Download Earth`s Crust in Motion

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Earth’s Crust in Motion
Earth’s Interior (page 314-322)
1. Why must scientists rely on indirect methods to observe Earth’s interior?
They can’t observe it directly.
2. True or false? The temperature changes as you go from the surface toward the center of Earth.
True
3. How does pressure change as you go from the surface toward the center of Earth?
Pressure increases
4. Label the layers of Earth by writing the name of the layer in the blank.
1. __ crust
______
2. ___ mantle
__
3. __ outer core ____
4. ___ inner core ___
5. The crust is a layer of rock that forms Earth’s outer skin.
6. The dark-colored rock that makes up most of the oceanic crust is basalt.
7. The light-colored rock that makes up most of the continental crust is granite.
8. Match the name of each layer of Earth with its description.
B mantle
a. rigid layer that includes the upper part of the mantle and crust
A lithosphere
b. layer of hot rock between the crust and the core
C asthenosphere
c. soft layer just below the lithosphere
9. True or false? The asthenosphere floats on the lithosphere.
False
Science 8- Earth’s Crust in Motion
Convection Currents and the Mantle (pages 323-325)
10. The movement of energy from a warmer object to a cooler object is called heat transfer.
11. The three types of heat transfer are radiation, convection and conduction.
12. Label each figure by writing the type of heat transfer it shows.
convection
conduction
radiation
13. What is radiation? What are two forms of radiation?
Heat transfer by electromagnetic waves.
Forms of radiation = heat you feel from the sun; heat you feel around a flame or open fire
14. What is conduction? What is an example of conduction?
Heat transfer by direct contact of particles of matter.
Examples of conduction = a spoon heating up if left in a cup of hot chocolate; your hand
burning when you touch a hot glass.
15. What is convection?
Heat transfer by the movement of a fluid.
16. Heat transfer by convection is caused by differences of temperature and density within a fluid.
17. A measure of how much mass there is in a volume of a substance is density.
18. Circle the letter of the sentence that describes what happens to a fluid when its temperature
increases.
a. Its particles occupy less space.
c. Its particles move more slowly.
b.Its density decreases.
d. Its particles settle together more closely.
Science 8- Earth’s Crust in Motion
19. Use arrows to show the convection currents that would flow if the pot of soup in the drawing were
heated.
If the statement is true, write true. If it is false, change the underlined word or words to make the
statement true.
radiation
20. False
The transfer of energy by electromagnetic waves is called convection.
21. True
Conduction is heat transfer by direct contact of particles of matter.
convection
22. False
Radiation is the transfer of heat by the movement of a heated fluid.
23. False
Density is a measure of how much heat there is in a volume of a substance.
mass
Core & upper part of
mantle
24. False
The heat source for the convection currents in the mantle is from the crust.
25. True
Convection currents flow in the asthenosphere.
26. True
The movement of energy from a warmer object to a cooler object is called heat
transfer.
Science 8- Earth’s Crust in Motion
Use the diagram to answer the following questions.
27. Where does the heat come from that drives this convection current in the mantle?
The heat that drives the convection current in the mantle comes from Earth’s core & from the
mantle itself
28. Where is the temperature of the mantle material greater, at point A or point C? Explain why.
The temperature of the mantle material is great at Point A because it is closer to the heat
source and just beginning to rise where Point C is at the top and is just starting to fall.
29. Where is the density of the material greater, at point A or point C? Explain why.
The density is greater at Point C because the convection current slowly cools off and the
cooler material is denser than hot material.
30. What causes the convection cell to turn to the left at point B?
The convection cell turns to the left at Point B because the rising material hits the lithosphere
and cannot go up any more.
31. What happens to the temperature and density of the material between points B and C?
The material continues to cool down so the temperature drops between Point B & C. As the
temperature drops, the density increases.
32. What force causes the convection cell to turn down at point C?
Gravity
33. What happens to the temperature and density of the material between points D and A?
The heat from the core causes the temperature of the material to rise.
As the temperature rises, the density decreases.
Science 8- Earth’s Crust in Motion
34. What causes the convection cell to turn up at point A?
The density of the material at Point A is less than the material above it, so it begins to rise.
