Astronomy midterm question: Martian volcanoes reactivating?

Astronomy 210 Midterm 2, spring semester 2014
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board[*] was asked and answered:

py: What would happen if Mars' volcanoes became active again? Like if all of the sudden Olympus Mons just exploded and melted the ice caps? Would Mars' climate become more like Earth's?
Al: (a) It would be impossible for Mars' volcanoes to become active again, but (b) if they could become active, Mars' climate would then become more Earth-like.

Discuss why both these answers (a)-(b) are correct, and how you know this. Explain using the properties of greenhouse gases and geological activity.

[*] Adapted from https://answers.yahoo.com/question/index?qid=20110615233622AAjIa8s.

Solution and grading rubric:

• p = 20/20:
  Discusses why both statements are correct: (a) Mars' volcanic activity has ceased because there is no heat left in its small core, which caused it to cool off rapidly; and (b) if there was an increase in volcanic activity, outgassing and melting of polar ice caps would introduce more carbon dioxide and water vapor greenhouse gases, allowing Mars to retain more heat from the sun and increase its atmospheric temperatures.
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. One of two points (a)-(b) correct, other is problematic/incomplete.
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Both points (a)-(b) problematic/incomplete, or one point correct while other is missing.
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least understands factors that contribute to (lack of) volcanic activity and greenhouse effect.
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Discusses factors other than relevant to geological activity and greenhouse effect.
• y = 2/20:
  Irrelevant discussion/effectively blank.
• z = 0/20:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm02n4iL
p: 10 students
r: 6 students
t: 8 students
v: 2 students
x: 2 students
y: 0 students
z: 0 students

Section 30676
Exam code: midterm02sh7F
p: 18 students
r: 5 students
t: 12 students
v: 7 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 0123):
Another sample "p" response (from student 7342):
A sample "t" response (from student 1378), only discussing why Mars' volcanoes cannot erupt again:
Another sample "t" response (from student 6620), only discussing the effect of volcanic eruptions on Mars' climate:

Astronomy in-class activity: geo-atmospheric cycles and histories

Astronomy 210 In-class activity 23 v.13.06.10, fall semester 2013
Cuesta College, San Luis Obispo, CA

Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet comparing the geological and atmospheric cycle histories of Earth, Venus, and Mars. Students are already familiar with the Earth's cycles from a previous learning cycle and quiz, such that if an entry is to be used more than once, then it should appear in the same box on other planets as it does on the Earth (e.g. "CO₂").

Students apply the individual effects of distance from sun and presence of greenhouse gases, but may result in more than one plausible result for the questions on the third page, as comparing the relative amounts of competing effects is not covered in the scope of this course.

Astronomy final exam question: Mars' past history

Astronomy 210 Final Exam, fall semester 2012
Cuesta College, San Luis Obispo, CA

An article on an online science and science fiction discussion blog(*) discusses the past history and possibility of future colonization of Mars:

So, what happened on Mars? When volcanic activity halted on Mars...this once warm and inviting place, with enough atmospheric pressure and a high enough temperature to support liquid water, become a frozen rock with [a thin] atmosphere...

Discuss how the end of volcanic activity on Mars caused temperatures to drop and its atmosphere to become thinner. Explain using the properties of greenhouse gases and geological activity.

(*)Jason Shankel, "How We Will Terraform Mars," December 19, 2011, io9.com/5868115/how-we-will-terraform-mars.

Solution and grading rubric:

• p:
  Correct. Discusses features of the "runaway refrigerator" model of Mars' past: (a) Mars' small mass would make it unable to retain its atmosphere due to its slower escape velocity, (such that its atmosphere thins), and thus (b) unable to retain enough heat (such that its temperatures will drop). May also have discussed how Mars' oceans removed greenhouse gases from the atmosphere.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. One of two points (a)-(b) correct, other is problematic/incomplete.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Both points (a)-(b) problematic/incomplete, or one point correct while other is missing.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least understands factors that contribute to atmosphere retention and greenhouse effect.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discusses factors other than relevant to atmosphere retention and greenhouse effect.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 70158
Exam code: finalSor3
p: 7 students
r: 9 students
t: 9 students
v: 3 students
x: 1 student
y: 0 students
z: 0 students

Section 70160
Exam code: finalNon0
p: 6 students
r: 9 students
t: 8 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 2192):

Astronomy final exam question: Earth avoiding Venus' runaway greenhouse?

Astronomy 210 Final Exam, spring semester 2011
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board (http://answers.yahoo.com/question/index?qid=20101122180043AAVRumU) was asked and answered:

Samantha: How did Earth avoid the runaway greenhouse effect that made Venus so hot?
Paul: The reason that Earth managed to avoid a catastrophic runaway greenhouse effect was its level of geologic activity... Venus, on the other hand, is a geologically inactive planet, with no way of recycling [carbon dioxide].

Discuss whether or not if this answer is correct, and how you know this. Explain using the properties of greenhouse gases and geological activity.

