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Review Game Questions
1. What is differentiation in planetary geology?
2. Under what circumstances can differentiation occur in a planet?
3. The core, mantle, and crust of a planet are defined by differences in their
4. The lithosphere of a planet is the layer that consists of
5. What is the most important factor that determines the thickness, and therefore strength, of the
lithosphere?
6. Explain why the terrestrial planet cores contain mostly metal.
7. Which internal energy source is the most important in continuing to heat the terrestrial planets today?
8. Describe the process of convection.
9. Name the three principal sources of the internal heat of terrestrial planets.
10. The main process by which heat flows upward through the lithosphere is
11. Which two of the terrestrial planets have the thinnest lithospheres?
12. Explain why the smaller terrestrial worlds have cooler interiors than the larger ones.
13. Which of the terrestrial worlds has the strongest magnetic field?
14. Explain why the earth has the strongest magnetic field among the terrestrial worlds.
15. What is the most likely reason Venus does not have a strong magnetic field?
16. Which two properties are most important in determining the surface temperature of a planet?
17. What is tectonics?
18. What is erosion?
19. What is volcanism?
20. Describe the process of impact cratering.
21. How did the lunar maria form?
22. How do the size and chemical composition of a planet determine its internal temperature?
23. Why does the Moon have a layer of powdery "soil" on its surface?
24. What can we learn from the detailed shapes of craters?
25. The Caloris Basin on Mercury covers a large region of the planet, but few smaller craters have formed on
top of it. What does this tell us about when the Caloris Basin formed?
26. Describe the three sources of internal heat of the terrestrial planets.
27. Summarize some of the evidence suggesting that Mars once had flowing water.
28. Why do we think Mercury has so many tremendous cliffs?
29. What is Olympus Mons?
30. Why do we think Mercury contracted within about a billion years after it formed?
31. Explain how we can estimate the geological age of a planetary surface from its number of impact craters.
32. What is Valles Marineris?
33. What is the main visual difference between the lunar highlands and the lunar maria? What are the
implications of this observation?
34. The polar caps on Mars are composed of
35. Which two geological processes appear to have been most important in shaping the present surface of
Venus?
36. What process has shaped Earth's surface more than any other?
37. Why are there fewer large craters on the seafloor than on the continents?
38. How does seafloor crust differ from continental crust?
39. Describe the evidence for continental drift on Earth.
40. What drives the motion of the continental plates on Earth?
41. Ridges in the middle of the ocean are places where
42. Deep trenches in the ocean mark places where
43. The Hawaiian Islands formed as the result of plumes of hot mantle rising within a plate, called a
________________.
44. Arrange the terrestrial planets and the Moon in terms of increasing size. Contrast their surface features
and internal structure, paying particular attention to whether the object is geologically dead or active. Why
should the smaller planets be inactive and the largest still be geologically very active?
45. Describe the three sources of internal heat of the terrestrial planets?
46. What is the primary source of erosion on the Moon? Why does change there take so long?
47. Relate lunar rilles to volcanism on the Moon.
48. Describe several features on the earth's crust explained by plate tectonics.
Review Game Answers
1. the process by which gravity separates materials according to density
2. The planet must have a molten interior.
3. composition.
4. the rigid rocky material of the crust and uppermost portion of the mantle.
5. internal temperature
6. metals sank to the center during a time when the interiors were molten throughout.
7. radioactivity
8. It is the process in which warm material expands and rises while cool material contracts and falls.
9. accretion, differentiation, and radioactivity.
10. conduction.
11. Earth and Venus
12. They have relatively more surface area compared to their volumes.
13. Earth
14. It is the only one that has both a partially molten metallic core and reasonably rapid rotation.
15. Its rotation is too slow.
16. distance from the Sun and atmosphere
17. the disruption of a planet's surface by internal stresses
18. the wearing down or building up of geological features by wind, water, ice, and other phenomena of
planetary weather
19. the eruption of molten rock from a planet's interior to its surface
20. the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
21. Large impacts fractured the Moon's lithosphere, allowing lava to fill the impact basins.
22. Size is the most important factor in determining how rapidly a planet loses its internal heat. The
larger a planet is, the deeper is the "insulation" that surrounds the core and keeps in the heat. The
chemical composition of a planet determines the amount of radioactive elements present. Currently the
terrestrial planets' primary source of heat is radioactivity.
