Chapter 7: Earth and the Moon

Section: Introduction

1. What would be perhaps the most striking feature that a visiting traveler from outer space would notice on approaching Earth, having examined the rest of the solar system?

A) distinctive and impressive mountain ranges

B) large quantity of liquid water on the surface

C) earthquakes occurring on the solid parts of the surface

D) evidence of volcanoes and lava flow

2. The basic color(s) of Earth as seen from outer space (see Figure 7-1 in the text) is (are)

A) brown.

B) blue, white, and brown.

C) green and brown.

D) gray and white.

3. What percentage of the sunlight that falls on Earth is reflected into space?

A) almost 100% because of the significant cloud cover

B) 31%

C) almost none—most of the energy is absorbed to maintain the present surface temperature of Earth

D) 69%

4. What percentage of the sunlight that falls on Earth is absorbed by Earth rather than reflected into space?

A) almost 100%—the energy contributes significantly to the maintenance of the present surface temperature of Earth.

B) 69%

C) 31%

D) almost none—most of the energy is reflected out into space since the albedo of Earth is relatively high.

5. If Earth is known to have an average albedo of 0.31, what percentage of the sunlight hitting Earth is absorbed by it?

A) 100% – 0.31% = 99.69%—that is, most of it

B) 31%

C) 0.31%, or very little—most of it is reflected into space.

D) 69%

6. Earth’s “albedo” is the fraction of radiant energy from the Sun that Earth re-radiates into space. This number

A) is constant; it does not vary on a daily or seasonal basis.

B) varies as Earth rotates, but the daily variation does not change with the seasons.

C) varies with the seasons but is constant during any 24-hour rotation.

D) varies both daily and seasonally.

7. How does Earth’s albedo compare with those of Mars and Venus?

A) All terrestrial planets have about the same albedo.

B) Earth has the highest albedo of the three.

C) Earth has the lowest albedo of the three.

D) Earth’s albedo is less than that of Venus but greater than that of Mars.

Section: 7-1

8. Which is the MOST abundant gas in Earth’s atmosphere?

A) oxygen

B) nitrogen

C) hydrogen

D) carbon dioxide

9. What is the approximate ratio of nitrogen to oxygen in Earth’s atmosphere?

A) 1 part nitrogen to 2 parts oxygen

B) 4 parts nitrogen to 1 part oxygen

C) 1 part nitrogen to 4 parts oxygen

D) equal parts nitrogen and oxygen

10. One of the major differences between Earth and its neighboring planets Venus and Mars is the lack of large quantities of CO₂ in its atmosphere. If all three planets were originally formed with significant quantities of this gas in their atmospheres, where is the majority of this CO₂ on Earth at the present time?

A) dissociated by UV and visible sunlight into carbon and oxygen that now exists in abundance as separate chemicals

B) concentrated high in the atmosphere where it contributes to the greenhouse effect

C) dissolved in seawater, a situation that cannot arise on the neighboring planets

D) locked up in carbonate and carbon-rich rocks and minerals formed in the sea and on Earth’s surface

11. What is the approximate ratio of the number of oxygen to nitrogen molecules in Earth’s lower atmosphere?

A) 1 oxygen molecule to every 4 nitrogen molecules

B) 4 oxygen molecules to every 1 nitrogen molecule

C) equal numbers of oxygen and nitrogen molecules

D) only 1 oxygen molecule to every 100 nitrogen molecules, or about 1%

12. The major constituents of Earth’s atmosphere are

A) 95% carbon dioxide and some water vapor.

B) about equal amounts of methane, ammonia, water vapor, and carbon dioxide.

C) about 80% oxygen and 20% nitrogen.

D) about 80% nitrogen and 20% oxygen.

13. The terrestrial planet whose atmosphere is composed primarily of nitrogen is

A) Mars.

B) Venus.

C) Jupiter.

D) Earth.

14. “It has a cool, solid surface with an atmosphere of nitrogen and oxygen and clouds of water vapor.” Which of the planets fits this description?

A) Mars

B) Mercury

C) Venus

D) Earth

15. The atmosphere breathed now is the _____ atmosphere Earth has had.

A) third

B) second

C) seventh

D) first

16. What were the dominant gases in Earth’s earliest atmosphere after it first formed?

A) methane and ammonia

B) hydrogen and helium

C) nitrogen and oxygen

D) carbon dioxide and nitrogen

17. What happened to Earth’s first atmosphere?

A) It remains part of its present atmosphere, although it has been mixed with nitrogen and oxygen.

B) It was blown away by an early flare-up of the evolving Sun.

C) Its molecules were moving too rapidly to be held by Earth’s gravitational pull.

D) It dissolved in the oceans as soon as these were formed.

18. Why did Earth’s earliest atmosphere, composed primarily of hydrogen and helium, NOT last long?

A) Hydrogen is highly reactive, and it soon became bound into chemical compounds in Earth’s rocks.

B) Hydrogen and helium are light gases, and they soon escaped into space.

C) Biological activity very quickly combined the hydrogen with oxygen to form water.

D) The hydrogen soon became dissolved in Earth’s oceans.

19. Earth’s secondary atmosphere was a hundred times as dense as its present atmosphere, yet the temperature was only sufficient to keep liquid water from freezing and not high enough to vaporize liquid water. Why wasn’t the temperature higher?

A) Earth formed beyond the snow line and migrated inward, and at this time it was too far from the Sun to be warm enough to vaporize water.

B) The developing Sun was not as hot as it is now.

C) The secondary atmosphere contained very little carbon dioxide, so there was not enough of a greenhouse effect to enhance the temperature.

D) The dense secondary atmosphere enhanced Earth’s albedo. With less radiation striking Earth, the temperature did not rise substantially.

20. What happened to the first major atmosphere to develop on the early Earth, which consisted of hydrogen and helium?

A) The molecules reacted chemically with Earth’s hot surface and were absorbed into the newly formed rocks.

B) The molecules were quickly absorbed into the ocean since they have high solubility in water.

C) The molecules combined chemically with one another to become molecules that were heavy enough for Earth’s gravity to pull into the surface rocks, where they are now found.

D) The atmosphere drifted off into space as Earth’s gravity was too weak to hold the light molecules of hydrogen and helium.

21. Earth’s secondary atmosphere contained a great deal of carbon dioxide, but its present atmosphere contains comparatively little. Where did this carbon dioxide go? Which of these statements does NOT explain what happened to a substantial fraction of this carbon dioxide?

A) The carbon dioxide escaped into space.

B) The carbon dioxide dissolved in the oceans.

C) The carbon dioxide became part of carbonate rocks.

D) The carbon dioxide was trapped underground

22. What were the dominant gases in Earth’s second atmosphere?

A) nitrogen and oxygen

B) carbon dioxide and water vapor

C) methane and ammonia

D) hydrogen and helium

23. Roughly how much more massive was Earth’s second atmosphere compared with today’s atmosphere?

A) same mass as the present atmosphere

B) 1/10 as massive

C) twice as massive

D) 100 times as massive

24. Billions of years ago, Earth’s atmosphere was composed primarily of carbon dioxide. Where might one go on Earth to find a large fraction of this carbon dioxide today?

A) nowhere—most of the carbon dioxide has escaped into space

B) anywhere—most of the carbon dioxide is still in the atmosphere, but nitrogen and oxygen have since been added to it

C) to extinct volcanoes, which are composed of rock from Earth’s interior that absorbed the carbon dioxide earlier in Earth’s history

D) to mountain ranges such as the Rocky Mountains of North America, which are composed largely of limestone

25. Billions of years ago, Earth’s atmosphere was composed primarily of carbon dioxide. What happened to much of this carbon dioxide?

A) still in the atmosphere

B) dissolved into Earth’s oceans

C) broken down into carbon and oxygen by solar ultraviolet light

D) lost to space

26. Where did the majority of the large amount of carbon dioxide (CO₂) from the second major atmosphere to form on the early Earth end up?

A) as nitrogen oxides and carbon, after chemical reactions with the majority component of the atmosphere, the nitrogen molecules

B) absorbed by plant life and transformed into solid carbon and gaseous oxygen

C) dissolved in the oceans and, via the shells of living creatures, in the limestone of many mountain ranges

D) still in the atmosphere, but the quantity of nitrogen and oxygen has since risen to make these constituents the most abundant and relegate carbon dioxide to a minor constituent

27. One of the major differences between Earth and its neighboring planets Venus and Mars is the lack of large quantities of carbon dioxide in its atmosphere near the surface of the planet. If all these planets were originally formed with significant quantities of this gas in their atmospheres, where is this carbon dioxide on Earth at the present time?

A) concentrated high in the atmosphere, where it contributes to the greenhouse effect

B) dissociated by solar UV light into carbon and oxygen, which now exist in abundance as separate chemicals

C) locked up in rocks such as limestone, formed by life-forms in the sea and on Earth’s surface

D) dissolved in seawater, a situation that cannot arise on Venus or Mars

28. Which major constituent of the atmospheres of Venus and Mars is present in only very small amounts in Earth’s atmosphere?

A) methane, CH₄

B) carbon dioxide, CO₂

C) nitrogen, N₂

D) oxygen, O₂

29. Which of these processes was NOT important in helping to remove carbon dioxide from Earth’s early atmosphere?

A) biological activity

B) dissolving of carbon dioxide into the oceans

C) sedimentation of carbon compounds on the ocean floors

D) escape of carbon dioxide into space

30. Photosynthesis in plants on Earth maintains a balance between which of the two atmospheric gases?

A) carbon dioxide and water vapor

B) oxygen and water vapor

C) nitrogen and oxygen

D) oxygen and carbon dioxide

31. Photosynthesis is a chemical process that takes place in green plants. What is its effect on Earth’s atmosphere?

A) Photosynthesis consumes carbon dioxide from its atmosphere but produces carbon dioxide at the end of the process and thus has little effect on its atmosphere.

B) Photosynthesis consumes carbon dioxide from its atmosphere and produces oxygen.

C) Photosynthesis consumes oxygen from its atmosphere and produces carbon dioxide.

D) Photosynthesis consumes both water vapor and carbon dioxide from its atmosphere and produces nitrogen.

32. The presence of oxygen in Earth’s atmosphere is thought to result directly from what type of process?

A) volcanic eruptions

B) outgassing of the oceans

C) original condensation of interplanetary gas clouds

D) biological activity of plants and animals

33. The large amount of free oxygen in Earth’s present atmosphere is primarily a result of

A) outgassing by volcanoes and other geological processes.

B) biological processes such as photosynthesis.

C) splitting of carbon dioxide into carbon and oxygen by solar ultraviolet light.

D) carbon dioxide becoming dissolved in the oceans, releasing oxygen.

34. The molecular oxygen in Earth’s present atmosphere was MOST likely produced

A) at the formation of Earth and has always been present.

B) from volcanic eruptions as the primitive Earth cooled down.

C) from volcanoes, by outgassing.

D) by biological activity such as photosynthesis from green plants.

35. Which of these is true of the oxygen in Earth’s atmosphere?

A) Oxygen is the most abundant gas in Earth’s atmosphere.

B) Oxygen is very chemically reactive.

C) The oxygen in Earth’s atmosphere exists not as pure oxygen but only in chemical combination with hydrogen in water, carbon in carbon dioxide, and nitrogen in nitrogen oxides.

D) Oxygen is the heaviest molecule in Earth’s atmosphere.

36. Which of these statements about Earth is true?

A) The oxygen in Earth’s atmosphere was created by the evaporation of seawater and its dissociation into hydrogen and oxygen by solar UV light.

B) Earth has always had an oxygen-rich atmosphere, which was one reason that life could develop on Earth.

