Chapter Menu

1. Chapter Introduction Lesson 1 Forces That Shape Earth Lesson 2 Landforms at Plate Boundaries Lesson 3Mountain Building Lesson 4 Continent Building Chapter Wrap-Up Chapter Menu

2. How is Earth’s surface shaped by plate motion? Chapter Introduction

3. What do you think? Before you begin, decide if you agree or disagree with each of these statements. As you view this presentation, see if you change your mind about any of the statements. Chapter Introduction

4. 1. Forces created by plate motion are small and do not deform or break rocks. 2. Plate motion causes only horizontal motion of continents. 3. New landforms are created only at plate boundaries. Do you agree or disagree? Chapter Introduction

5. 4.The tallest and deepest landforms are created at plate boundaries. 5. Metamorphic rocks formed deep below Earth’s surface sometimes can be located near the tops of mountains. 6. Mountain ranges can form over long periods of time through repeated collisions between plates. Do you agree or disagree? Chapter Introduction

6. 7. The centers of continents are flat and old. 8. Continents are continually shrinking because of erosion. Do you agree or disagree? Chapter Introduction

7. Forces That Shape Earth • How do continents move? • What forces can change rocks? • How does plate motion affect the rock cycle? Lesson 1 Reading Guide - KC

8. Forces That Shape Earth • isostasy • subsidence • uplift • compression • tension • shear • strain Lesson 1 Reading Guide - Vocab

9. Plate Motion • Mountain ranges are produced by plate tectonics. • The theory of plate tectonics states that Earth’s surface is broken into rigid plates that move horizontally on Earth’s more fluid upper mantle. • Mountains and valleys form where plates move away from each other or slide past each other. Lesson 1-1

10. Vertical Motion Isostasy is the equilibrium between continental crust and the denser mantle below it. isostasy from Greek iso, means “equal”; and Greek stasy, means “standing” Lesson 1-2

11. You need to understand forces that act on Earth’s plates to understand how they can rise to form mountains. • A continent floats on top of the mantle because the mass of the continent is equal to the mass of the mantle it displaces. • This is also why icebergs float on the surface water.

12. Vertical Motion(cont.) • Plates formed of continental crust are less dense than the fluid rock that forms the mantle, and part of the continental crust floats above the surface of the mantle. • The continental crust displaces some of the mantle below it until an equilibrium is reached, which is called isostasy. Lesson 1-2

13. The crust will sink and rise as its mass changes, in order to reach equilibrium. If a part of the continental crust becomes thicker, it sinks deeper into the mantle. The crust can also rise higher if it becomes lighter. • The mantle will push up on the thicker crust until a balance is reached.

14. Weathering and erosion remove the top part of a mountain. After this happens, the crust rises to maintain isostasy. • The mountain stops moving when the mass of the mountain equals the mass of the mantle it displaces.

15. Vertical Motion(cont.) • Much of North America was covered by glaciers more than 1 km thick 20,000 years ago. • The weight of the ice pushed the crust downward into the mantle in a process called subsidence. Lesson 1-2

16. The downward vertical motion of Earth’s surface is called subsidence.

17. When the ice melted and the water ran off, the isostatic balance was upset. In response, the crust moved upward in a process called uplift. • The upward vertical motion of Earth’s surface is called uplift.

18. Vertical Motion(cont.) What can cause Earth’s surface to move up or down? Lesson 1-2

19. Horizontal Motion • Horizontal motion at plate boundaries applies much greater forces to rocks than vertical motion does. • Forces at plate boundaries are strong enough to break rocks or change the shape of rocks. Lesson 1-3

20. Horizontal Motion(cont.) • Stress is the force acting on a surface. • Squeezing stress is compression. • Stress that pulls something apart is tension. • Parallel forces acting in opposite directions are shear. Lesson 1-3

21. Compression, tension, and shear can all cause rocks to change shape. Lesson 1-3

22. Horizontal Motion(cont.) • A change in the shape of rock caused by stress is called strain. • Elastic strain does not permanently change, or deform, rocks. It occurs when stresses are small or rocks are very strong. • Plastic strain creates a permanent change in shape. Lesson 1-3

23. Horizontal Motion(cont.) plastic Science Use capable of being molded Common Use a commonly used synthetic material Lesson 1-3

24. Horizontal Motion(cont.) • Compression thickens and folds layers of rock. • Tension stretches and thins layers of rock. Lesson 1-3

25. Horizontal Motion(cont.) • In the upper crust, the rocks are cold, and forces cause the rocks here to break rather than to change shapte. • When strain breaks rocks rather than just changing their shape, it is called failure. • When rocks fail, fractures—or faults—form. Lesson 1-3

