Astronomy 207 Midterm 4 - UofC Exam Actual Questions and Answers Verified 100% Correct 2026.

Astronomy 207 Midterm 4 - UofC Exam Actual Questions and Answers Verified 100% Correct 2026. How fast do plates move on Earth? A) a few centimeters per year B) a few millimeters per century C) a few kilometers per century D) quite fast, but only during earthquakes E) about 1 mile per hour - ANSWER -A) a few centimeters per year Ridges in the middle of the ocean are places where A) one plate slides under another, returning older crust to the mantle. B) hot mantle material rises upward, creating volcanic islands. C) hot mantle material rises upward and spreads sideways, pushing the plates apart. D) plates push together, creating ocean mountain chains. E) plates slip sideways relative to one another. - ANSWER -C) hot mantle material rises upward and spreads sideways, pushing the plates apart. Deep trenches in the ocean mark places where A) one plate slides under another, returning the older crust to the mantle. B) plates pull apart, leaving great rifts in the crust. C) hot mantle material rises upward and spreads sideways, pushing the plates apart. D) plates push together, creating ocean mountain chains. E) plates slip sideways relative to one another. - ANSWER -E) plates slip sideways relative to one another. How does seafloor crust differ from continental crust? A) Seafloor crust is thicker, older, and higher in density. B) Seafloor crust is thinner, younger, and higher in density. C) Seafloor crust is thinner, older, and lower in density. D) Seafloor crust is thicker, older, and lower in density. E) Seafloor crust is thicker, younger, and lower in density. - ANSWER -B) Seafloor crust is thinner, younger, and higher in density. Which of the following regions was the result of plumes of hot mantle rising in a hot spot within a plate? A) Alaska's Aleutian Islands B) Japan and the Philippines C) the islands of Hawaii D) the volcano Mount St. Helens E) all of the above - ANSWER -C) the islands of Hawaii Why are there fewer large impact craters on Earth's seafloor than on the continents? a) The oceans slow large impactors and prevent them from making craters. b) Erosion erases impact craters must faster on the ocean bottom than on land. c) Most impacts occur on the land. d) Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts. - ANSWER -d) Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts. How does the greenhouse effect work? A) Greenhouse gases transmit visible light, allowing it to heat the surface, but then absorb infrared light from Earth, trapping the heat near the surface. B) The higher pressure of the thick atmosphere at lower altitudes traps heat in more effectively. C) Ozone transmits visible light, allowing it to heat the surface, but then absorbs most of the infrared heat, trapping the heat near the surface. D) Greenhouse gases absorb X rays and ultraviolet light from the Sun, which then heat the atmosphere and the surface. E) Greenhouse gases absorb infrared light from the Sun, which then heats the atmosphere and the surface. - ANSWER -A) Greenhouse gases transmit visible light, allowing it to heat the surface, but then absorb infrared light from Earth, trapping the heat near the surface. Suppose Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be A) 250 K, which is well below freezing. B) 273 K, or about the freezing point for water. C) 283 K, or about 5 K cooler than it is now. D) 288 K, or about the same as it is now. E) 293 K, or about 5 K warmer than it is now. - ANSWER -A) 250 K, which is well below freezing. Heat escapes from a planet's surface into space by thermal radiation. Planets radiate almost entirely in the wavelength range of the A) infrared. B) radio. C) visible. D) ultraviolet. E) none of the above - ANSWER -A) infrared. What kind of thermal radiation does Earth emit? a) visible and ultraviolet light b) infrared and visible light c) infrared, visible, and ultraviolet light d) visible light e) infrared light - ANSWER -e) infrared light Earth's stratosphere is heated primarily by which process? A) Convection from the Earth's surface. B) Absorption of infrared radiation by greenhouse gases. C) Absorption of visible light by ozone. D) Absorption of ultraviolet radiation by ozone. E) Atoms and molecules absorb infrared sunlight. - ANSWER -D) Absorption of ultraviolet radiation by ozone. Convection occurs in the troposphere but not in the stratosphere because A) the troposphere is warmer than the stratosphere. B) the troposphere is cooler than the stratosphere.