C) Outgassing by volcanic eruptions converted the carbon dioxide–rich atmosphere into an oxygen-rich atmosphere, thus creating conditions in which life could develop.

D) Life developed in a carbon dioxide–rich atmosphere and then converted it into an oxygen-rich atmosphere.

37. Which one of these statements about ozone is NOT correct?

A) It is triple oxygen, O₃.

B) It comprises most of Earth’s stratosphere.

C) It absorbs intermediate wavelength ultraviolet radiation from the Sun.

D) It causes the temperature in the stratosphere to rise with altitude.

38. Ozone in the stratosphere performs an important task that protects life on Earth. What is it?

A) Ozone absorbs the solar wind as it streams into Earth, thereby protecting life from dangerous ionizing radiation.

B) Ozone absorbs much of the dangerous solar ultraviolet light.

C) Ozone acts as a disinfectant, killing dangerous viruses and bacteria that drift in all the time from space before they can reach Earth.

D) Ozone absorbs infrared radiation, thereby providing a comfortable atmospheric temperature on the surface of Earth.

39. An “ozone hole” is

A) a region centered on the equator where ozone levels are always very low because of destruction by direct sunlight.

B) a region of the stratosphere, often above the South Pole, where ozone levels occasionally drop to very low levels.

C) the name given to small pits or holes on the aluminum surface of an aircraft, etched by the corrosive ozone encountered in the stratosphere and requiring regular maintenance.

D) a permanent region of very low ozone content in the stratosphere centered over the South Pole that has been there for thousands of years; the resulting transparency to UV radiation accounts for the lack of life-forms there.

40. What are ozone holes?

A) small voids on Earth’s ozone layer that occur randomly over the entire planet

B) regions of larger-than-normal ozone concentration that appear near the poles

C) regions of smaller-than-normal ozone concentration that appear near the poles

D) seasonal drops in ozone density scattered around the equator

41. What is the current status of Earth’s ozone layer?

A) The ozone layer is being irreversibly depleted and will probably disappear entirely within the next 200 years.

B) The ozone layer has been distorted—too thin at the poles and too thick over the equatorial regions.

C) The ozone layer has been somewhat depleted, but if left alone, it could restore itself in a century.

D) The ozone layer has become too thick and is moving downward toward the surface, where its heating qualities contribute to global warming.

42. Which of these terms does NOT label a region of Earth’s atmosphere or near-Earth environment?

A) ionosphere

B) troposphere

C) stratosphere

D) chromosphere

43. In which layer of Earth’s atmosphere is the ozone layer located?

A) mesosphere

B) stratosphere

C) thermosphere

D) troposphere

44. Ozone is a gas consisting of

A) molecules containing combinations of oxygen and nitrogen atoms and electrons.

B) a mixture of several chlorofluorocarbon gases (CFCs).

C) molecules containing 3 oxygen atoms.

D) ionized oxygen atoms, positively charged.

45. Earth’s stratosphere is warmer than the layers above and below it because

A) the methane released when fossil fuel is burned collects in this layer and absorbs infrared light.

B) warm air heated by contact with the ground rises into the stratosphere and heats it.

C) ozone in the stratosphere absorbs specific wavelengths of ultraviolet radiation from the Sun.

D) carbon dioxide in the stratosphere absorbs infrared light radiated outward by the ground.

46. Why does the temperature in the stratosphere increase with increasing altitude?

A) The stratosphere is heated by solar ultraviolet radiation absorbed by the ozone layer.

B) Charged particles from the magnetosphere collide with atoms in the stratosphere, depositing energy.

C) Higher altitudes are closer to the Sun and are therefore heated more by it.

D) The stratosphere is heated by solar infrared radiation absorbed by carbon dioxide and water vapor.

47. The gas temperature in the stratosphere of Earth’s atmosphere reaches a maximum at about 50 km. The cause is

A) the absorption of solar ultraviolet radiation by ozone (O₃)_.

B) heating by auroral activity higher in the atmosphere.

C) the ionization of oxygen and nitrogen by solar ultraviolet radiation.

D) turbulence, caused by wind and weather.

48. What is the MOST important reason for Earth’s need for the ozone layer?

A) The ozone layer protects Earth from the solar wind.

B) The ozone layer allows long-distance radio communication by reflecting radio waves to Earth’s surface.

C) The ozone layer shields Earth from harmful solar ultraviolet radiation.

D) The ozone layer provides a convenient dumping site for chlorofluorocarbon chemicals, which are harmful to life.

49. The chemical constituent that absorbs UV radiation in the stratosphere of Earth’s atmosphere, thereby heating these layers to relatively high temperatures, is

A) N₂, nitrogen.

B) CO_2, carbon dioxide.

C) H₂O, water vapor.

D) O₃, ozone.

50. Which of these events would NOT be a consequence of the destruction of the ozone layer on Earth?

A) large-scale (perhaps total) destruction of life on Earth

B) large-scale freezing of the oceans

C) drastic increase in ultraviolet radiation at Earth’s surface

D) elimination of the rise in temperature in the stratosphere

51. What are the major layers of Earth’s atmosphere in the correct order from the surface upward?

A) stratosphere, mesosphere, thermosphere, troposphere

B) mesosphere, troposphere, thermosphere, stratosphere

C) thermosphere, mesosphere, troposphere, stratosphere

D) troposphere, stratosphere, mesosphere, thermosphere

52. What is the basic structure of Earth’s atmosphere?

A) single layer of smoothly decreasing temperature with increasing altitude

B) four layers of alternating temperature profiles: temperature decreasing, then increasing, then decreasing, then increasing with altitude

C) single layer of smoothly increasing temperature with increasing altitude

D) two layers: temperature decreasing with increasing altitude in the lower layer, then increasing with increasing altitude in the upper layer

53. How does the temperature of Earth’s atmosphere vary with height over the range 0–80 km?

A) The temperature decreases, then increases, then decreases again.

B) The temperature rises steadily until it reaches a high and constant value above 80 km.

C) The temperature increases, then decreases, then increases again.

D) The temperature decreases steadily until it reaches a minimum at 80 km.

54. The lowest temperature in Earth’s atmosphere is about

A) 3 K.

B) 20 K.

C) 200 K.

D) 273 K.

55. The lowest temperature in Earth’s atmosphere occurs at an altitude of about

A) 80 km.

B) 50 km.

C) 10 km.

D) 0 km (the surface of Earth).

56. The coldest layer of Earth’s atmosphere is located between the

A) mesosphere and ionosphere.

B) troposphere and Earth’s surface.

C) stratosphere and mesosphere.

D) troposphere and stratosphere.

57. Earth’s thermosphere is the

A) outermost atmospheric layer in which ultraviolet light from the Sun ionizes atoms.

B) intermediate atmospheric layer in which ultraviolet light from the Sun is absorbed by ozone (O₃) molecules.

C) region of the magnetosphere in which trapped high-energy charged particles spiral along magnetic field lines.

D) layer of molten iron and nickel below the mantle.

58. What is the lowest layer in Earth’s atmosphere?

A) thermosphere

B) magnetosphere

C) troposphere

D) stratosphere

59. In which layer of Earth’s atmosphere does weather occur?

A) stratosphere

B) mesosphere

C) thermosphere

D) troposphere

60. The hottest part of Earth’s atmosphere is the

A) lowest layer of the troposphere (near Earth’s surface).

B) boundary of the upper troposphere with the stratosphere.

C) upper mesosphere.

D) upper ionosphere.

61. The temperature decreases as one moves upward in the troposphere. This is also true in

A) no other atmospheric layer.

B) the stratosphere.

C) the mesosphere.

D) the ionosphere.

62. What happens to the temperature as one goes upward in Earth’s ionosphere?

A) The temperature drops as one gets farther from the warm Earth.

B) The temperature drops because the faster (warmer) molecules escape into space, leaving behind the slower (colder) molecules.

C) The temperature rises because of the absorption of ultraviolet energy by the ozone layer.

D) The temperature rises because of the absorption of ultraviolet energy ionizes molecules.

63. The troposphere of Earth is the

A) atmospheric layer closest to the ground.

B) atmospheric layer above the mesosphere.

C) uppermost layer of solid rock below the planet’s crust.

D) atmospheric layer that contains the highest concentration of ozone.

64. A person is on a commercial airliner flying across the North Atlantic. They are MOST likely near the top of the

A) troposphere.

B) stratosphere.

C) mesosphere.

D) ionosphere.

65. What is pressure?

A) force times the area over which the force acts

B) force times the distance over which the force acts

C) same as force but expressed in different units

D) force divided by the area over which the force acts

66. What fraction of the total mass of Earth’s atmosphere is contained in the troposphere, the lowest layer of Earth’s atmosphere?

A) 50%

B) 25%

C) 10%

D) 75%

67. The pressure in the atmosphere of Earth (or of any other planet) is related to altitude above the planet’s surface in what characteristic way?

A) The pressure remains constant with increasing altitude.

B) The pressure decreases by a fixed fraction of each interval of altitude (down by half every 5.5 km on Earth).

C) The pressure decreases and increases several times with increasing altitude, following the temperature variation.

D) The pressure decreases by a fixed amount per unit altitude interval (20% of surface pressure every 5.5 km on Earth).

68. The pressure in the atmosphere of Earth varies with altitude by

A) decreasing smoothly with altitude, dropping by about half for every 5.5 km.

B) increasing over a small altitude range above the surface of Earth (about 1 km) and then decreasing smoothly with increasing altitude.

C) remaining a constant up to the height of the highest mountains, then decreasing rapidly.

D) decreasing and increasing several times with increasing altitude, following the temperature variation.

69. Air pressure falls by roughly a fraction of one-half its pressure for every 5.5-km increase in altitude. What, then, is the air pressure at the top of the troposphere, 11 km above Earth’s surface?

A) 33% of that at Earth’s surface

B) zero

C) 50% of that at Earth’s surface

D) 25% of that at Earth’s surface

70. How has the CO₂ concentration in Earth’s atmosphere changed over the past thousand years?

A) There are no means of measuring the CO₂ concentration in Earth’s atmosphere for times so far past.

B) The CO₂ concentration has remained absolutely constant.

C) The CO₂ concentration has increased steadily.

D) The CO₂ concentration was relatively constant for about 800 years but has increased significantly since 1800 A.D.

71. About how much has Earth’s surface temperature increased since 1000 A.D.?

A) It has remained absolutely constant.

B) 5°C

C) 0.6°C

D) 15°C

Section: 7-2

72. Who first postulated that continents drift around over Earth’s surface?

A) Charles Darwin

B) Alfred Wegener

C) J. Tuzo Wilson

D) James Van Allen

73. Which fact first gave Alfred Wegener the idea that continents have drifted and are still drifting over Earth’s surface?

A) The ocean floors were much younger than the continents, indicating that they were still being formed.

B) The shapes of the east coasts of North and South America fit nicely against those of the west coasts of Europe and Africa.

C) A system of mountains and faults running up the middle of the Atlantic seafloor showed evidence that the crust was spreading apart there.

D) Volcanoes and earthquakes were localized into a well-defined “ring of fire” around the Pacific Ocean and other areas.

74. The idea of continental drift, as proposed by Wegener around 1915, had one major flaw, which was

A) the absence of a source for the forces and energy required to move the continents.

B) the lack of any evidence that Africa and the Americas had ever been joined.

C) the recent discovery of seafloor spreading, which contradicted the theory.

D) the measured rate of continental motions, which were far greater than predicted.

75. How was the Mid-Atlantic Ridge formed?

A) Two crustal plates slid past each other in a transverse fault.

B) The weight of sediments caused the ocean floor to sink, and the ridge resulted from slumping toward the center of this basin.

C) Molten rock pushed up from Earth’s interior and forced two crustal plates apart.

