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11/20/2016 Chapter 7 Homework Chapter 7 Homework Due: 11:59pm on Sunday, September 25, 2016 To understand how points are awarded, read the Grading Policy for this assignment. Question 1 Part A Listed below are geographic features of the terrestrial worlds. In each case, identify the geological process: impact cratering, volcanism, erosion, or tectonics (where tectonics is any largescale processes affecting the structure of the planetary crust), most responsible for the feature described. Match the geographic feature to the appropriate geologic process. Hint 1. Are tall volcanoes required for volcanism? ANSWER: only the building of tall volcanoes. Volcanism refers to the building of tall volcanoes and any subsequent lava flows that come from them. any flow of molten lava across a surface. Hint 2. How can you distinguish impact craters from volcanic craters? Which of the following would tell you that craters you are observing were formed by impacts rather than volcanism? ANSWER: The craters are circular. The craters have smooth bottoms indicating that lava flowed in them. The craters are not associated with any mountains or lava flows. Hint 3. What is tectonics? The geological process that we call tectonics refers to __________. ANSWER: any surface disruption, such as stretching or crumpling, caused by stresses within the interior of the world only surface changes, such as the movement of continents, caused by the motion of plates around the world’s surface the surface features that we see when a world has been heavily bombarded by impacts Hint 4. What is required for erosion? Which of the following is necessary for erosion to occur on a planet or moon? ANSWER: liquid water an atmosphere lava flows both liquid water and an atmosphere both liquid water and lava flows Hint 5. What is Valles Marineris? ANSWER: https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 1/12 11/20/2016 Chapter 7 Homework Valles Marineris is a giant mountain on Mars. a system of driedup rivers on Mars. a long system of canyons stretching nearly a fifth of the way around Mars, looking much like a set of giant cracks in the surface. Hint 6. What is Olympus Mons? ANSWER: Olympus Mons is a giant mountain on Mars, with a crater at its top. a huge impact crater on Mars. a long system of canyons stretching nearly a fifth of the way around Mars, looking much like a set of giant cracks in the surface. Hint 7. How did Mercury’s cliffs form? ANSWER: Mercury was bombarded by impacts. Mercury’s long, tall cliffs are thought to have formed when the entire planet shrank, causing the surface to crumple. water gushed through canyons and left great walls exposed as cliffs. Hint 8. What surface features do we see in the lunar highlands? ANSWER: giant volcanoes. The major surface features of the lunar highlands are craters. smooth plateaus that must once have been flooded by lava. ANSWER: https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 2/12 11/20/2016 Chapter 7 Homework Correct Remember that the four processes are interrelated, so although one may be most important to a particular feature, others often also play a role. For example, some erosion has occurred on the volcanic island of Hawaii, there are impact craters on the slopes of Olympus Mons, and volcanism and tectonics almost always go handinhand. Question 2 Choose the best answer. Part A Which heat source continues to contribute to Earth’s internal heat? ANSWER: accretion radioactive decay sunlight Correct Question 3 Choose the best answer. Part A Which of a planet's fundamental properties has the greatest effect on its level of volcanic and tectonic activity? ANSWER: size distance from the Sun rotation rate Correct Question 4 Choose the best answer. Part A What do we conclude if a planet has few impact craters of any size? ANSWER: The planet was never bombarded by asteroids or comets. Its atmosphere stopped impactors of all sizes. Other geological processes have wiped out craters. Correct https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 3/12 11/20/2016 Chapter 7 Homework Question 5 Part A The processes responsible for virtually all surface geology are _________. ANSWER: impact cratering, volcanisms, tectonics, and erosion accretion, differentiation, and radioactive decay convection, conduction, and radiation eruptions, lava flows, and outgassing Correct Question 6 Part A Which of the following is the most basic definition of a greenhouse gas? ANSWER: a gas that reflects a lot of sunlight a gas that makes a planet much hotter than it would be otherwise, even in small amounts a gas that absorbs infrared light a gas that keeps warms air from rising, and therefore warms the surface Correct Question 7 Part A What observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius? ANSWER: Mercury's unusually high density the presence of many long, tall cliffs the presence of many impact craters the characteristics of the Caloris Basin Correct Question 8 First, launch the animation below. Explore the interactive photo before beginning to answer the questions. Be sure you have clicked the “Show labels” button. https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 4/12 11/20/2016 Chapter 7 Homework Part A Assuming that features