Quiz 9.  NAME___________________________

1. The last impact on Earth that may have caused a major life extinction event
   a. occurred about 65 million years ago on the Yucatan peninsula
   b. caused world-wide forest fires that filled the atmosphere with smoky/dust particles
   c. deposited the rare element iridium around the entire Earth
   d. all the above
   e. Nonsense - Earth has never experienced a major life extinction other than the present one initiated by human actions.
   

2. The southern hemisphere of Mars has numerous impact craters, while the northern hemisphere does not.  The implication is that
   a. the southern hemisphere surface is much older than the northern hemisphere surface.
   b. impactors coming in from the south greatly outnumbered impactors coming in from the north.
   c. the thicker atmosphere in the northern hemisphere caused erosion of those craters.
   d. dust clouds in the northern hemisphere greatly restrict our view, and there are actually many craters in the north as well.
   

3. How do scientists explain the fact that Earth's atmosphere contains predominantly oxygen and nitrogen, with only a tiny bit of carbon dioxide?
   a. Molecular nitrogen results from volcanic venting and has been present since Earth's formation; oxygen results from ultraviolet radiation breaking up carbon dioxide molecules; the carbon dioxide is primarily from production in decaying organic material.
   b. The nitrogen results from ultraviolet breakup of ammonia in early Earth's atmosphere; the oxygen results from living organisms that excrete oxygen as a waste product; the carbon dioxide results from volcanic venting combined with removal from the atmosphere by liquid water.
   c. Outgassing of the early molten planet Earth directly produced the all the molecular nitrogen and carbon dioxide; chemical reactions between sulfuric acid (produced by volcanic activity) and rocks produced molecular oxygen and surface sulfur compounds.
   d. The only gas scientists can explain is carbon dioxide; most of it comes from decay of organic material, combined with removal from the atmosphere by liquid water. No other planets have molecular oxygen or molecular nitrogen in their atmosphere, and we don't know why Earth is unique in this respect.
   

4. How does the amount of total carbon compare for Venus and Earth, which are in many respects twin planets that formed near one another in the inner solar system?
   a. Venus' total carbon amount is much greater than that of Earth's total carbon because the carbon in Venus' atmosphere greatly exceeds that in Earth's atmosphere.
   b. Earth has far more carbon in it's fossil fuel (oil & coal) than Venus has in its atmosphere.
   c. The amount of carbon in Earth's rocks alone greatly exceeds that of Venus, which stores almost all its carbon in the atmosphere.
   d. Most of Venus' carbon is in its atmosphere, while most of Earth's carbon is in rocks; the total amounts are almost the same for the two planets.
   

5. NASA hires you to perform seismic testing on another planet by shocking the surface at one point and trying to detect seismic waves around the planet.  Suppose you detect both P and S waves around about half of the planet on your side, a shadow zone beyond that where no waves at all show up, and a patch of surface on the opposite side of the planet where you detect both P and S waves.  Describe the interior model of the mystery planet.
   a. The planet is undifferentiated and contains no liquid interior at all, so it has no identifiable high-density core.
   b. The outer part of the planet is low-density, solid mantle material; the core is solid, higher density material and extends about half-way to the surface.
   c. The planet contains an entirely liquid, high-density core that extends about half-way to the surface; a low-density, solid mantle overlies the core.
   d. The description would closely resemble the model for Earth, with a solid inner core, a liquid outer core extending about half-way to the surface, and a lower-density mantle.
   

6. Which of the following is/are properties of Earth's magnetic field?
   a. Earth's field forms natural traps for electrons and protons coming from space, thereby preventing them from ionizing our atmosphere.
   b. Earth's magnetic south pole is currently located near the north geographic pole.
   c. Earth's magnetic poles migrate significantly over long times as well as on a daily basis.
   d. In recent geologic times, Earth's magnetic field has experienced pole reversals every several hundred thousand years.
   e. All of the above.
   

7. Name two places on Earth where convection is operating on a large scale, creating natural phenomena that are important features for life on Earth.
   a. in the mantle and the core
   b. in the two van Allen belts.
   c. in the crust and the exosphere.
   d. all of the above
   e. none of the above
   

8. When an Earth scientist says that the Earth is "differentiated," she means that
   a. Earth’s magnetic field undergoes reversals.
   b. the radioactive heating of the Earth takes place at a slower rate today than it did billions of years ago.
   c. the ground beneath our feet gets hotter and more dense as you go toward the center of Earth.
   d. Earth's interior is partly molten.
   

9. The subduction of the Juan de Fuca plate (off our coast) under the North American plate results in
   a. the potential for great earthquakes where we live.
   b. formation of volcanoes such as Mt. Baker.
   c. recycling of crust material under the ocean into the mantle, and uplift of the North American plate edge.
   d. all of the above
   e. Only a and c above.
   