D) Two crustal plates collided, causing one plate to buckle, forming the ridge, while the other plate was thrust down beneath it.

76. The Mid-Atlantic Ridge in Earth’s crust is a region where

A) two tectonic plates are pushing against one another, forcing the ridge upward.

B) two tectonic plates are slowly spreading apart.

C) one tectonic plate is moving below another in a process known as subduction.

D) a single hot plume is pushing molten magma or lava through a break in the crust.

77. The Mid-Atlantic Ridge is being produced by

A) the weight of the Atlantic Ocean on the thin seabed.

B) tidal flows of ocean water meeting in the mid-Atlantic.

C) two tectonic plates pushing together, producing upthrust.

D) two tectonic plates moving apart because of volcanic upflow.

78. The San Andreas fault in California is an example of

A) two tectonic plates pushing directly against one another.

B) an upthrust due to a hot spot in Earth’s mantle.

C) a spreading center, where two tectonic plates are being pushed away from each other.

D) two tectonic plates sliding past each other.

79. The Mid-Atlantic Ridge is an example of

A) a transformation-fault boundary.

B) a divergent boundary.

C) a convergent boundary.

D) None of these answers is correct.

80. In the modern theory of crustal motion on Earth’s surface, the process of seafloor spreading is described as the

A) motion of plates toward mid-oceanic ridges and away from continental boundaries.

B) motion of plates away from mid-oceanic ridges and toward continental boundaries.

C) northward motion of some plates and the southward motion of others, causing earthquakes where they slide past each other.

D) rotation of plates around axes that remain stationary on Earth causing plate-edge collisions.

81. The San Andreas fault in California is an example of

A) a transform fault boundary.

B) a divergent boundary.

C) a convergent boundary.

D) None of these answers is correct.

82. Approximately how many major tectonic plates make up Earth’s surface?

A) about a dozen

B) two

C) seven

D) hundreds

83. What is a typical speed of drift for a continent sliding over Earth’s surface?

A) a few centimeters per century

B) a few centimeters per year

C) a few centimeters per million years

D) a few meters per year

84. The average speed of motion of the plates on Earth’s surface is

A) very small, less than a millimeter per century.

B) about 10 meters per year.

C) a few centimeters per year.

D) a few centimeters per century.

85. The process of seafloor spreading and plate tectonic movement on Earth’s surface takes place at a speed of

A) a few meters per year.

B) a few centimeters per year.

C) a few centimeters per century.

D) less than a millimeter per year.

86. The existence of the Mid-Atlantic Ridge is evidence that Europe and North America are

A) moving closer together.

B) moving farther apart.

C) remaining a fixed distance apart.

D) floating on layers of basalt of significantly different densities.

87. The African and South American continents are separating at a rate of about 3 cm per year, according to the ideas of plate tectonics. If they are now 5000 km apart and have moved at a constant speed over this time, how long is it since they were in contact?

A) 1.7 million years

B) 170 million years

C) 170 thousand years

D) 1.7 billion years

88. What is the cause of the great mountain ranges on Earth, such as the Rockies, the Andes, and the Himalayas?

A) In the carving of continents during ice ages, the mountains were left behind as “islands” in a sea of glaciers.

B) Heat from Earth’s interior caused Earth’s crust to expand and then crumple.

C) Two tectonic plates are being pushed apart by molten rock that is being forced up between them.

D) Two tectonic plates that are moving at different velocities across the face of Earth collide.

89. The Himalayan Mountains in Asia were formed by

A) an ancient, mid-oceanic volcanic ridge now uplifted to become dry land.

B) folding of Earth’s crust where two crustal plates collided along a subduction zone.

C) asteroid impacts during the first billion years of Earth’s history.

D) shrinking and folding of Earth’s crust as Earth cooled and contracted.

90. The great mountain ranges of Earth have been produced by

A) collisions between tectonic plates.

B) volcanic eruptions.

C) asteroid impacts because they are just worn-down crater walls.

D) wrinkling of the crust as the interior cools and contracts.

91. Great mountain ranges are generally a sign of

A) a transformation-fault boundary.

B) a divergent boundary.

C) a convergent boundary.

D) None of these answers is correct.

92. To what does the name “Pangaea” refer?

A) tectonic plate on which most of North America is riding

B) outer life-bearing layer of Earth, including the soil, oceans, and atmosphere

C) supercontinent on a tectonic plate that split into the present North America, South America, Europe, and Africa

D) ocean that covered most of North America millions of years ago

93. The supercontinent Pangaea is believed to have been

A) a myth, part of the Atlantis legend.

B) the first continent to rise from the sea, which broke up 200 million years ago.

C) the result of a collision of continents, of a type that occurs roughly every 500 million years.

D) the original surface of Earth, before the oceans formed.

94. What is (or was) Pangaea?

A) the original supercontinent that was formed when Earth’s surface solidified

B) the most recent of a number of supercontinents that have formed since Earth’s surface solidified

C) the name given to the future supercontinent that will form if the continental plates continue to follow their present paths

D) the site of the international conference at which Wegener presented his theory of continental drift

95. In what way are the supercontinents Laurasia, Pangaea, and Gondwana related?

A) An earlier, larger supercontinent split into Laurasia, Pangaea, and Gondwana.

B) Laurasia split into Gondwana and Pangaea.

C) Gondwana split into Pangaea and Laurasia.

D) Pangaea split into Gondwana and Laurasia.

96. All the boundaries of the major interacting tectonic plates on Earth’s surface are coincident with

A) regions of great biological activity and growth.

B) regions where ocean depths are greatest.

C) the edges of the continental shelves around the major continents.

D) the positions of maximum earthquake occurrence.

97. On Earth, the majority of earthquakes occur

A) along regions of greatest thermal stress in arctic and antarctic regions.

B) in the centers of tectonic plates (e.g., North American continent).

C) along the boundaries of major tectonic plates.

D) along the zone of maximum tidal stress around the equator.

98. Most of Earth’s earthquakes occur

A) where crustal plates are colliding, separating, or sliding past one another.

B) only where crustal plates are colliding head-on.

C) only where crustal plates are sliding past each other, as in the San Andreas fault.

D) more or less evenly over the entire Earth’s surface.

99. Which of these places on Earth experiences frequent earthquakes and volcanic activity because of its location? See Figure 7-8 in the text.

A) central Canada

B) Australia

C) Brazil

D) Alaska

100. Which two tectonic plates are slowly separating from each other on Earth’s surface along the Mid-Atlantic Ridge in the South Atlantic? See Figure 7-8 in the text.

A) African and Eurasian plates

B) Nazca and Pacific plates

C) South American and African plates

D) Pacific and Australia-India plates

101. Against which tectonic plate is the Australia-India tectonic plate pushing to form the Himalayan mountains? See Figure 7-8 in the text.

A) Eurasian Plate

B) North American Plate

C) African Plate

D) Antarctic Plate

Section: 7-3

102. The long and high mountain ranges found in the centers of several major oceans on Earth, such as the Mid-Atlantic Ridge, are caused by

A) continuous and steady erosion of the seabed on either side of the mountains by powerful sea currents flowing across the oceans, such as the Gulf Stream in the Atlantic.

B) lava upflow as the tectonic plates on the seafloor split apart and separate.

C) rebound of the surface of Earth in the centers of the large craters that became the ocean basins after the impacts of the large planetesimals or asteroids early in Earth’s history.

D) upthrust and buckling caused by seafloor motions from the continents toward the ocean centers, equivalent to the production of continental mountain ranges such as the Rockies.

103. Subduction on Earth is the process by which

A) cool surface material on Earth sinks below other material at a tectonic plate boundary.

B) dense material sank while lighter material rose to the surface during the early geological history of Earth.

C) molten lava oozes out between two tectonic plates that are spreading apart.

D) volcanic material emerges from the deep interior at a volcanic island such as Hawaii.

104. Which of these features on Earth’s surface is NOT an indication of plate tectonic motion either in the past or at present?

A) “ring of fire” around the Pacific Ocean, where volcanoes and earthquakes are common

B) deep ocean trenches found in certain regions of Earth’s surface

C) layered structure of the rocks of many mountain ranges such as the Rocky Mountains

D) presence of mountain ranges such as the Andes and the Himalayas in certain areas of Earth

105. The motions of large portions of Earth’s surface, the plates, are caused by

A) pressure variations in Earth’s atmosphere, both daily and seasonal.

B) tidal flow in oceanic waters.

C) flexing of Earth’s surface due to solar heating and nighttime cooling.

D) convective flow of material in Earth’s interior.

106. Which of these statements correctly describes the surface of Earth?

A) Individual, solid crustal plates are pushed around by Earth’s rotation and the tidal forces of the Moon and the Sun.

B) A thin, deformable crust allows the continents to slide over it.

C) Individual and separate solid crustal plates are pushed around by convective motion in the material of the underlying mantle.

D) A thick, solid crust keeps the continents and ocean floors in fixed positions with respect to one another.

107. “Continental drift” on Earth is now thought to be caused by

A) tidal flexing of Earth’s solid crust by the Moon’s gravitational pull.

B) circulation currents in the deep interior, causing slabs of Earth’s crust to move slowly.

C) precession of Earth’s spin axis.

D) the forces of oceanic tides on the continental shelves around the landmasses.

108. Continental drift on Earth is a result of

A) water percolating down through geological fault zones, acting both as a lubricant and as a hydraulic pump.

B) the momentum of impacts from large meteorites hitting the early Earth.

C) large-scale circulation of partly molten or plastic rock in Earth’s interior.

D) flexing of Earth’s surface by lunar and solar tides.

109. Which one of these processes was important for melting the entire Earth about 4.6 billion years ago?

A) heat released by the condensation of water vapor into liquid water to form the ocean

B) radioactivity, or the spontaneous breaking apart of heavier nuclei into lighter ones

C) nuclear fusion, or the combining of lighter nuclei to form heavier ones

D) tidal heating of Earth due to the combined gravitational pulls of the Sun and the Moon

110. Geologists have found that the upper layers of the mantle are “plastic.” Why is this important?

A) Plastic is an important resource for the future.

B) These layers can easily crack to allow pent-up heat and energy to escape.

C) These layers can easily bend to accommodate oceans and mountains.

D) The continents are able to float and drift on these layers.

111. The early Earth remained molten longer than an inert mass its size might have been expected to if left undisturbed. Which of these is processes is NOT thought to have contributed to this longevity?

A) impact of space debris

B) natural radioactive decay

C) nuclear fission

D) nuclear fusion

112. To what does planetary differentiation refer?

A) large-scale convection of molten rock in the mantle of a planet, which on Earth causes continental drift

B) sinking of heavier elements toward the center of a planet and the floating of lighter elements toward the surface

C) circulation of iron in the core of a planet, resulting in the generation of a magnetic field

D) formation of rocky planets in the hotter, inner solar system and gas giants in the colder, outer regions

113. The process by which heavier materials sank into the centers of terrestrial planets while lighter material rose to the surfaces early in the history of these planets is known as

A) hot-spot volcanism.

B) planetary differentiation.

C) seafloor spreading.

D) subduction.

114. Which of these mechanisms is MOST likely to have taken place while Earth was molten to form the present structure of Earth?

A) All materials were thoroughly mixed by convection in the molten state, and Earth remained mixed as it cooled.

B) Hydrogen and helium became highly compressed by gravity and sank to the core below a layer of heavier rocky material.

C) Lighter elements sank to the center, leaving the heavier material to form the rocky surface as cooling proceeded.

D) Heavy elements sank to the center under gravity while lighter materials rose to the surface and solidified into rocks.

