Download Skinner Chapter 4

Fall 2000
Lohrengel
Geology 1013 - Earth System Science
Chapter 4 - Study
Instructions:
Read each question carefully before answering. Work at a steady pace, and you should
have ample time to finish.
_____________________________________________
1. Rocks deep inside the Earth are so hot that it is possible for them
to flow like sticky liquids.
2. Radiation is the process by which heat is transferred through solid
rock, or any other solid body, without changing the shape of the
solid.
3. The process of flow in solid materials is not directly observable,
because it only occurs deep within the Earth.
4. Conduction is the most important process by which heat is
transferred from the Earth's interior to its surface.
5. Volcanic eruptions are unrelated to the output of energy from the
Sun.
6. Iron-bearing minerals lose their magnetism above the Curie point.
7. Paleomagnetis m is a property of rocks, which records the directions
of ancient magnetic fields at the time of rock formation.
8. Sedimentary rocks cannot acquire magnetism, only rocks crystallized
from a magma can become permanently magnetized.
9. The Sierra Nevada of California is an example of an ancient magmatic
arc, evidence that the western margin of North America was once a
subduction zone.
10. Continental crust is thicker than oceanic crust.
11. The surface expression of convection inside the Earth is
a. the growth of mountains.
b. continental drift.
c. plate tectonics.
d. the formation of new oceans.
e. All of these are true.
12. Plate tectonics is
a. the slow lateral movement of segments of the Earth's hard,
outermost shell as a result of conduction currents deep inside
the Earth.
b. the slow lateral movement of segments of the Earth's hard,
outermost shell as a result of convection currents deep inside
the Earth.
c. the principal mechanism of heat transfer from the inside of the
Earth.
d. caused by the transfer of part of the Earth's rotational energy
to the Earth's surface, in the form of tides.
13. The Himalayan mountains represent a modern example of a
a. continent-continent collisional plate boundary.
b. continent-ocean collisional plate boundary.
c. subduction zone collisional plate boundary.
d. transform plate boundary.
14. Which one of the following does not belong with the others?
a. subduction
b. convergent margin
c. island arc
d. spreading center
15. Which one of the following statements is false?
a. The minerals in lava crystallize at temperatures well above the
Curie point of magnetite.
b. As the crystallized lava cools, the temperature drops below the
Curie point.
c. When the temperature of magnetite drops below its Curie point,
the magnetite loses its permanent magnetism.
d. The grains of magnetite in a solidified lava will carry a record
of the Earth's magnetic field at the moment the lava cooled below
the Curie point.
16. The "plates" referred to in the theory of plate tectonics are
a. relatively thin slabs of rigid rock floating on the mantle.
b. defined by their relative thickness.
c. formed around the major continents.
d. distinguished from one another by their relative densities.
17. Midocean ridges define
a. convergent plate boundaries.
b. shear plate boundaries.
c. divergent plate boundaries.
d. All of these are true.
18. Which one of the following does not belong with the others?
a. divergent margin
b. back-arc basin
c. midocean ridge
d. seafloor spreading
19. Alfred Wegener
a. was the first to propose the hypothesis of continental drift.
b. amassed an impressive body of evidence in support of the
hypothesis of continental drift.
c. used paleomagnetism to prove the hypothesis of seafloor spreading
and continental drift.
d. All of these are true.
20. The San Andreas Fault is a(n) _____________ that marks the boundary
between the Pacific and North American plates.
a. collision zone
b. transform fault
c. subduction zone
d. island arc
21. The Earth's magnetic field is caused by
a. the rotation of the planet.
b. flow of molten iron in the outer core.
c. electrical currents in the outer core.
d. All of these are true.
22. Reversals of the Earth's magnetic poles
a. are not very well understood.
b. provided evidence, through paleomagnetism, for seafloor
spreading.
c. are recorded in the permanent magnetism of lavas millions of
years old.
d. All of these are true.
23. The number of large lithospheric plates is
a. ten.
b. six.
c. about twenty.
d. too many to count.
24. We can determine absolute plate motion by reference to
a. other plates.
b. hot spots.
c. the positions of volcanoes in the Earth's crust.
d. midocean ridges.
25. Convergent ma rgins
a. occur where two plates are moving toward each other.
b. are characterized by the formation of midocean ridges.
c. involve the formation of new continental crust.
d. All of these are true.
26. A linear zone along which a plate of lithosphere sinks down into the
asthenosphere is called a(n)
a. subduction zone.
b. magmatic arc.
c. island arc.
d. continental slope.
27. A collision zone marks
a. the disappearance of an ocean.
b. the convergence of two plates capped by continental crust.
c. the tectonic setting in which spectacular mountain ranges are
uplifted.
d. All of these are true.
28. The increase in temperature with increasing depth in the Earth is
called
a. convection.
b. the geothermal gradient.
c. plate tectonics.
d. isostasy.
29. Paleomagnetic evidence of seafloor spreading provided crucial
support for the theory of plate tectonics, because it showed, once
and for all, that
a. new oceanic crust is created along midocean ridges.
b. continents move with respect to ocean basins.
c. the Earth's magnetic field reverses every few million years.
d. All of these are true.
30. The answer is "Benioff zone." What is the question?
a. What do scient ists call the area of local crustal thickening in
front of a fore-arc ridge?
b. What do scientists call the zone where a divergent plate boundary
first begins to split apart?
c. What do scientists call the portion of the mantle that is of such
high temperature that convection can occur, even though the
material is solid?
d. What do scientists call a zone of deep-seated earthquakes,
generated by the downward movement of a cold slab of lithosphere
in a subduction zone?