10. Ozone depletion in the upper atmosphere is likely to cause
    a. heating of the lower atmosphere.
    b. skin cancer.
    c. melting of the polar ice caps.
    d. all of the above.
    e. acid rain.
    

11. The observed rate of cratering on the lunar highlands helps to show that the highlands
    a. are about 1 billion years old.
    b. are about 2 billion years old.
    c. are younger than the maria.
    d. are older than the maria.
    e. the cratering rate on the moon is the same now as it has always been.
    

12. What theory of the Moon’s origin do most astronomers favor today?
    a. The Moon formed as a separate object near Earth and at about the same time.
    b. The Moon formed far from Earth and was captured by its gravity.
    c. The Moon originated as material torn from the young, molten Earth by tidal forces.
    d. The Moon originated as material torn from Earth by the collision with a Mars-sized object.
    

13. Which of the following is NOT true about Mercury?
    a. Mercury has a very weak magnetic field.
    b. Mercury's volcanic activity must have produced an early atmosphere similar to Earth's early atmosphere.
    c. Mercury has about 2 dozen active surface plates, similar to Earth's plates.
    d. Mercury lost most of its internal thermal energy due to its small size, and its internal temperatures are not high enough to support plate tectonics.
    e. Mercury does not have an active greenhouse effect because of its lack of atmosphere.
    

14. If Venus once had an ocean, where did it go?
    a. It still exists as abundant water vapor in the planet’s atmosphere.
    b. The water molecules escaped intact to space.
    c. The water broke into hydrogen and oxygen, the hydrogen escaped to space, and the oxygen became trapped in the planet’s surface rocks.
    d. It is all frozen, in the form of large polar ice caps.
    

15. Which of the following contributes to Venus’ being so much hotter than Earth?
    a. It is closer than Earth to the Sun.
    b. Its atmosphere is dense.
    c. Its atmosphere is made almost entirely of carbon dioxide.
    d. All of the above.
    

16. Venus is known to be an unusually hot planet. What part(s) of Venus is so hot?
    a. Venus has a molten core with temperatures much higher than those of Earth's core.
    b. Venus has an unusually hot molten mantle that gives rise to vast numbers of volcanoes.
    c. The atmosphere and surface are unusually hot.
    d. The crust of Venus is mostly molten and has not cooled and solidified.
    

17. When Earth had a carbon dioxide level of 280 ppm, the lower atmospheric temperature was about 35 Kelvin (63 deg F) warmer than if Earth had no greenhouse effect at all.   When human activity increases the carbon dioxide level to 560 ppm, will the temperature likely increase by another 35 Kelvin?
    a. No, because some of the present greenhouse effect is due to other gases and we cannot accurately predict the response of those gases to higher carbon dioxide levels.
    b. No, because the uncertainty in modeling many other feedback mechanisms prevents us from predicting the future temperature response accurately.
    c. No, because the past climate record includes no data for carbon dioxide levels higher than 300 ppm, so the actual correlation between carbon dioxide and temperature is unknown for carbon dioxide levels higher than 300 ppm.
    d. No, because all of items "a" through "c" are true, and we humans are doing an experiment with our planet's atmosphere whose outcome is highly uncertain.
    e. Yes, because the temperature increase (above the value corresponding to zero carbon dioxide) is proportional to the carbon dioxide level (i.e., if you double the carbon dioxide level, you double the greenhouse-induced temperature increase).
    

18. What property of Mars is responsible for producing the great heights of its volcanoes relative to Earth?
    a. Plate tectonics did not operate on Mars when its volcanoes grew.
    b. Mars has a lower surface gravity than Earth.
    c. Mars may have a thicker, more rigid crust than Earth.
    d. Each of the above probably plays a role.
    

19. Thousands of impact craters cover our Moon and Mercury, but we find only several dozen impact craters on our much larger Earth because:
    a. the surfaces of Moon and Mercury subsided as they cooled and formed craters, while Earth did not shrink as much during cooling and formed few craters.
    b. numerous planetesimals collided with Moon and Mercury, but Earth was in a region of the solar system where relatively few planetesimals existed.
    c. the surfaces of Moon and Mercury are old and retain the scars from planetesimal collisions, while Earth's surface continually obliterates its impact scars.
    d. all of the above.
    

20. Evidence of liquid water in Mars’ distant past suggests that it had a substantial atmosphere compared with what it has presently. What happened to its atmosphere?
    a. The atmospheric carbon dioxide dissolved in water and combined with surface rocks.
    b. Mars’ gravity is too weak to hold the original atmosphere of hydrogen and helium.
    c. Some of the atmosphere’s water vapor has frozen out into the polar ice caps as Mars has cooled.
    d. All of the above may have occurred.