you see on Mars are similar to features found on Earth, what would a casual inspection of the interactive photo of Mars lead you to suspect about water on Mars? Hint 1. How many rivers, lakes, and seas are visible in the photo of Mars? True or False? Many examples of presentday rivers, lakes, and seas are plainly visible in the photo of Mars. ANSWER: True False Hint 2. What features are visible at Mars’s north and south poles? True or False? Polar caps are plainly visible at Mars’s poles, suggesting the presence of frozen water there. ANSWER: True False ANSWER: Abundant surface water is found in large, brownish pools inside craters. There are numerous small streams flowing with water. Surface water only exists as frozen ice. No surface water currently exists in any form. Correct There is nothing on the brownish surface to suggest liquid water, and closeup photos confirm that there is no liquid water on Mars today. However, the prominent polar caps look much like Earth’s polar caps, and would therefore make you suspect that they are made of water ice. In fact, they contain both frozen carbon dioxide and frozen water. Part B Which of the following Mars surface features provides dramatic evidence that volcanism has played a role in shaping the surface of Mars? Hint 1. What surface features are signs of past volcanic activity on terrestrial planets? True or False? The presence of either volcanoes or large lava plains indicates past volcanic activity on a terrestrial planet. ANSWER: https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 5/12 11/20/2016 Chapter 7 Homework True False Hint 2. Do craters always indicate past volcanic activity? True or False? The presence of craters is always a sign of past volcanic activity. ANSWER: True False ANSWER: the polar caps the southern highlands Valles Marineris Olympus Mons Correct Olympus Mons is a very large shield volcano. You can also see numerous other volcanoes on Mars, including three large ones on the Tharsis bulge. Part C When you zoom in on the section labeled “Southern Highlands,” which geologic processes are most clearly evident? Hint 1. What surface features are prominent in the southern highlands? True or False? A great many craters are present in the southern highlands. ANSWER: True False Hint 2. Are all of the surface features in the southern highlands equally distinct? True or False? Of the craters seen in the southern highlands, some have features that are more crisp and distinct than others. ANSWER: True False ANSWER: volcanism and erosion impact cratering and erosion impact cratering and volcanism tectonics and erosion volcanism and tectonics https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 6/12 11/20/2016 Chapter 7 Homework Correct The most obvious features of the southern highlands are the many impact craters, but a close examination shows that many of them have been “smoothed out,” indicating erosion that has occurred over time. Question 9 Part A What do we mean by a runaway greenhouse effect? ANSWER: a greenhouse effect that starts on a planet but later disappears as gases are lost to space a greenhouse effect that heats a planet so much that its surface rock melts a process that heats a planet like a greenhouse effect, but that involves a completely different mechanism of heating that doesn't actually involve greenhouse gases a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere Correct Question 10 Learning Goal: To use your understanding of the terrestrial planets in our solar system to predict properties of terrestrial planets in other solar systems. Introduction. The diagram shows the size, orbital distance, and rotation rate of a hypothetical planet around another star, which we'll call Planet Z. Assume that Planet Z is a terrestrial planet shaped by the same basic processes that shape the terrestrial planets of our solar system and that it orbits a star of the same type and age as the Sun. Part A Based on Planet Z's size, orbital distance, and rotation rate, which of the following properties is it likely to have? https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 7/12 11/20/2016 Chapter 7 Homework Check all that apply. Hint 1. How does size affect the characteristics of a terrestrial world? Large terrestrial worlds __________ than smaller terrestrial worlds. ANSWER: have higher surface temperatures retain internal heat longer have more erosion Hint 2. How does orbital distance affect the characteristics of a terrestrial world? Terrestrial worlds that are close to their star tend to have __________ than terrestrial worlds that are farther away. ANSWER: more erosion higher surface temperatures thicker atmospheres Hint 3. How does rotation rate affect the characteristics of a terrestrial world? Relatively rapid rotation is required for a world to have __________. ANSWER: an atmosphere active volcanoes strong winds and violent storms ANSWER: erosion due to liquid water strong winds and violent storms an atmosphere produced by outgassing seasons active volcanoes a surface crowded with impact craters polar ice caps active tectonics Correct Continue on to explore why the planet has these characteristics. Part B You have found that Planet Z should have active tectonics and volcanism and an atmosphere produced by volcanic