115. Why is it that terrestrial planets are thought to have dense iron cores?

A) Thermonuclear reactions produced iron as a fusion product in the earlier phases of planetary evolution (thermonuclear accretion).

B) During the formation of the planets, heavy elements accumulated first, followed by the accretion of lighter elements onto them (bimodal accretion).

C) The planets were molten early in their lives, and the heavy elements sank and lighter materials floated to the surface (planetary differentiation).

D) Magnetism in the iron was sufficiently powerful to pull iron atoms to the center as the planet formed (magnetic sorting).

116. Why is the core of Earth made up predominantly of the heavy element iron?

A) Chemical processes refined iron from iron oxides and other compounds in primordial rocks at the high temperatures of Earth’s core, similar to present-day iron ore processing.

B) Nuclear reactions in the very hot early core of Earth produced iron from lighter elements by nuclear fusion.

C) The heavy elements sank slowly to the center during early molten phases in Earth’s geological history.

D) The heavy elements came together first out of the primordial dust and gas to form the initial Earth because of their greater density and gravitational attraction, and this core then attracted lighter rocks to its surface.

117. In the current picture of Earth’s interior, how is temperature thought to change with depth?

A) There is a steady increase of temperature with depth.

B) There is a structure of several layers similar to Earth’s atmosphere in which temperature first increases with depth and then decreases and then reverses several more times.

C) The temperature rises only slightly through the mantle, then soars as the core is approached.

D) There is a layer of radioactive materials at the base of the mantle. The temperature increases slowly as one approaches this layer, then it rises sharply through this layer, and then it rises slowly again below this layer.

118. At Earth’s surface, iron melts at 1250 K, and the temperature at Earth’s core is approximately 5000 K. Which of these statements correctly characterizes iron in Earth’s core?

A) Clearly, Earth’s iron core is completely molten.

B) Because the melting temperature of iron depends also on the pressure to which it is subjected, it turns out that Earth’s iron core is completely solid.

C) Because the pressure and temperature both vary with depth, it turns out that only the inner part of Earth’s iron core is solid. This is surrounded by a liquid iron outer core.

D) Because the pressure and temperature both vary with depth, it turns out that only the inner part of Earth’s iron core is molten. This is surrounded by a solid iron outer core.

119. Which of these models of Earth’s interior is now considered to be the MOST likely description of the actual Earth?

A) solid core, within a molten outer core, rotating more rapidly than the rest of Earth

B) solid core within a molten outer core, the whole system rotating at exactly the same rate as the outer mantle and crust

C) solid core, within a molten outer core, rotating more slowly than the rest of Earth

D) totally fluid interior rotating at the same rate as the outer mantle and crust

120. Seismic evidence suggests that Earth’s core spins about 2° more per year than the surface. In roughly how many years will the surface and the core have the same relative orientation they do today?

A) 2

B) 50

C) 90

D) 180

121. Where is the mantle of Earth located?

A) outside but in contact with the crust, that is, the oceans and the atmosphere

B) between the core and the crust

C) between the stratosphere and the thermosphere

D) in the outermost atmosphere and beyond, where the planet’s magnetic field captures solar wind particles

122. The mantle of Earth is composed of

A) atmospheric gases.

B) water.

C) rock.

D) iron.

123. Earth’s mantle, the semimolten layer below the crust, is composed largely of what chemical materials?

A) iron-poor rocks and minerals

B) mostly pure iron

C) solid hydrogen and helium

D) minerals rich in iron and magnesium

124. Earth has an average density that is approximately

A) twice that of water.

B) equal to that of water.

C) more than 10 times that of water.

D) 5 times that of water.

125. The core (inner and outer) of Earth extends over what fraction of its radius?

A) almost 80%

B) roughly

C) less than 10%

D) about

126. What is the basic structure of Earth’s interior?

A) solid iron inner core, molten iron outer core, rocky mantle, lighter rocky crust

B) molten iron inner core, molten rocky outer core, solid rocky mantle, lighter rocky crust

C) molten iron core, molten rocky mantle, solid rocky crust

D) molten iron inner core, solid iron outer core, rocky mantle, lighter rocky crust

127. The internal structure of Earth is a

A) core of solid rock extensively enriched in iron, surrounded by a solid mantle of pure rock.

B) large, solid iron core surrounded by a thick, flexible mantle of rock.

C) core of rock and iron, surrounded by a mantle of liquid hydrogen.

D) large core of iron, partly solid and partly molten, surrounded by a thick, flexible mantle of rock.

128. Of what material is the core of Earth composed?

A) mostly iron

B) roughly half rock and half iron

C) titanium and nickel

D) rock of similar composition to that in the crust, but much denser

129. The chemical makeup of the central core of Earth is considered to be

A) sulfur-rich minerals compressed to a high density.

B) rocky minerals rich in iron.

C) mostly iron.

D) very close to the chemical makeup of the surface—silicon-rich rocks and minerals.

130. What is believed to be the composition of Earth’s core?

A) about 80% iron and 20% lighter elements

B) about iron and lighter elements

C) about half iron and half lighter elements

D) essentially pure iron

131. The waves that geologists and geophysicists use to probe the inside of Earth are

A) seismic waves.

B) X-rays.

C) gravitational waves.

D) radio waves.

132. Which scientific approach gives the MOST information about the deep interior of Earth?

A) deep drilling of exploratory holes for science and mineral recovery (e.g., oil)

B) study of lava flows from volcanoes

C) measurement of cosmic neutrinos, which pass very easily through Earth

D) worldwide measurement of low-frequency seismic waves produced by earthquakes

133. Which of these techniques is the primary one used by geologists and geophysicists to probe the structure of Earth’s core and mantle?

A) X-ray analysis from satellites

B) extrapolation of surface features (e.g., mountain chains) into the deep interior

C) direct sampling of interior rock by deep drilling through the ocean floor

D) study of the deflection of seismic waves from earthquakes

134. What effect, if any, does the pressure to which a material is subjected have on the melting temperature of the material?

A) There is no effect of pressure on melting temperature.

B) Within Earth’s interior the pressure is decreased (compared to the surface), causing the melting temperature to increase (compared to the surface).

C) Within Earth’s interior the pressure is increased (compared to the surface), causing the melting temperature to decrease (compared to the surface).

D) Within Earth’s interior the pressure is increased (compared to the surface), causing the melting temperature to increase (compared to the surface).

135. What effect does an increase in pressure have on the temperature at which rock melts?

A) It is not yet known—the temperature needed to melt rock has not yet been achieved in the laboratory.

B) An increase of pressure increases the melting temperature.

C) An increase of pressure has no effect on the melting temperature because the melting temperature is independent of pressure.

D) An increase of pressure lowers the melting temperature.

136. The material of Earth’s interior becomes molten at _____ km below the surface.

A) 5200

B) 300

C) unknown. This statement is erroneous because nowhere is the interior molten.

D) 2900

137. The depth from the surface of Earth to the top of its liquid core is about _____ km.

A) 2900

B) 6400

C) 5000

D) 30

138. Earth’s solid inner core results from the fact that the

A) outer core is heated and melted by friction between the core and the mantle, and this heating does not extend to the inner core.

B) melting temperature of an iron-nickel mixture increases with increasing pressure and rises above the actual temperature in the inner core.

C) inner core has a different composition than the outer core, with a higher melting temperature.

D) temperature of the inner core is lower than the temperature of the outer core, producing a temperature inversion.

139. The outer core of Earth is molten, but the inner core is solid. The reason is that the

A) inner core has a different composition than the outer core, with a higher melting point.

B) lower pressure in the inner core allows the material to freeze out of the molten rock.

C) melting point of the iron-nickel mixture is raised above the actual temperature by the extremely high pressure.

D) temperature is lower in the inner core than in the surrounding region.

140. Which of these phrases correctly describes the mantle of Earth?

A) molten iron

B) solid rock that is hot enough to become semimolten and “plastic”

C) molten rock

D) solid, immovable rock upon which the crustal plates can slide

141. Which of these clauses correctly describes the mantle of Earth?

A) hot, semimolten rock that flows upward in hotter parts of the mantle and downward in cooler parts

B) hot, semimolten rock that flows downward in hotter parts of the mantle and upward in cooler parts

C) hot, semimolten rock that flows upward at the equator and downward at the poles because of Earth’s rotation

D) hot, semimolten rock that flows downward at the equator and upward at the poles because of Earth’s rotation

142. What is the relationship between the mantle and the crust of Earth?

A) The crust sits motionless on top of the mantle and does not interact with it.

B) Convection in the mantle moves the continents around, but there is no transfer of material from the mantle to the crust or vice versa.

C) New layers of crust are formed when magma from the mantle flows out over old crust, and this old crust remains as the lowest level of the crust.

D) New crust is formed by magma rising from the mantle in some places, and old crust is pushed back down into the mantle in other places.

143. One of the principal difficulties in establishing the theory of continental drift (the idea that tectonic plates drift around on Earth’s surface) was identifying a source of energy capable of powering such movement. What is now believed to be the source of such energy?

A) neutrinos interacting with Earth’s interior

B) heat trapped by the greenhouse effect

C) hot material welling up from Earth’s interior

D) the tidal pull of the Moon and the Sun

144. The heat energy that powers tectonic activity on the surface of Earth originates deep in Earth’s core. How does the majority of this energy move from the core to the surface?

A) conduction through the solid lower mantle and convection in the upper mantle (asthenosphere)

B) convection throughout the entire mantle

C) conduction throughout the entire mantle

D) steady flow of hot magna from Earth’s core through cracks in the mantle to the lithosphere

Section: 7-4

145. The magnetic field of Earth

A) is related to its rotation around its axis.

B) has been almost constant throughout history.

C) is associated with magnetic poles that are at the same locations as the geographic poles.

D) is unique: It is the only planetwide magnetic field in the solar system.

146. The theory that describes how Earth’s magnetic field is created

A) is called the dynamo theory and is well established.

B) depends on Earth’s interaction with the Sun.

C) depends heavily upon friction between the surface and the atmosphere.

D) is still being developed.

147. The alignment and stability of Earth’s magnetic field over geological times can be described by stating that Earth’s magnetic axis

A) is inclined to the planet’s spin axis; this alignment varies, and the field has reversed frequently in geological times.

B) is closely aligned to Earth’s spin axis and has remained this way since early in Earth’s history.

C) has had a slowly varying inclination with respect to Earth’s spin axis with no abrupt changes, so Earth’s magnetic poles have drifted slowly throughout its geological history.

D) has a fixed alignment of about 11° with respect to Earth’s spin axis but has flipped or reversed completely many times in geological times.

148. For a period of 4000 years or so while Earth’s magnetic field was reversing direction, the planet has little or no magnetic field. What is one consequence of this?

A) more coronal mass ejections

B) brighter auroras

C) increased depletion of its atmosphere

D) a decreased rotation rate

149. The alignment of Earth’s rotation axis and its magnetic axis

A) are in the same direction.

B) are different by about 11.3°. Throughout history, it is believed, the magnetic axis has precessed slowly about the rotation axis at this 11.3° angle.

C) are different, and Earth is the only planet which has its rotation axis and its magnetic axis in different directions.

D) are different, as is the case with many of the other planets in the solar system.

150. The generation of Earth’s magnetic field, while not completely understood, is MOST likely influenced by

A) the flow of electrons and ions constituting an electric current in Earth’s magnetosphere.

B) electric currents in Earth’s electricity-conducting molten core.

C) permanent magnetism in Earth’s crustal rocks and the iron core.

D) electric currents in Earth’s semisolid mantle induced by the motion of the solar wind flowing around Earth.

151. The creation of the magnetic field of Earth is thought to be influenced by

A) a magnetized solid iron core in Earth’s interior.

