Forces in Earth’s Crust (pages 162–168)

1. Forces in Earth’s Crust (pages 162–168)

2. Key QuestionsWhat happens to rocks when they are placed under the large forces created by plate movements?

3. Types of Stress (page 163)Key Concept: Tension, compression, and shearing work over millions of years to change the shape and volume of rock.

4. You should be able to… Explain how stress in the crust changes the earth’s surface. Describe where faults are usually found and why they form.

5. When Earth’s plates move, rocks are pushed and pulled. The pushing and pulling forces cause: stress.

6. Stress adds energy to rocks. Rocks keep storing the energy until they cannot stand any more stress. Then the rocks break or change shape.

7. Tension is stress that pulls and stretches rocks. Tension makes rocks thinner in the middle. Tension happens when two plates move apart.

8. Compression is stress that squeezes rocks. Compression makes rocks fold or break. Compression happens when two plates push together.

9. Shearing is stress that pushes rocks in opposite directions. Shearing makes rocks break, slip apart, or change shape. Shearing happens when two plates slip past each other in opposite directions.

10. Answer the following questions. ? ? ? ? ? ? ? ? ? ? ? ? ?

11. Circletheletterofthechoicethatdescribeshowstressaffectsrocks.Circletheletterofthechoicethatdescribeshowstressaffectsrocks. a. Stress adds energy to rocks. b. Stress uses up the energy in rocks. c. Stress squeezes energy out of rocks.

12. Pushes and pulls on rocks cause Stress that makes rocks fold or break is called stress compression

13. Stress that stretches rocks is called Stress that makes rocks break, slip apart, or change shape is called tension shearing

14. compression tension shearing

15. Kinds of Faults (pages 164–165)

16. Key Concept: Most faults occur along plate boundaries, where the forces of plate motion push or pull the crust so much that the crust breaks.

17. Students will be able to…Describe where faults are usually found and why they form.

18. There are three main types of faults: normal faults reverse faultsstrike-slip faults

19. A fault is a break in Earth’s crust where rocks are under stress.

20. In many faults, the fault line is slanted. So the block of rock on one side of the fault is above the block of rock on the other side of the fault.

21. The top block is called the hanging wall. The bottom block is called the footwall.

22. There are three different types of faults: normal faults reverse faultsstrike-slip faults Each type is caused by a different kind of stress on rocks.

23. A normal fault happens when tension pulls rocks apart. In a normal fault, the hanging wall slips down and becomes lower than the footwall.

24. A reverse fault happens when compression pushes rocks together. In a reverse fault, the hanging wall slides up and becomes higher than the footwall.

25. A strike-slip fault happens when shearing pushes rocks in opposite directions. In a strike-slip fault, two blocks of rock move past each other, but neither block moves up or down.

26. Answer the following questions ? ? ? ? ? ? ? ? ? ?

27. Circle the letter of the choice that explains what causes a fault. a. Stress increases on rocks until they move. b. Energy slowly drains away from rocks. c. Rocks heat up and melt.

28. tension Reverse fault Strike-slip fault

29. Reverse fault Normal fault Strike-slip fault c.

30. ChangingEarth’sSurface (pages166–168)

31. Key Concept:Over millions of years,the forces ofplatemovementcanchangeaflatplainintolandformssuch as anticlines and synclines,folded mountains,fault-block mountains,and plateaus.

32. Students will be able to…Identify the land features that result from plate movement.

33. Stresses in Earth’s crust cause the surface to change.Different stresses cause differentchanges.

34. Compressioncausesfolding.Foldingislikearuggettingwrinkled up when it is pushed across the floor.

35. Folds that bend upward into ridges are calledanticlines.Folds that bend downward into valleys arecalledsynclines.

36. Tension causes stretching.When crust stretches, many normalfaultsform.

37. Sometimes a block of rockmovesupwardbetweentwonormalfaults.The blockforms a mountain called afault-block mountain.

38. Stresses in the crust can also formplateaus.Aplateauis a large area of flat land that has been lifted up abovesea level.

39. Answer the following questions. ? ? ? ? ? ? ? ? ? ?

40. Circle the letter of the sentence that describes how a fault-block mountain forms. a. A block of rock moves upward between two normal faults. b. The crust becomes wrinkled like a rug. c. Rocks are pushed together by compression.

41. Is the following sentence true or false? A plateau forms when flat land is pushed up above sea level. TRUE