
Unit 4 : Chapter 17 : Section 2

37. Tectonic Plate Boundaries
A divergent boundary is where two tectonic plates separate from each other
Divergent Boundary
Unit 4 : Chapter 17 : Section 2

38. Unit 4 : Chapter 17 : Section 2
Divergent Boundary
Unit 4 : Chapter 17 : Section 2

39. Tectonic Plate Boundaries
A transform boundary is where two tectonic plates slide past one another horizontally
Transform Boundary
Unit 4 : Chapter 17 : Section 2

40. Unit 4 : Chapter 17 : Section 2
Transform Boundary
Unit 4 : Chapter 17 : Section 2

41. Unit 4 : Chapter 17 : Section 2
Tectonic Settings
Scientists use plate tectonics to explain how landforms like mountains and ocean basins form
Unit 4 : Chapter 17 : Section 2

42. Unit 4 : Chapter 17 : Section 2
Tectonic Settings
Unit 4 : Chapter 17 : Section 2

43. Unit 4 : Chapter 17 : Section 2
Tectonic Settings
Unit 4 : Chapter 17 : Section 2

44. Unit 4 : Chapter 17 : Section 2
Tectonic Settings
Unit 4 : Chapter 17 : Section 2

45. Unit 4 : Chapter 17 : Section 2
Tectonic Settings
Unit 4 : Chapter 17 : Section 2

46. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
What Do You Think?
The Indian Ocean tsunami of 2004 originated at a subduction zone. How did plate tectonics cause these waves that killed over 100,000 people?
Unit 4 : Chapter 17 : Section 3

47. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
Unit 4 : Chapter 17 : Section 3

48. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
Unit 4 : Chapter 17 : Section 3

49. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
Stress is the amount of force per unit area that is put on a rock
Unit 4 : Chapter 17 : Section 3

50. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
Strain is any change in a rock’s shape caused by stress
Unit 4 : Chapter 17 : Section 3

51. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
The deformed strata have been strained by the stress of compression
Unit 4 : Chapter 17 : Section 3

52. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
Folding is a type of strain that occurs when rocks bend
Unit 4 : Chapter 17 : Section 3

53. Unit 4 : Chapter 17 : Section 3
Deforming the Crust
Faulting is a type of strain that occurs when rock breaks
Unit 4 : Chapter 17 : Section 3

54. Unit 4 : Chapter 17 : Section 3
Building Mountains
Almost all mountains are formed at tectonic plate boundaries
Mt. Everest, Himalayas
Unit 4 : Chapter 17 : Section 3

55. Building Mountains- Divergent
The mid-ocean ridge system is made of two types of mountains:
Unit 4 : Chapter 17 : Section 3

56. Building Mountains- Divergent
Fault-block mountains form where the crust is rifting, or separating
Unit 4 : Chapter 17 : Section 3

57. Building Mountains- Divergent
Volcanic mountains form outside of the Rift Zone, on either side
Unit 4 : Chapter 17 : Section 3

58. Building Mountains- Convergent
At convergent boundaries, either volcanic or folded mountains can form
Convergent Boundary
Unit 4 : Chapter 17 : Section 2

59. Building Mountains- Convergent
In Alaska, the subduction of the oceanic Pacific plate has created a chain of volcanoes
Unit 4 : Chapter 17 : Section 3

60. Building Mountains- Convergent
When ocean was between India and Asia, there were volcanoes
Unit 4 : Chapter 17 : Section 3

61. Building Mountains- Convergent
As the continents collide, they create only folded mountains
Unit 4 : Chapter 17 : Section 3

62. Building Mountains- Convergent
The Nazca Plate is being subducted beneath the SA Plate
Unit 4 : Chapter 17 : Section 3

63. Building Mountains- Convergent
The result is a trench in the ocean and a chain of volcanoes on the continent
Unit 4 : Chapter 17 : Section 3

64. Describe Alfred Wegener’s theory of continental drift.
Let’s Review!
- 1 -
Describe Alfred Wegener’s theory of continental drift.
How is this different from the modern theory of plate tectonics?
Unit 4 : Chapter 17 : Section 1

65. What are the three possible driving forces of plate tectonics?
Let’s Review!
- 2 -
What are the three possible driving forces of plate tectonics?
Unit 4 : Chapter 17 : Section 2

66. What kind of mountains would you expect to find near an ocean trench?
Let’s Review!
- 3 -
What kind of mountains would you expect to find near an ocean trench?
Unit 4 : Chapter 17 : Section 3

67. What kinds of mountains would you expect to find at a mid-ocean ridge?
Let’s Review!
- 4 -
What kinds of mountains would you expect to find at a mid-ocean ridge?
Unit 4 : Chapter 17 : Section 3

68. Web Sites to Visit:
Unit 4 : Chapter 17

69. Unit 4 : Chapter 17 : Section 1
Pre-AP Extensions
Unit 4 : Chapter 17 : Section 1