B) the flow of solar wind particles around and within Earth’s outer atmospheric region, the magnetosphere, which produces an equivalent electric current.

C) electric currents flowing in the electricity-conducting liquid core of Earth.

D) localized magnetic anomalies, frozen into place in the crust near Earth’s surface.

152. Earth’s magnetic field protects Earth and its inhabitants from

A) the high-energy cosmic rays or hydrogen nuclei moving through the universe.

B) the majority of tiny but high-speed micrometeorites, which otherwise would crater Earth and cause significant damage to property.

C) a significant proportion of the solar neutrinos, the enormous flux of which could otherwise produce damage to genetic material in life-forms.

D) the solar wind, which would otherwise irradiate and damage life-forms if not deflected.

153. Earth’s magnetosphere is the

A) region beyond Earth’s atmosphere where Earth’s magnetic field protects it from the solar wind.

B) region in Earth’s crust near each magnetic pole.

C) molten core of Earth, whose motions produce the magnetic field.

D) atmospheric layer between the stratosphere and thermosphere where motions are governed by Earth’s magnetic field.

154. Where are Earth’s Van Allen radiation belts located?

A) in the magnetosphere

B) in the stratosphere

C) in the molten iron core

D) in the atmosphere above the auroral regions, centered over the north and south magnetic poles

155. What are the Van Allen belts?

A) regions in the outer solar system beyond Pluto where comets are thought to originate

B) dark regions in Jupiter’s atmosphere circling the planet parallel to the equator

C) regions of intense earthquake activity along tectonic plate boundaries on Earth

D) regions of high-energy, charged particles in Earth’s magnetosphere

156. What are the Van Allen belts?

A) two doughnut-shaped regions of high-energy charged particles in Earth’s magnetosphere

B) oval-shaped region around each of Earth’s magnetic poles where charged particles collide with ions in Earth’s atmosphere

C) inner and outer parts of the asteroid belt

D) regions of high concentration of electrons and ionized atoms in Earth’s upper atmosphere where radio waves are reflected toward the surface of Earth

157. What is the name given to the two doughnut-shaped regions where high-energy charged particles are trapped by Earth’s magnetic field in Earth’s magnetosphere?

A) Van Allen belts

B) auroral ovals

C) ionospheric E and F layers

D) ozone layers

158. What causes the phenomenon of the aurora?

A) Solar ultraviolet light excites ozone molecules in the ozone layer.

B) Charged particles from the magnetosphere strike atoms in the upper atmosphere, causing them to emit characteristic colors of light.

C) Light from solar flares reflects from high-altitude clouds in Earth’s atmosphere.

D) Charged particles emit light as they spiral along magnetic field lines in the magnetosphere.

159. Which one of these is NOT a consequence of Earth’s magnetic field?

A) the Van Allen belts

B) the aurora

C) protection from the solar wind (which might otherwise deplete Earth’s atmosphere)

D) a partially liquid, rotating iron core

160. Auroras on Earth are caused by

A) reflection of sunlight from the Arctic and Antarctic ice into the polar skies.

B) electrons accelerated by electric currents in the ionosphere and then deposited into Earth’s atmosphere.

C) high-energy charged particles from the magnetosphere guided by Earth’s magnetic field into polar regions of the atmosphere.

D) ultraviolet radiation from the Sun exciting and ionizing atoms in Earth’s upper atmosphere to emit characteristic colors of light.

161. Auroral displays are MOST often seen

A) at the north and south geographical poles, along Earth’s spin axis.

B) directly above the north and south geomagnetic poles.

C) in two bands on either side of the equator, in the tropics.

D) in circular regions around the north and south geomagnetic poles.

162. The auroral display of northern and southern lights high in Earth’s atmosphere is caused by

A) solar wind electrons hitting the high atmosphere after being accelerated in the magnetic fields of the magnetosphere.

B) fluorescence caused by absorption of solar ultraviolet light by ozone molecules.

C) reflection of sunlight from the ice in the polar regions.

D) sunlight scattered by very high atmospheric clouds.

163. The source of the aurora (northern/southern lights) on Earth is

A) natural decay of radioactive elements.

B) reflection of sunlight off the polar ice sheets.

C) small meteorites burning up in Earth’s atmosphere.

D) charged particles trapped by Earth’s magnetic field interacting with the atmosphere.

164. Coronal mass ejections can have all of these effects EXCEPT to

A) send charged particles through the Van Allen belts into Earth’s atmosphere.

B) partially deplete the ozone layer.

C) disturb radio transmissions.

D) reverse the particle flow in Earth’s magnetosphere.

165. Which one of these does NOT appear to add to the depletion of the ozone layer?

A) some formerly common refrigerants

B) CFCs (chlorofluorocarbons)

C) coronal mass ejections

D) the aurora

Section: 7-5

166. The names used for the Moon’s maria were

A) first used in very ancient times and are mentioned in the Bible and the Koran.

B) assigned by the ancient Greeks.

C) invented a few hundred years ago after the first telescopic observations of the Moon.

D) assigned only recently, after the Apollo missions.

167. Many of the maria on the Moon appear to be

A) former ocean basins from which the water has escaped.

B) lava flows around giant ancient volcanoes.

C) craters filled with basalt from within the Moon.

D) evenly distributed on the near side and the far side of the Moon.

168. Which of these statements about the Moon is INCORRECT?

A) All studied craters were formed by collisions.

B) Most craters are round-rimmed, indicating high-speed impacts.

C) Older craters are surrounded by darker ejecta blankets.

D) About one- third of craters examined appear to be volcanic in origin.

169. Craters are not apparent on Earth at the present time in the abundance seen on the Moon because

A) plate tectonics has returned cratered surface layers into Earth’s interior, and weathering has obliterated the more recent craters.

B) the Moon protected Earth from impacts, which resulted in the craters and maria on the Moon.

C) all the potentially damaging interplanetary bodies were stopped by Earth’s atmosphere.

D) interplanetary objects have avoided Earth during its history.

170. Rilles on the Moon appear to be collapsed tunnels. Planetary scientists believe these tunnels were originally filled with

A) liquid water.

B) molten rock.

C) steam.

D) carbon dioxide.

171. What is the diameter of the Moon compared with the diameter of Earth?

A) about 1/4 of the diameter of Earth

B) less than 1/100 of the diameter of Earth

C) about 1/10 of the diameter of Earth

D) just over 1/2 the diameter of Earth

172. Which of these processes has played the greatest role in shaping the surface of the Moon?

A) impacts of interplanetary bodies of all sizes

B) motions of tectonic plates, producing mountain ranges wherever they collide

C) erosion by wind and atmospheric gases

D) recent volcanic activity, producing large numbers of craterlike volcanic calderas

173. What is the origin of the majority of lunar craters?

A) impacts by meteoric material

B) surface collapse after loss of groundwater by evaporation

C) volcanic explosions

D) impacts by space probes from Earth

174. Most of the craters on the Moon were formed by

A) water erosion, followed by evaporation early in the Moon’s history, leaving behind the empty basins, the maria, and craters.

B) a nuclear war in which the lunar inhabitants wiped themselves off the face of the Moon.

C) bombardment by interplanetary meteoritic material.

D) volcanic action; the craters are the old calderas of volcanoes.

175. Earth is much larger than the Moon, yet it has far fewer craters. Which statement is NOT an explanation for the disparity in crater numbers?

A) Earth’s atmosphere caused many smaller impactors to burn up before striking the surface.

B) Some older craters on Earth were worn away by the action of wind and rain.

C) Some older craters on Earth were eradicated as parts of the crust are constantly subducted.

D) Earth’s larger gravity tends to focus the orbits of near misses so that they hit the Moon instead.

176. The vast majority of lunar craters were caused by

A) lunar quakes, under gravitational tidal disturbance from Earth.

B) bombardment by objects of various sizes from space.

C) the explosion of rocks under the thermal shock from alternating intense sunlight in daytime to the cold of space at night.

D) volcanic eruptions from the Moon’s interior.

177. Most of the craters on the Moon are thought to have been caused by

A) collapse of volcanic domes, leaving central peaks in the craters.

B) volcanic activity, leaving behind volcano craters similar to those on Earth.

C) continuous bombardment throughout the Moon’s life, including the present and recent past, by large and small asteroids.

D) intense bombardment by large and small bodies over some specific early period in the Moon’s history.

178. Which of these is the LEAST common feature of lunar craters?

A) a central peak

B) an oval shape

C) an ejecta blanket

D) terraced crater walls

179. Why do the larger craters on the Moon have central peaks?

A) The impact cracked the crust, and lava flowed into the center of the crater, forming a small volcanic peak.

B) The incoming projectile was large enough that it was not destroyed and remained to form the central peak.

C) Debris from the crater walls has rolled into the crater and has collected at its center.

D) The crater floor rebounded upward after the initial compression from the impact of an interplanetary rock.

180. Many craters on the Moon are characterized by a central peak. What is its significance?

A) The central peaks are strong evidence that lunar craters are volcanic in origin.

B) A central peak is characteristic of an impact crater formed by a large object.

C) The crater has dug into the lunar surface far enough to uncover an ancient mountain range.

D) The crater was formed by impact, but it has penetrated into the lunar surface far enough to evoke lava flow, which has produced a volcanic cone.

181. What are the MOST common shapes of lunar craters, and why?

A) all shapes from round to oval, depending on the angle at which the projectile hit the surface

B) round because most of the craters formed from volcanic explosions, not meteoric impacts

C) random shapes because mantle convection has deformed the surface and distorted the craters

D) round because the incoming projectile vaporized and exploded to form the crater

182. Why does the ejecta blanket around some lunar craters appear light-colored?

A) These craters are relatively young and have not yet been contaminated and made darker by incoming material.

B) The impact punched through the lunar crust and released lighter magma from the Moon’s molten mantle.

C) The craters are relatively old.

D) The incoming projectile was composed of lighter material and colored the Moon’s surface.

183. What is a mare on the Moon?

A) large area of darker material on the lunar surface

B) sinuous valley, generally caused by the collapse of an old lava tube

C) horse-shaped region of darker material

D) large area of lighter material on the lunar surface

184. Maria on the Moon are

A) ancient riverbeds, now dry.

B) uplifted regions surrounding large volcanoes.

C) heavily cratered highland regions.

D) ancient lava floodplains.

185. What is a mare on the Moon?

A) smooth floor of an ancient asteroid impact basin, never subjected to inundation by lava or other volcanic activity

B) large area smoothed by deformation and tectonic activity

C) large area of heavily cratered highland terrain

D) very large, ancient lava flow

186. What is the MOST likely cause of the smooth and relatively crater-free surfaces of lunar maria?

A) Volcanic ash rained on the surfaces of the basins in recent geological times, covering previous craters.

B) The lava in these basins flowed in the relatively late geological history of the Moon, after the period of major bombardment.

C) Dust storms had eroded and smoothed the surface earlier in the Moon’s history.

D) Smoother sediments were left behind after water had flowed into the basins and evaporated away.

187. The lunar maria appear smooth because they are

A) regions where craters have been obliterated by crustal deformation caused by hot spots and volcanic lava flow from the underlying molten mantle.

B) recent lava flows, occurring within the last billion years, that have obliterated earlier craters.

C) ancient lava flows that occurred soon after the end of an early period of intense bombardment and that have had relatively few impacts since then.

D) ancient sea beds, now dry, dating back to when the Moon had a denser atmosphere and rainfall was abundant.

188. What is the distribution of maria on the Moon’s surface?

A) Maria are largely confined to the hemisphere facing Earth; there are only a few small maria on the distant side.

B) Maria are distributed uniformly over the Moon’s surface, as expected from random bombardment by debris from space.