26. Horizontal Motion(cont.) What causes rocks to thicken or fold? Lesson 1-3

27. Plate Tectonics and the Rock Cycle • Rocks are always moving through the rock cycle, both vertically and horizontally. • The theory of plate tectonics combined with uplift and subsidence explain why there is a rock cycle on Earth. • The forces that cause plate tectonics produce horizontal motion. • Isostasy results in vertical motion within continents. Lesson 1-4

28. Uplift brings metamorphic and igneous rock from deep in the crust up to the surface, where erosion breaks down rocks into sediment. • Buried sediment becomes sedimentary rocks, which with pressure and temperature eventually become metamorphic rocks. • Subduction takes all types of rocks deep into Earth, where they can melt and become new igneous or metamorphic rocks.

29. Horizontal tectonic motion and vertical motion by uplift and subsidence help move rocks through the rock cycle. Lesson 1-4

30. Plate Tectonics and the Rock Cycle (cont.) How does plate motion affect the rock cycle? Lesson 1-4

31. As a mountain is eroded away, the continent will rise until isostatic balance is restored. • Different types of stress change rocks in different ways. Lesson 1 - VS

32. Horizontal and vertical motions are part of what keep rocks moving through the rock cycle. Lesson 1 - VS

33. What term refers to the equilibrium between continental crust and the denser mantle below it? A. uplift B. subsidence C. isostasy D. compression Lesson 1 – LR1

34. Which term refers to a change in the shape of rock caused by stress? A. tension B. strain C. compression D. shear Lesson 1 – LR2

35. What is the downward vertical motion of Earth’s surface called? A. subsidence B. uplift C. isostasy D. none of the above Lesson 1 – LR3

36. 1. Forces created by plate motion are small and do not deform or break rocks. 2. Plate motion causes only horizontal motion of continents. Do you agree or disagree? Lesson 1 - Now

37. Landforms at Plate Boundaries • What features form where two plates converge? • What features form where two plates diverge? • What features form where two plates slide past each other? Lesson 2 Reading Guide - KC

38. Landforms at Plate Boundaries • ocean trench • volcanic arc • transform fault • fault zone Lesson 2 Reading Guide - Vocab

39. Landforms Created by Plate Motion • Massive, slow-moving tectonic plates have so much force they can build tall mountains, form deep valleys, and rip Earth’s surface apart. • Compression, tension, and shear stresses each produce a different type of landform. Lesson 2-1

40. Landforms Created by Compression • The largest landforms on Earth are produced by compression at convergent plate boundaries. • A collision between two continental plates can produce tall mountains that form slowly and in stages over millions of years. • Although plates move horizontally, the collision cause the crust to move vertically as well. Lesson 2-2

41. The plates beneath India and Asia started colliding almost 50 million years ago. Because the plates are still colliding, the Himalayas grow a few millimeters each year due to compression. Lesson 2-2

42. Landforms Created by Compression (cont.) • When two plates collide, one can go under the other and be forced into the mantle in a process called subduction. • A deep trench forms where the two plates meet. • Ocean trenches are deep, underwater troughs created by one plate subducting under another plate at a convergent plate boundary. Lesson 2-2

43. Landforms Created by Compression (cont.) What two landforms can form where two plates converge? Lesson 2-2

44. Landforms Created by Compression (cont.) • Volcanic mountains can form in the ocean where plates converge and one plate subducts under another one. • The volcanoes form islands about 100 km in distance from where the two plates meet. • The curved line of volcanic islands that forms parallel to a plate boundary is called a volcanic arc. Lesson 2-2

45. Volcanic arcs can also form on continents. Lesson 2-3

46. Landforms Created by Tension A long, tall mountain range that forms where oceanic plates diverge is called a mid-ocean ridge. Lesson 2-3

47. Where plates move apart, tension stresses stretch Earth’s crust. • At divergent boundaries, oceanic plates, move apart, and there are tension stresses that cause crust to spread apart. • As tension stresses cause oceanic crust to spread apart, hot rock from the mantle rises.

48. The hot mantle rise and pushes the seafloor upward, making a long, tall ridge on the bottom of the ocean, called a mid-ocean ridge.

49. Landforms Created by Tension(cont.) When divergent boundaries occur within a continent, they can form continental rifts, or enormous splits in Earth’s crust. Lesson 2-3

50. Tension stresses in the cold upper part of the crust create faults. • At these faults, large block of crust move downward, creating a rift valley between two ridges.