23. It's the result of gradual erosion by micrometeorites striking the Moon.
24. The shapes of craters can tell us the type of terrain in which they formed and whether they have been
subject to erosion. Craters that form in rocky surfaces usually have a simple bowl shape. Craters that
form in icy ground may look as if they formed in mud. Craters that lack sharp rims and bowl-shaped
floors have probably been reshaped over time by erosion.
25. the Caloris Basin formed toward the end of the solar system's period of heavy bombardment.
26. Accretion is heat generated by the agglomeration of planetesimals when the planet was formed.
Differentiation is heat generated by the energy released as dense objects fall toward the center of a planet
during the formation of the core of a planet. Radioactive decay generates heat by releasing nuclear energy
when an unstable (radioactive) isotope decays into a more stable element.
27. It has what looks like dried-up riverbeds and impact craters that appear to have formed in mud; the
Mars Pathfinder found rocks of many different types jumbled together, as would occur if there had once
been a great flood in the region; some very old craters appear to have been eroded by rain.
28. They were probably formed by tectonic stresses when the entire planet shrank as its core cooled.
29. shield volcano on Mars.
30. The surface of Mercury is marked by long, high cliffs. Such features result from tectonic compression,
but there are no corresponding features due to tectonic stretching. This suggests the whole planet
contracted as it rapidly cooled in its early history. We can date the contraction from the age of the
volcanic flows on its surface: volcanic (and all geologic) activity probably came to an abrupt halt as a
result of the planet's contraction.
31. Even though impacts still occur today, the vast majority of craters formed during the bombardment
period that ended around 3.8 billion years ago. A surface region that is still saturated with craters must
have remained essentially undisturbed for the last 3.8 billion years. In contrast, a surface region that has
few craters indicates that the original craters must have been somehow "erased" since then.
32. large canyon on Mars.
33. The lunar highlands are very heavily cratered and the lunar maria are generally smooth. (More
specifically, the maria contain only 3 percent as many craters per unit area as the highlands.) The
difference in the amount of craters shows that the maria formed after the highlands, at the end of the
heavy bombardment phase of the solar system. Radiometric dating of rocks from the highlands and maria
shows that the heavy bombardment phase lasted no longer than a few hundred million years.
34. mostly solid carbon dioxide and some water ice.
35. volcanoes and tectonics
36. plate tectonics
37. The seafloor crust is younger than the continental crust.
38. Seafloor crust is thinner, younger, and higher in density.
39. similar rocks and fossils are found in different continents
some continental boundaries fit together like pieces of a jigsaw puzzle
high ocean ridges between the continents
40. convection cells in the mantle
41. hot mantle material rises upward and spreads sideways, pushing the plates apart.
42. one plate slides under another, returning older crust to the mantle.
43. hot spot
44. Smallest: Moon: Ancient surface, heavy impact cratering, geologically dead.
Mercury: Ancient surface, heavy impact cratering, geologically dead.
Mars: Old surface, some impact cratering, geologically somewhat active.
Venus: Fairly new surface, a few impact craters, geologically active.
Largest: Earth: New surface, almost no impact craters, geologically active, features quickly eroded.
The smallest planets cooled quickly, and so lost their geological activity.
45. Accretion is heat generated by the agglomeration of planetesimals when the planet was formed.
Differentiation is heat generated by the energy released as dense objects fall toward the center of a planet
during the formation of the core of a planet. Radioactive decay generates heat by releasing nuclear energy
when an unstable (radioactive) isotope decays into a more stable element.
46. A constant fall of meteoroids from space pelts the moon, pulverizing the surface with tiny craters.
But really big impacts are rare, and these microscopic changes take a long time to show up as seen from
Earth. Our erosive agents like wind, water, and ice can make much more dramatic changes in short
periods of time, such as floods, sandstorms, glaciers, etc.
47. The rilles are ditches left by sinuous lava flows that run for many miles across the lunar surface. They
appear to be younger than the more extensive mare basalt flows.
48. Mountain ranges, volcanic mountain chains, mid-ocean rifts, oceanic trenches, faults, earthquakes,
and plate motion.