31. There are three main mechanisms of heat transfer: ______________,
________________, and _______________.
32. The increase in temperature with depth inside the Earth is called
the ________________.
33. The hypothesis that new oceanic crust is created at midocean ridges
by magma rising from deep inside the Earth is called ______________.
34. Divergent margins are also called ___________________.
35. The two main types of convergent margins are __________________ and
__________________.
36. The deepest parts of the ocean are the ________________ associated
with subduction zones.
37. The San Andreas Fault is an example of a(n) _______________ type of
plate boundary.
38. The fastest- moving plates are the Pacific and Nazca plates, which
move at a speed of about _________________.
39. A chain of volcanic islands that forms above a subduction zone is
called a(n) _________________.
40. The temperature above which a magnetic material loses its permanent
magnetism is called its __________________.
41. What is the source of the Earth's magnetism?
42. What is a Benioff Zone?
43. Draw neat, well- labelled diagrams to illustrate the difference
between a convergent margin where subduction is occurring and a
convergent margin where continental collision is occurring.
44. What is the source of the energy that drives plate motion?
45. What is a hot spot?
46. Why was Wegener's hypothesis of continental drift not widely
accepted when it was first proposed?
47. Sketch and neatly label a box diagram of the rock cycle.
48. With reference to Figure 4.17 from the text, describe the
characteristics of the earthquakes that are commonly associated with
each type of plate margin.
49. What are the main differences between oceanic crust and continental
crust?
50. What is the difference between the continental shelf, the
continental slope, and the continental rise? Where does the edge of
a continent lie?
51. How did paleomagnetic evidence lead to the acceptance of the
hypothesis of seafloor spreading?
52. Describe how hotspots and satellite data can help scientists study
plate motion.
53. Describe the main types of plate margins.
54. Describe the process whereby a continental rift can evolve into a
new ocean.
55. Discuss the mechanisms proposed to explain the movement of the
lithosphere in plate tectonics.
56. What is the difference between absolute motion and relative motion,
and why is this difference relevant to the study of lithospheric
plates?
57. Describe the major topographic features of the ocean floor, and
place them in the context of plate tectonic theory.
58. What is apparent polar wandering, and how did its discovery lend
support to the hypothesis of continental drift?
_____________________________________________
Fall 2000
Lohrengel
Geology 1013 - Earth System Science
Answer Key: Chapter 4 - Study
1. T
2. F
3. F
4. T
5. T
6. T
7. T
8. F
9. T
10. T
11. E
12. B
13. A
14. D
15. C
16. A
17. C
18. B
19. B
20. B
21. D
22. D
23. B
24. B
25. A
26. A
27. D
28. B
29. A
30. D
31. radiation...conduction...convection
32. geothermal gradient
33. seafloor spreading
34. (spreading centers) OR (rifts)
35. subduction zones...collision margins or collision zones
36. trenches
37. (transform) OR (transform fault)
38. (9 cm/yr) OR (3.5 in/yr)
39. (island arc) OR (magmatic arc)
40. Curie point
41. The source of the Earth's magnetism is the outer core, which is
molten.
42. A Benioff Zone is a region inside the Earth where very deep focus
earthquakes occur. These slanting zones are the places where old
lithosphere is sinking into the asthenosphere. [See Fig. 4.14 in the
text.]
43. [See Fig. 4.17 in the text.]
44. The Earth's internal energy drives plate motion. (or) Convection in
the mantle drives plate motion.
45. A hot spot is a long- lived magma source deep within the mantle.
Sometimes they cause intraplate volcanism, as in the Hawaiian chain
of volcanic islands. The lithosphere appears to move over hot spots,
because they are so deep-seated, so they can be used as reference
points in studying the absolute motion of plates.
46. In spite of the impressive evidence presented by Wegener in favor of
continental drift, the hypothesis was not widely accepted because no
one could explain how a solid, rocky continent could possibly
overcome friction and slide across the oceanic crust.
47. [See Fig. 4.27 in the text.]
48. [Provide students with a copy of Fig. 4.17 from the text, with no
caption.]
A. Divergent margin: earthquakes are shallow and weak.
B. Convergent margin with subduction: earthquakes are deepƒƒdown to
700 kmƒƒand very strong.
C. Convergent margin with collision: earthquakes down to 300 km and
sometimes strong.
D. Transform fault margin: earthquakes down to 100 km and often
strong.
49. Continental crust is much thicker, "floats" higher on the
lithosphere (i.e., topographically higher), and much lower in
density (ave. density 2.7 gm/cm 3 compared to 3.2 gm/cm 3 for
oceanic crust). [There is also a compositional difference, not
discussed in this chapter of the text.]
50. A continental shelf is the flooded margin of the continent itself.
The geological edge of the ocean basin is not the shoreline; rather,
it is the place where oceanic crust joins continental crust. The
geological edge of an ocean basin is at the bottom of the
continental slope, a pronounced slope beyond the seaward margin of
the continental shelf. The continental rise is a gentle slope at the
base of the continental slope, leading to the ocean floor. The true
edge of the continentƒƒwhere oceanic crust meets continental
crustƒƒis usually submerged in water and often covered by sediment.
51. * not available *
52. * not available *
53. * not available *
54. * not available *
55. * not available *
56. * not available *
57. * not available *
58. * not available *