outgassing. What single factor explains why the planet should have these characteristics? Hint 1. How does size affect the characteristics of a terrestrial world? Large terrestrial worlds __________ than smaller terrestrial worlds. ANSWER: https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 8/12 11/20/2016 Chapter 7 Homework retain internal heat longer have more erosion have higher surface temperatures Hint 2. How does orbital distance affect the characteristics of a terrestrial world? Terrestrial worlds that are close to their star tend to have __________ than terrestrial worlds that are farther away. ANSWER: higher surface temperatures thicker atmospheres more erosion Hint 3. How does rotation rate affect the characteristics of a terrestrial world? Relatively rapid rotation is required for a world to have __________. ANSWER: active volcanoes an atmosphere violent weather and storms ANSWER: has a slow rotation rate. Planet Z closely orbits its star. lacks axis tilt. has a large size for a terrestrial planet. Correct Large size means more internal heat. This internal heat drives active tectonics and volcanism, which is the source of outgassing. Part C In Part A, you found that Planet Z should not have polar ice caps or liquid water. What single change to Planet Z's characteristics would allow it to have these things? Hint 1. How does size affect the characteristics of a terrestrial world? Large terrestrial worlds __________ than smaller terrestrial worlds. ANSWER: have higher surface temperatures have more erosion retain internal heat longer Hint 2. How does orbital distance affect the characteristics of a terrestrial world? Terrestrial worlds that are close to their star tend to have __________ than terrestrial worlds that are farther away. ANSWER: https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 9/12 11/20/2016 Chapter 7 Homework higher surface temperatures thicker atmospheres more erosion Hint 3. How does rotation rate affect the characteristics of a terrestrial world? Relatively rapid rotation is required for a world to have __________. ANSWER: active volcanoes an atmosphere violent weather and storms ANSWER: a smaller size a larger size a greater distance from its star a larger axis tilt Correct The planet is too hot for liquid water or ice, so moving it farther from its star would allow it to cool down. If it cooled enough—but not too much—it could have surface liquid water and ice caps. Part D In Part A, you found that Planet Z should not have strong winds and violent storms. What single change to Planet Z's characteristics would cause it to have strong winds and violent storms? Hint 1. What are the general requirements for strong winds and violent storms? If a planet has an atmosphere, the most important factor determining the strength of its surface winds is its __________. ANSWER: rotation rate distance from its star axis tilt ANSWER: a faster rotation rate a larger axis tilt a smaller size a greater distance from its star Correct The basic requirements for strong winds and violent storms are an atmosphere and relatively rapid rotation. An atmosphere is necessary to have wind of any type, while rotation is necessary to create the forces (in particular, the Coriolis force) that tend to drive winds on a planet's surface. Storms will be even stronger if there is also evaporation of surface water. https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 10/12 11/20/2016 Chapter 7 Homework Part E In Part A, you found that Planet Z should not have seasons. What single change to Planet Z's characteristics would cause it to have seasons? Hint 1. What causes seasons on Earth? The most important factor in the existence of seasons on Earth is Earth's __________. ANSWER: rotation rate distance from the Sun axis tilt ANSWER: a greater distance from its star a faster rotation rate a smaller size a larger axis tilt Correct Seasons are caused primarily by axis tilt, so a planet without axis tilt is not expected to have seasons (unless it has a highly elliptical orbit). Question 11 Choose the best answer. Part A The oxygen in Earth’s atmosphere was released by ANSWER: volcanic outgassing. the CO2 cycle. life. Correct Question 12 Part A What is the importance of the carbon dioxide (CO2) cycle? ANSWER: It will prevent us from suffering any consequences from global warming. It allows for an ultravioletabsorbing stratosphere. It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate. It makes the growth of continents possible. https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 11/12 11/20/2016 Chapter 7 Homework Correct Question 13 Part A Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by _____. ANSWER: human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere the increase in forest fires during recent years the human release of chemicals called CFCs into the stratosphere the fact that our politicians spout a lot of hot air Correct Question 14 Part A Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny? ANSWER: its distance from the Sun whether or not it has liquid water its size its composition Correct Score Summary: Your score on this assignment is 48.9%. You received 18.09 out of a possible total of 37 points. https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1646890 12/12