C) There are only a few large maria on the Earth-facing side of the Moon but many smaller maria on the far side.

D) The large maria seen on the Earth-facing side of the Moon are matched by equivalent maria at diametrically opposite positions on the Moon, but only the near side has small maria.

189. The highlands ringing Mare Imbrium are a typical lunar mountain chain. How is it believed they were formed?

A) by shrinkage of the crust as the Moon cooled

B) by impact

C) at a convergent boundary between lunar tectonic plates

D) by volcanism

190. How do the near and far sides of the Moon compare?

A) Both sides are quite similar to each other—each side has several large mare, or “seas,” surrounded by heavily cratered terrain.

B) The near side has extensive, heavily cratered regions between and around the smooth maria, or “seas,” whereas the far side is almost entirely covered with maria.

C) It is not known; the far side is hidden in perpetual darkness.

D) The near side has several large maria, or “seas,” whereas the far side has only a few small maria.

191. Compared to the Earth-facing side, the side of the Moon that faces away from Earth has

A) fewer craters.

B) larger maria.

C) a higher average elevation.

D) a thinner crust.

192. The appearance of the entire surface of the Moon could be described as

A) uniform distribution of surface features, including maria and craters.

B) maria only on the near side, no major maria on the far side.

C) dry, waterless terrain on the near side, ice sheets on the dark side.

D) mostly craters on the near side, extensive maria and few craters on the far side.

193. When observers see a full Moon, there is a back side that they do not see. Which one of these statements about this situation is true?

A) This far side looks very similar to the near side.

B) When observers see a new Moon, they are seeing this far side.

C) If an astronaut was standing in the middle of this far side, they would never see Earth.

D) If an astronaut was standing in the middle of this far side, they would never see the Sun.

194. Examination of the whole surface of the Moon shows that

A) there are two distinctly different sides, the side seen from Earth and the side hidden from Earth.

B) craters exist only on one side of the Moon.

C) there are no differences in surface features around the whole Moon.

D) the northern hemisphere is distinctly different from the southern hemisphere.

195. The near and far sides of the Moon are particularly different, as seen by the fact that the

A) average height of the overall terrain is much lower on the far side.

B) far side has no large maria.

C) far side is always in darkness.

D) number of craters differs markedly, with fewer on the far side.

196. Major maria on the Moon exist

A) uniformly over the surface.

B) only on the Earth-facing side.

C) only in a band close to the equator.

D) only in the northern hemisphere.

197. Which of these statements is NOT true of the Moon?

A) Almost all craters on the Moon have been made by meteoroid impacts.

B) There are extensive lava floodplains on both the near and the far sides of the Moon.

C) There are large basins on the Moon that were carved out by asteroid impacts.

D) There are highly cratered regions on both the near and the far sides of the Moon.

198. The smooth, dark maria on the Moon are

A) immense basins that are smooth because they were covered by lava flows after the early heavy bombardment had ended.

B) immense impact basins that are smooth because earlier craters were wiped out by the impact.

C) areas that were still molten at the time of the early heavy bombardment and therefore show no evidence of the impacts.

D) regions that, although as old as the cratered highlands, escaped the early heavy bombardment.

199. The smooth surfaces of the lunar maria were MOST likely caused by

A) lava flows in the early history of the Moon.

B) dust storms that smoothed and covered the surface.

C) volcanic ash that rained on the surfaces of the basins in ancient times.

D) water flowing into the basins and allowing sediments to settle over their surfaces.

200. What is the name of a long, winding crack in a lunar mare?

A) rille

B) caldera

C) rift zone

D) regolith

201. What is a lunar rille?

A) long, winding crack in the surface of a mare

B) long, curved mountain range

C) large crater with a central peak

D) deep trench between two tectonic plates

202. Lunar rilles are

A) large irregular lava basins.

B) central peaks of lunar craters.

C) meandering, canyonlike valleys.

D) bright streaks radiating from large impact craters.

203. A rille is a

A) pattern seen in the tail of a comet.

B) type of geological fault on Venus.

C) meandering canyon on Mars.

D) shallow winding valley on the Moon.

204. Where in the universe would one look for a rille?

A) on Mars because rilles are the “canals” seen by Lowell to extend across the planet surface

B) in the galactic plane because it is a dark dust band

C) in Saturn’s rings because rilles are the gaps in the rings

D) on the Moon because it is the name given to a deep winding canyon there

205. The older, lighter-colored, and heavily cratered highlands take up _____ of the total lunar surface.

A) more than 4/5

B) less than 1/5

C) between 1/3 and 1/2

D) between 1/2 and 3/4

206. The smooth, dark maria take up what fraction of the entire surface of the Moon?

A) between 1/3 and 1/2

B) more than 4/5

C) less than 1/5

D) between 1/2 and 3/4

Section: 7-6

207. How many times have human beings landed on the Moon?

A) 4 times

B) 6 times

C) 7 times

D) 5 times

208. The human exploration of the surface of the Moon during the Apollo program lasted

A) less than a year.

B) about 25 years.

C) about 10 years.

D) less than 4 years.

209. Which was the first spacecraft to land human beings on the Moon?

A) Apollo 13

B) Apollo 10

C) Soyuz 5

D) Apollo 11

210. The first successful Moon landing, by Apollo 11, placed astronauts on the Moon in

A) 1938.

B) 1969.

C) 1985.

D) 2000.

211. The type of rock of which the lunar maria are composed is

A) basalt.

B) limestone.

C) anorthosite.

D) granite.

212. Which of these kinds of materials is NOT found on the Moon?

A) basalt

B) anorthosite

C) limestone

D) regolith

213. What is anorthosite?

A) rock found on the low-lying lunar plains and also in Hawaii and Iceland

B) powdered rock, which covers the Moon’s surface like dust

C) an ancient rock that covers the lunar highlands

D) rocks created from scattered debris fused together under high temperature and pressure

214. The Apollo astronauts dated many types of lunar rocks. Which of these is the oldest?

A) anorthosite

B) Lava

C) impact breccia

D) mare basalt

215. What is the lunar regolith?

A) part of the lunar surface that is not covered with lava flows

B) lunar crust and mantle together

C) deeper part of the lunar crust that has not been extensively cracked by impacts

D) layer of fine powder covering the lunar surface

216. A regolith is a(n)

A) extremely large, isolated rock on the surface of a planet or other object.

B) lithospheric plate, moved slowly by geologic processes.

C) heavily cratered region on a planet or other object.

D) layer of pulverized rock on the surface of a planet or other object.

217. One feature discovered on the Moon is a cliff called a “scarp”. How do planetary scientists believe they were formed?

A) by shrinkage of the crust as the Moon cooled

B) by impact

C) at a convergent boundary between lunar tectonic plates

D) by volcanism

218. The surface of the Moon may be described as

A) eroded basalt held together by subsurface ice (permafrost).

B) regolith (pulverized rock) in and near craters and hard bedrock everywhere else.

C) hard bedrock almost everywhere because there is very little erosion on the Moon.

D) regolith (pulverized rock).

219. What name is given to the layer of fine powder and rock fragments that covers the lunar surface?

A) mantle

B) regolith

C) rille

D) mare

220. What process created the lunar regolith?

A) successive cracking and shattering of lunar rocks by very rapid and extreme temperature changes throughout the Moon’s history

B) cracking and pulverizing by meteoric bombardment

C) billions of years of the alternating freezing and thawing of subsurface water

D) continuous erosion by charged particles in the solar wind

221. The age of Moon rocks has been determined primarily by what method?

A) measurements of radioactive elements in the rocks

B) careful measurement of magnetic fields “frozen into” the lunar rocks

C) counting of the numbers of micrometeoroid craters on the rock surface

D) careful chemical analysis of the constituents

222. The age of the Moon is determined primarily by

A) measurements of radioactive elements and radioactive dating.

B) radiocarbon dating of remnants of living material such as plant life.

C) measurements of the relative concentrations of easily melted and evaporated substances, the “volatiles,” and the less volatile materials, the “refractory” elements.

D) careful crater counts over different regions of the Moon and comparison to known meteoroid densities in space.

223. Most surface rocks on Earth are younger than a few million years old, whereas ages of lunar rocks have been measured in billions of years. Why?

A) Much of Earth’s surface is continually recycled (created and subducted) by the underlying mantle because of plate tectonic activity; this process does not occur on the Moon.

B) Most early surface rocks on Earth have been washed into the sea by weathering and rainwater; this process does not happen on the Moon.

C) The complete surface of Earth has been covered periodically by younger material from intense volcanic eruptions in the last few million years; no such activity occurred on the Moon.

D) The ages of Earth and the Moon are fundamentally different; the Moon is an old object captured from space by a younger Earth.

224. How old are the lunar maria?

A) less than 1 billion years old

B) 4.0 to 4.3 billion years old

C) 3.1 to 3.8 billion years old

D) 1.8 to 2.6 billion years old

225. How old are the lunar highlands?

A) 4.0 to 4.3 billion years old

B) 3.1 to 3.8 billion years old

C) less than 1 billion years old

D) 1.8 to 2.6 billion years old

236. The oldest material found on the Moon during crewed and noncrewed exploration was

A) smooth, dark glass formed by meteoritic impact.

B) water ice locked into permafrost on the surface of the Moon.

C) anorthositic rocks from the highlands.

D) basalt rocks from the mare basins.

227. The type of rock that makes up the lunar highlands is

A) granite.

B) limestone.

C) anorthosite.

D) basalt.

228. Some evidence for water has recently been discovered on the Moon in the form of

A) ice in deep craters near the south pole, perpetually shaded from sunlight.

B) thin, hazy clouds overlaying the dark polar regions, where they are shaded from the Sun’s heat.

C) permafrost embedded in the centers of the large, dark maria, their darker color showing the presence of frost.

D) fluid water flowing in deep tunnels (some of which have collapsed to form rilles on the lunar surface), where it is protected from solar radiation.

229. What is the status of water on the Moon?

A) Water has not been found on the Moon in any form.

B) Water has not been found to exist at present on the Moon, but there is evidence that the Moon’s large maria once contained large seas.

C) Water ice has been found in craters near the Moon’s south pole.

D) There is subsurface water throughout more than half the Moon.

230. Spacecraft exploring the Moon in the 1990s found evidence of water

A) as frost on the rims of craters, frozen out during the lunar night but quickly evaporating when illuminated by sunlight.

B) in the depths of the sinuous rilles or valleys, probably the frozen remnants of the rivers that caused the valleys.

C) as ice in craters near the Moon’s south pole.

D) as permafrost all over the Moon, particularly in the light-colored highlands.

231. Several space probes have searched for evidence of water on the Moon. What have they concluded?

A) There is no water on the Moon, in ice or liquid form.

B) There is water ice near the Moon’s poles but no liquid water.

C) There is water ice near the Moon’s poles and evidence for rare liquid water flows on its surface.

D) The question of whether water ice exists on the Moon remains unanswered.

232. Which of these observations have been made about the Moon that will be very helpful (if they prove true) as humans begin to plan for its colonization?

A) discovery of evidence of water (as ice) that can be used for the support of life, the growth of food, and as fuel if it is split by sunlight into hydrogen and oxygen

B) its synchronous rotation, keeping one side opposite Earth at all times, simplifying communication with Earth stations

C) mapping of rilles that, as collapsed lava tunnels, indicate that intact tunnels may be found that will be useful as shelter for early settlers

D) discovery of coal, an essential source of fuel, in various locations

233. In 2010 the lunar orbiter Chandrayaan-1 discovered hydroxyl radicals and hydrogen in

A) the Moon’s atmosphere.

B) the regolith.

C) the basalt of Mare Tranquillitatis.

D) the rilles on the Moon’s far side.