35. How do you think this convection cell might affect the crust material above it?
Several answer possibilities: The movement of the mantle material will cause some movement in
the crust material.
Drifting Continents (pages 326–330)
36. State Alfred Wegener’s hypothesis about how Earth’s continents have moved.
Wegener’s hypothesis was that all the continents had once been joined together in a single
landmass and have since drifted apart, to their current locations.
37. Wegener named his supercontinent Pangaea.
38. What did Wegener think had happened to this supercontinent?
Wegener thought that this supercontinent had broken apart and that the pieces had slowly
moved to become the continents as they are today
39. Wegener’s idea that the continents slowly moved over Earth’s surface became known as continental
drift.
40. Continental drift is supported by evidence from landforms/puzzle pieces, fossils and climate.
41. How do the locations of mountains support Wegener’s idea about how mountains form?
Mountains usually occur in narrow bands along the edges of continents, as you would expect
if the collision of continents forms mountains.
Sea-Floor Spreading (pages 331–337)
42. The process that continually adds new material to the ocean floor is called sea-floor spreading.
43. Deep underwater canyons are called deep ocean trenches.
44. What is subduction?
The process by which the ocean floor sinks beneath a deep-ocean trench.
45. Why is the Atlantic Ocean expanding?
The Atlantic Ocean is expanding because it has only a few short deep-ocean trenches, and
the spreading ocean floor has virtually nowhere to go.
Science 8- Earth’s Crust in Motion
46. Name and describe the feature of the ocean floor shown at A.
A is the mid-ocean ridge. A mountain chain that extends along the sea floor into all of Earth’s
oceans.
47. Describe the process shown occurring at B, and explain what results from this.
Point B is sea-floor spreading. It continually adds new material to the ocean floor.
48. What happens to old oceanic crust as new molten material rises from the mantle?
The new material splits apart the old material and pushes it aside.
49. The arrows on the figure show the ocean floor spreading from the ridge. What are three kinds of
evidence scientists have found to support this idea?
1. evidence from molten material
2. evidence from magnetic stripes
3. evidence from drilling samples
50. What process is shown occurring at C, and why does it occur?
 Subduction at a deep-ocean trench is occurring at C.
 It occurs because oceanic crust becomes denser as it moves farther away from the midocean ridge. Gravity pulls the dense oceanic crust down beneath the trench.
The Theory of Plate Tectonics (page 340–345)
51. The lithosphere is broken into separate sections called plates.
52. What is the theory of plate tectonics?
Pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in
the mantle
53. The plates of the lithosphere float on top of the asthenosphere.
Science 8- Earth’s Crust in Motion
54. Complete the table.
55. Most divergent boundaries occur at the mid-ocean ridge.
56. When two plates converge, the result is called a(n) collision.
57. When two plates collide, what determines which plate comes out on top?
The density of the plates determines which plate comes out on top. The less dense plate is on
top.
58. About how fast do plates move?
about one to ten centimeters per year.
59. Label each figure by writing the type of plate boundary it shows.
Divergent
Convergent
Transform
60. Describe what happens when two plates carrying continental crust collide
The denser plate subducts below the other plate at a deep-ocean trench.
61. Describe what happens when a plate carrying oceanic crust collides with a plate carrying continental
crust.
The collision squeezes the crust into mountain ranges
Science 8- Earth’s Crust in Motion
Changing Earth’s Surface (pages 346–353)
62. What is a fault? Where do faults usually occur?
A fault is a break in Earth’s crust where slabs of crust slip past each other.
Faults usually occur along plate boundaries, where the forces of plate motion compress, pull, or
shear the crust so much that the crust breaks.
63. Mountain building is the result of folding & faulting and is driven by plate movement.
64. What is the Ring of Fire?
The Ring of Fire is a volcanic belt formed by the many volcanoes that rim the Pacific Ocean.
65. Why do volcanic belts form along the boundaries of Earth’s plates?
The lithosphere is weak and fractured along the boundaries, allowing magma to reach the
surface.
66. What is a hot spot?
A hot spot is an area where magma from deep within the mantle melts through the crust like a
blowtorch through steel
67. Where is there a hot spot under the North American Plate?
Yellowstone National Park in Wyoming
Science 8- Earth’s Crust in Motion