234. The present understanding of the existence of water on the Moon is that there is

A) no water anywhere on the Moon.

B) water ice in sheltered craters near both poles.

C) water only in the regolith (in trace amounts).

D) water in the regolith and near the south pole.

235. Moonquakes

A) never occur; the Moon is seismically quiet.

B) occur but are much weaker and much less frequent than earthquakes.

C) are much more violent and occur much more often than earthquakes.

D) occur but only from the impact of meteoroids from space.

236. Mascons, or concentrations of high-density material detected by their effect on the orbits of spacecraft, appear to be coincident with which features on the Moon’s surface?

A) north and south polar regions that are never sunlit

B) new craters surrounded by radially aligned lighter markings

C) highest mountain ranges on the lunar surface

D) large maria

237. Which of these is NOT evidence that the Moon’s surface has changed in the relatively recent past?

A) wrinkle ridges

B) graben

C) maria

D) lunar domes

238. What do planetary scientists believe mascons to be?

A) solidified magma in the Moon’s maria

B) intact remnants of large asteroids buried in the Moon’s surface

C) protrusions from the Moon’s iron core

D) regions of the Moon’s crust that rebounded after large asteroid impacts

239. Long troughs at the edges of the Moon’s maria where parts of the surface have descended are

A) rilles.

B) wrinkle ridges.

C) graben.

D) mascons.

240. What is the origin of wrinkle ridges on the Moon?

A) They are the edges of impact craters.

B) They are caused by the core of the Moon cooling and shrinking.

C) They are collapsed lava tubes.

D) Their origin is unknown.

Section: 7-7

241. Which one of these four theories about the origin of the Moon is now believed to be correct?

A) Earth and the Moon formed together, already orbiting each other.

B) The Moon formed separately in a different part of the solar nebula and was later captured by Earth.

C) Earth was spinning so rapidly while still molten that a piece spun off to form the Moon.

D) A single large object or set of smaller objects crashed into Earth, and debris from the collision formed the Moon.

242. According to the collision-ejection theory, when was the Moon formed?

A) very early, before Earth’s interior differentiated

B) after the Late Heavy Bombardment

C) about 60 to 100 million years after the solar system began to form

D) within the past billion years

243. Which of these is the BEST explanation for the origin of the Moon?

A) The Moon was created in its orbit around Earth by the same process that produced Earth, namely the collision of planetesimals that had formed by condensation and accretion of gas and dust.

B) The Moon was created by the process described in (A) but at some other location in the solar system.

C) While Earth was semimolten early in its formation, a chunk of material was flung out of it. It went into orbit and evolved to become the Moon.

D) The Moon was created by the process described in (C) except that the ejection was caused by a large impact of some object or objects on Earth.

244. Which of these is believed to be the correct explanation for the origin of the Moon?

A) The Moon was formed elsewhere in the solar system (which is why its composition differs from that of Earth) and was later captured by Earth’s gravity.

B) Shortly after its formation, Earth was spinning so fast in its molten state that a large piece of material was thrown off, and this chunk coalesced to form the Moon—leaving the Pacific Ocean basin in the place where it was thrown off.

C) Earth and the Moon were formed separately at the same time, while in orbit around their common center of mass, by the accretion of planetesimals.

D) Earth was struck by a large planetesimal or planetesimals that caused material to be ejected. This material coalesced to form the Moon.

245. Which of these theories is now considered to be the MOST likely for the formation of the Moon?

A) fission theory, in which a passing planetesimal body pulled material out of the still-molten Earth and left it in orbit to form the present-day Moon

B) co-creation theory, in which Earth and the Moon were formed at the same time out of the same material

C) capture theory, in which Earth’s gravity drew the Moon into orbit around it

D) collision-ejection theory, where an interplanetary collision or collisions knocked material into orbit around Earth that eventually formed into the present-day Moon

246. Although it is not yet known precisely how the Moon formed, an important clue is provided by the fact that

A) unlike Earth, the Moon has essentially no atmosphere.

B) the hemisphere of the Moon facing Earth is different from the hemisphere facing away.

C) the Moon is heavily cratered.

D) Moon rocks and minerals have very similar isotopic compositions to those of Earth.

247. If the current theory of the formation of the Moon is correct, all but one of these statements about Earth before the Moon’s creation is true. Which one?

A) It was season-less.

B) Its mantle was significantly larger than it is at present.

C) Its iron core was significantly larger than it is at present.

D) Earth rotated faster than it does now.

248. Which one of these is a characteristic of the Moon?

A) Its isotopic abundances are nearly identical to those on Earth.

B) Its composition is similar to that of Earth, particularly the proportion of iron.

C) It has a strong magnetic field.

D) Its crust is thinner on the far side.

249. Why are there fewer maria on the far side of the Moon than on the near side?

A) Earth protected the near side of the Moon from the heavy bombardment that affected the far side. This bombardment obliterated the maria on that side.

B) When the Moon was molten, the heavier materials moved a bit more toward the near side, thus displacing the lighter materials that moved a bit more toward the far side. The far side thus developed a thicker crust, making it more difficult for magma to penetrate to the surface there and fill in the large craters to produce maria.

C) The early Moon showed signs of tectonic activity, allowing the maria to float around on the surface. Thus, the present distribution of maria is just happenstance.

D) The early Moon showed signs of tectonic activity, allowing the maria to float around on the surface. The present distribution is due to the dense maria (mascons) being attracted to Earth.

250. What is the central idea of the MOST compelling theory of the origin of the tilt in Earth’s rotation axis?

A) gravitational pull of the Moon’s mascons

B) influence of a star passing near the early solar system

C) impact of the Mars-sized body as it ejected the material that formed the Moon

D) random distribution of angular momentum in the primordial solar nebula

251. What is the MOST probable heat source that produced extensive, maybe even total, melting of the Moon at an early stage in its history?

A) nuclear fusion reactions occurring in its core

B) intense sunlight from the early and very active Sun

C) tidal flexing and distortion caused by its motion around Earth

D) the impact energy of meteoritic bombardment

252. What kinds of large-scale changes have occurred on the Moon in the last billion years?

A) none—the Moon is exactly as it was 1 billion years ago

B) tectonic activity

C) volcanic activity and large-scale lava flows

D) gentle sculpting of the landscape by constant meteoroid impact

253. During what part of the Moon’s life were most of the craters formed?

A) between about 800 million and 1.5 billion years after the Moon formed

B) during the first 800 million years

C) approximately evenly from when the Moon first formed until the present day

D) during the first 200 million years

254. What appears to be the “impact history” of cratering on the Moon?

A) more or less constant bombardment from the earliest times to the present

B) short periods of heavy bombardment alternating with long periods of light bombardment throughout the Moon’s life

C) heaviest bombardment when the Moon first formed, gradually decreasing to light bombardment today

D) early period of heavy bombardment, then very light bombardment to the present

255. Why do the maria have few craters in them?

A) The maria are ancient sea beds. During the heaviest bombardment they were filled with water, and the meteoroids were broken up by the water, doing little damage to the maria themselves.

B) The maria are surfaced with hard basalt. Impacts mostly bounce off or break apart without making a crater.

C) The basalt that fills the maria has a low melting temperature. An impact will melt it, and it flows immediately to obliterate the crater.

D) There has been relatively little cratering activity since the maria were formed.

256. By dating Moon rocks astronomers can determine the Moon’s age. How long ago did the Moon form?

A) The maria are about 3.8 billion years old, suggesting that the entire Moon was molten at that time, so that is its probable age.

B) The oldest rocks in the lunar highlands are about 4.3 billion years old, so that must be the age of the Moon.

C) Radioactive dating of Moon rocks brought back to Earth show that the Moon must be about 4.5 billion years old.

D) Because it cooled and solidified almost to its core, the Moon must be at least a billion years older than Earth. Its age, therefore, must be at least 5.5 billion years.

257. Which of these techniques is NOT used to establish the age of the Moon’s surface features?

A) radioactive dating of rocks

B) observation of the degree of darkening of ejecta blanket material by solar wind particle impacts

C) observation of the amount of natural erosion in the lunar mountains

D) counting the density of crater impacts on the surface

258. There are half a dozen large maria on the side of the Moon facing Earth and only one small mare on the far side. Which of these explanations is the MOST likely?

A) Earth’s larger mass attracted many heavy bombardment particles. Some of those that missed Earth hit the near side of the Moon.

B) Originally, there were probably as many large maria on the far side as on the near side, but subsequent bombardments erased most of them on the far side, while the near side was shielded from such bombardments by Earth’s presence.

C) It is believed that the Moon was formed elsewhere in the solar system, so astronomers have no clue to its very early history—including this asymmetry in the maria.

D) The crust on the far side is thicker (because of Earth’s pull on the Moon’s core), and thus it was more difficult for lava to flow into large craters on the far side.

Section: 7-8

259. How many times does the Moon rotate on its axis each time it orbits around Earth?

A) zero because the Moon does not rotate on its axis at all

B) exactly once

C) anywhere from to 1 times, depending on the time of year

D) Twice

260. In its orbit around Earth, the Moon

A) keeps the sunlit side toward Earth.

B) keeps the same side toward Earth.

C) keeps the same side toward the Sun.

D) rotates once every 24 hours to keep in step with Earth.

261. To observers on Earth, the Moon shows

A) only the sunlit side at all times.

B) the same side at all times.

C) its whole surface once per year as Earth moves around the Sun.

D) its whole surface once per month as it rotates once per orbit around Earth.

262. Because of librations astronomers are able to see around the limb of the Moon and are able to view 59% of its surface from Earth. What is one cause of this?

A) The Moon is not perfectly round.

B) Earth is not perfectly round.

C) The Moon does not rotate on its axis at a steady rate.

D) The Moon has an elliptical orbit.

263. Which of these is NOT a contributor to librations, the “nodding” back and forth of the Moon that allows observers on Earth to see more than half of it?

A) The Moon’s rotation axis is not perpendicular to its orbital plane.

B) The Moon’s orbit around Earth and the ecliptic are not the same plane.

C) The Moon is not always the same distance from Earth.

D) Earth does not move at a steady rate in its orbit about the Sun.

264. Which of these statements about the Moon is true?

A) One side of the Moon is always in darkness.

B) The Moon can never pass through Earth’s shadow.

C) The Moon does not rotate on its axis.

D) Earth can never be seen from one side of the Moon.

265. If astronauts were to set up a permanent settlement on the near side of the Moon, how many times each year would Earth rise and set as seen by a resident of this base?

A) 12 times each year

B) 13 times each year

C) never—Earth would remain essentially motionless in the sky

D) once each year

266. If astronauts were to set up a permanent settlement on the near side of the Moon, how often would the Sun rise and set as seen by a resident of this base?

A) never—the Sun would remain essentially motionless in the sky

B) 365 times each year

C) about once each month

D) once each year

267. How long is the time between sunrise and sunset on the Moon?

A) about 2 weeks

B) almost infinite because the Moon does not rotate about its axis with respect to the Sun

C) about 1 year

D) about one 24-hour day

268. If an observer were standing on the Moon with Earth in view, how much time would elapse between two successive “Earthrises?”

A) about 1 synodic month

B) about 1 sidereal month

C) essentially forever

D) about 1 day

269. Astronauts at a Moon base that can be seen from Earth will NEVER see

A) one side of Earth because the Moon revolves at the same rate as Earth rotates.

B) the stars moving through their sky because the Moon does not rotate.

C) Earthrise or Earthset.

D) sunrise or sunset because the Sun will always remain in their sky.

270. The Moon produces tidal disturbances on the oceans of Earth. In most places on Earth, there are

A) two equal high tides and one low tide per day.

B) two high and two low tides per day.

C) one high tide and one low tide per day.

D) one high tide and one low tide per month.

271. The highest tides on Earth’s oceans occur at

A) full Moon or new Moon.

B) any time, because they are driven by the action of winds in Earth’s atmosphere.

C) full Moon but not at new Moon.

D) quarter Moon.

272. The time between two consecutive high tides at most places on Earth

A) is almost exactly 12 hours.

B) is almost exactly 24 hours.

C) is slightly less than 12 hours.

D) is slightly more than 12 hours.

273. High tide at any location on Earth occurs when the Moon is

A) high in the sky.

B) just rising.

C) just setting.

D) not visible.

274. How many “tidal bulges” caused by the Moon’s gravity are there on Earth?

A) one, on the side of Earth facing (almost) directly toward the Moon

B) one, on the side of Earth facing away from the Moon

C) two, one facing (almost) directly toward the Moon and one facing (almost) directly away from the Moon

D) four, one facing (almost) directly toward the Moon and the other three at 90° intervals from the first one

275. Sometimes high tides are higher than at other times. What name is given to the highest high tides?

A) spring tides

B) neap tides

C) Yule tides

D) rip tides

276. Sometimes high tides are lower than at other times. What name is given to the lowest high tides?

A) rip tides

B) pep tides

C) spring tides

D) neap tides

277. What are spring tides?

A) any low tides

B) any high tides

C) high tides that are significantly lower than the average high tide

D) high tides that are significantly higher than the average high tide

278. Spring tides occur

A) once a day.

B) once a month, at full Moon.

C) twice a month, at full Moon and new Moon.

D) once a year, in springtime.

279. When do spring tides occur?

A) only when the Moon and the Sun line up on the same side of Earth, at new Moon

B) whenever the Earth-Moon line makes a 90° angle to the Earth-Sun line

C) whenever Earth, the Moon, and the Sun form a straight line, regardless of which side of Earth the Moon is on (i.e., at the times of full Moon and new Moon)

D) only when the Moon, Earth, and the Sun form a straight line, with the Moon on the opposite side of Earth from the Sun, at full Moon

280. When do neap tides occur?

A) only when the Moon and the Sun line up on the same side of Earth

B) whenever Earth, the Moon, and the Sun form a straight line, regardless of which side of Earth the Moon is on

C) only when the Moon, Earth, and the Sun form a straight line, with the Moon on the opposite side of Earth from the Sun

D) whenever the Earth-Moon line makes a 90° angle to the Earth-Sun line

281. Neap tides occur

A) twice a month, at full Moon and new Moon.

B) once a month, at new Moon.

C) once a month, at first quarter Moon.

D) twice a month, at first quarter Moon and third quarter Moon.

282. Suppose there is an exceptionally strong high tide (a spring tide) right now. Approximately how long will it be until an exceptionally weak tide (neap tide) occurs?

A) 6 hours

B) 1 week

C) 1 month

D) 1 year

283. A point on Earth is experiencing a high tide. Neglecting local influences of currents, bays, etc., about how long will it be until another high tide occurs at this location?

A) 11.5 hours

B) 12.5 hours

C) 23 hours

D) 25 hours

284. The water on the side of Earth that faces away from the Moon experiences

A) a high tide because the combination of Earth’s motion and the Moon’s gravity makes water move away from the Moon toward the far side of Earth.

B) no tidal force.

C) a low tide because all Earth’s water is pulled toward the side of Earth that faces the Moon.

D) either a high tide or a low tide, depending on the angle of the water to the Sun.

285. The reason for the alignment of the Moon with one face always toward Earth is that

A) sporadic (random) impact of meteoroids on the Moon has gradually slowed its rotation.

B) the Moon started spinning in this way as it was forming and has maintained this rotation.

C) tides due to gravitational forces from the Sun, while the Moon was molten, slowed the Moon’s rotation.

D) tides due to gravitational forces from Earth, while the Moon was molten, slowed the Moon’s rotation.

286. Why is the Moon in a synchronous orbit around Earth, always keeping the same face toward Earth?

A) There is a strong magnetic attraction between the two bodies that keeps the Moon turned toward Earth.

B) The Moon must rotate on its axis at the same rate it orbits Earth to conserve angular momentum.

C) As the Moon rotates, friction between the Moon’s large liquid interior and its mantle has slowed the rate of rotation until it just matches the orbital rate. Over time it will slow further, and then the Moon will no longer be in a synchronous orbit.

D) When the Moon was molten and experienced chemical differentiation, the gravitational pull of Earth caused large tides. The friction created as Earth’s gravity attempted to keep the high tide bulge pointed toward Earth resulted in the Moon’s rotation being slowed, causing it always to face Earth.

287. The Moon rotates synchronously as it orbits Earth, always keeping one side pointed toward Earth, because

A) of the effect of the magnetic field of Earth on the magnetic field of the Moon, much like the effect on a compass needle.

B) it had precisely this rate of spin, equal to its revolution period around Earth, when it was formed.

C) of frictional effects from micrometeoroids in its orbital plane, especially early in its history.

D) of the effect of the gravitational pull of Earth on the tidally induced bulge on the Moon.

288. The reason that the Moon always keeps one face toward Earth is that

A) the Moon was spinning in this way when it was formed, and it has since maintained this rotation.

B) gravitational forces from Earth act on the tidal bulge of the Moon.

C) impacts of asteroids on the Moon early in its history slowed its rotation rate.

D) gravitational forces from the Sun act on the tidal bulge of the Moon.

289. Moonquakes occur MOST often when the Moon is near perigee (at its closest approach to Earth). The reason is

A) increased tidal distortion of the Moon by Earth.

B) higher probability of impacts on the Moon of meteoroids that have been accelerated by Earth at these lunar phases.

C) increased speed of rotation of the Moon at these times and consequent reduction of the gravitational force on the surface.

D) increased sunlight on the Moon’s surface at these times.

290. Looking down on the North Pole of Earth, the high tide bulges of Earth’s oceans are

A) exactly along the line defined by the center of Earth and the center of the Moon.

B) exactly along the line defined by the center of Earth and the center of the Sun.

C) east and west of the line defined in (A) with the bulge nearer the Moon being east of this line.

D) east and west of the line defined in (A) with the bulge nearer the Moon being west of this line.

291. Does Earth’s gravity raise tides on the Moon today?

A) No. The Moon has now moved beyond the reach of Earth’s gravity.

B) No. Since the Moon is now in a synchronous orbit, Earth’s gravity can no longer raise tides.

C) Yes. Tides can be raised in the molten core (if it exists) and in the plastic mantle.

D) Yes. In fact, it is the monthly deformation of the Moon’s shape by tides that allows observation of more than 50% of the Moon’s surface.

292. All of these might be consequences of Earth being formed without its Moon EXCEPT

A) very large tides.

B) very strong winds.

C) very large waves.

D) a shorter day.

Section: 7-9

293. The Moon is being pulled forward by Earth’s tidal bulge. What motion results from this?

A) The pull increases the Moon’s energy, causing it to move into a more distant orbit where it moves more slowly.

B) The pull increases the Moon’s energy, causing it to move into a more distant orbit where it moves more rapidly.

C) The pull increases the speed of the Moon. This places it in an orbit closer to Earth as required by Kepler’s third law.

D) The pull decreases the speed of the Moon. This places it in an orbit farther from Earth, as required by Kepler’s third law.

294. Which of these describes the dynamics of the Earth-Moon system?

A) Earth’s rotation is speeding up, whereas the Moon is moving slowly outward away from Earth.

B) Earth’s rotation is slowing down, whereas the Moon is moving slowly outward away from Earth.

C) Earth’s rotation is speeding up, whereas the Moon is moving slowly toward Earth.

D) Earth’s rotation is slowing down, whereas the Moon is slowly approaching Earth by spiraling inward.

295. How quickly is the Moon spiraling away from Earth?

A) a few centimeters per million years

B) The Moon is not moving away from Earth because its orbit is governed by Newton’s laws.

C) a few centimeters per century

D) a few centimeters per year

296. The Moon is spiraling slowly away from Earth. What is the future of this motion?

A) The Moon will continue moving away from Earth forever, although the rate of recession will slow constantly.

B) The Moon will continue moving away from Earth forever, and the rate of recession will increase slowly.

C) When the Moon gets far enough from Earth it will become more influenced by the Sun and will eventually become a planet in a solar orbit.

D) As the Moon is receding from Earth, Earth’s rate of rotation is slowing. It will eventually become tidally locked in synchronous motion with the Moon. At that point the tidal bulges will be along the Earth-Moon line, and there will be no more force to increase the Moon’s orbit.

297. How does the speed of Earth’s tectonic plates compare with the speed at which the Moon is receding from Earth?

A) They are comparable in size.

B) Continental drift is many orders of magnitude larger than the Moon’s drift speed.

C) The Moon’s drift speed is many orders of magnitude larger than continental drift.

D) It is not possible to compare because the speed of the Moon’s recession has never been measured.

298. Which of these statements is a correct description of the Moon’s orbit?

A) The Moon is gradually spiraling away from Earth.

B) The Moon’s distance from Earth increases and decreases cyclically once every 26,000 years.

C) The Moon is gradually spiraling toward Earth.

D) The Moon’s distance from Earth remains constant from year to year, on average.

299. Earth rotates eastward, dragging eastward the tidal bulge raised by the Moon. Suppose the Moon rotated westward around Earth, rather than eastward. How would the dynamics of the Earth-Moon system be affected?

A) The Earth-Moon system would not be affected. The Moon would spiral inward toward Earth, as it does now.

B) The Earth-Moon system would not be affected. The Moon would spiral outward away from Earth, as it does now.

C) The drift of the Moon would be reversed. It would spiral away from Earth instead of toward it.

D) The drift of the Moon would be reversed. It would spiral toward Earth instead of away from it.

300. The Moon, because of the tides in Earth’s oceans, is

A) spiraling outward, away from Earth.

B) shrinking.

C) unaffected and continues to orbit in a constant elliptical path.

D) moving slowly toward Earth.

301. The Moon is getting farther from Earth. Will this continue forever?

A) Yes. The Moon will always drift away from Earth.

B) No. When Earth’s rotation slows to zero (because of tidal friction), the recession will end.

C) No. When Earth’s rotation slows to match the motion of the Moon (synchronous rotation), the recession will end.

D) No. Earth’s rotation will slow to a stop and then reverse direction. At that point the Moon will begin to move closer to Earth again.

302. Which of these statements is a correct description of the rotation of Earth?

A) The average length of a day is gradually getting longer because Earth’s rate of rotation is slowing down.

B) The average length of a day varies unpredictably from one year to the next because of the combined effects of solar and lunar tides.

C) The average length of a day is gradually getting shorter because Earth’s rate of rotation is speeding up.

D) The average length of a day is constant from year to year because nothing can change the speed of rotation of Earth.

303. Two hundred million years ago, during the dinosaur period on Earth, the Moon was

A) at the same distance from Earth it is now, and the day (on Earth) was the same length it is now.

B) farther away from Earth than it is now, and an Earth day was longer.

C) closer to Earth than it is now, and an Earth day was longer.

D) closer to Earth than it is now, and an Earth day was shorter.

304. One effect of the tidal drag of the ocean waters on Earth is

A) tilting of its spin axis farther and farther away from the perpendicular to the ecliptic.

B) slowing down of its spin rate.

C) speeding up of its rate of spin, thereby gaining energy from the Moon’s orbital motion.

D) speeding up of its orbital motion around the Sun.

305. Which of these statements was NOT true just after Earth and the Moon were formed?

A) Earth was spinning much faster than it is now.

B) The Moon was much closer to Earth than it is now.

C) The tides were many times as severe as they are at present.

D) There were no seasons.