Solution and grading rubric:

• p = 20/20:
  Correct. Understands how oceans absorb carbon dioxide (which eventually gets subducted into the mantle), and specifically discusses how Earth avoided runaway greenhouse effect by being farther away from the sun than Venus.
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. As (p), but does not discuss how location was key for Earth to avoid runaway greenhouse effect as on Venus.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least recognizes factors that contribute to and/or control greenhouse effect.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discusses factors that do not contribute to and/or control greenhouse effect.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
Exam code: finaln4St
p: 12 students
r: 7 students
t: 8 students
v: 2 students
x: 0 students
y: 0 students
z: 1 student

Section 30676
Exam code: finalS45s
p: 10 students
r: 12 students
t: 8 students
v: 12 students
x: 0 students
y: 0 students
z: 1 student

A sample "p" response (from student 1440):

A sample "r" response (from student 0701):

Astronomy quiz question: carbon dioxide sink

Astronomy 210 Quiz 7, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

Where does the carbon dioxide in Earth's atmosphere go before it is recycled back down into the mantle?
(A) Volcanoes.
(B) Plants.
(C) Oceans.
(D) Polar ice caps.

Correct answer: (C)

Oceans absorb vast amounts of carbon dioxide, which settle into sedimentary rocks on ocean floors, which are then subsequently subducted back into the mantle.

Section 30674
Exam code: quiz07N3mi
(A) : 4 students
(B) : 6 students
(C) : 26 students
(D) : 0 students

"Success level": 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

Section 30676
Exam code: quiz07Sq5h
(A) : 3 students
(B) : 12 students
(C) : 22 students
(D) : 3 students

"Success level": 59% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82

Compare to a similar version of this question from Fall 2009.

Astronomy final exam question: runaway greenhouse or runaway refrigerator

Astronomy 210 Final Exam, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

[Version 1]

[20 points.] If tectonic plate motion continued on Earth (but volcanic activity stopped), discuss how it would either become a runaway refrigerator (like Mars), or a runaway greenhouse (like Venus). Explain using properties of the geological/atmospheric cycles of planets.

Solution and grading rubric:

• p = 20/20:
  Correct. Ceasing volcanic activity means no carbon dioxide released back from the mantle into the atmosphere, while tectonic plate motion continues to subduct carbon dioxide in ocean sediments back into the mantle, decreasing the greenhouse effect and causing cooler temperatures. (The runaway refrigerator effect is when it is cold enough for the oceans to freeze, such that water vapor (also a greenhouse gas) is no longer present in the atmosphere, and thus even colder temperatures will take place; this much detail is not required as long as the lack of source, and continued sink in the carbon cycle are both mentioned.)
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses lack of source and continued sink, but one of these is slightly problematic.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Typically discusses lack of source, but not continued sink.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Lack of heat from volcanoes that would otherwise maintain warm atmospheric temperatures, or other factors.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
p: 8 students
r: 9 students
t: 6 students
v: 14 students
x: 1 student
y: 2 students
z: 0 students

A sample "p" response (from student 8479):


A sample "r" response (from student 2569), with no discussion on carbon dioxide intake by oceans (and subsequent subduction of carbon-bearing sediments down into the mantle):


A sample "v" response (from student 7109), touching upon end of plant life and nuclear winter scenarios:


A sample "y" response (from student 0000), with a fanciful illustration:


[Version 2]

[20 points.] If tectonic plate motion stopped on Earth (but volcanic activity continued), discuss how it would either become a runaway refrigerator (like Mars), or a runaway greenhouse (like Venus). Explain using properties of the geological/atmospheric cycles of planets.

Solution and grading rubric:

• p = 20/20:
  Correct. Tectonic plate motion ceasing to subduct carbon dioxide in ocean sediments back into the mantle, and continuing volcanic activity releasing carbon dioxide from the mantle into the atmosphere would increase the greenhouse
  effect and causing warmer temperatures. (The _runaway_ greenhouse effect is when it becomes warm enough for the oceans to evaporate, such that water vapor (also a greenhouse gas) is now prevalent in the atmosphere, and thus even hotter temperatures will take place; this much detail is not required as long as the lack of sink, and continued source in the carbon cycle are both mentioned.)
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses lack of sink and continued source, but one of these is slightly problematic.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Typically discusses continued source, but not lack of sink.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Heat from volcanoes would directly cause warm atmospheric temperatures, or other factors.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
p: 6 students
r: 6 students
t: 13 students
v: 26 students
x: 12 students
y: 4 students
z: 1 student

A sample "p" response (from student 9998):


A sample "v" response (from student 3455), taking into consideration the heat produced by friction between moving tectonic plates:


A sample "x" response (from student 5611), using uppercase to underscore the importance of convection:


A sample "y" response (from student 4000):

Astronomy quiz question: carbon dioxide sink

Astronomy 210 Quiz 7, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

What prevents Earth's atmosphere from building up too much carbon dioxide?
(A) Volcanoes.
(B) Oceans.
(C) Plants.
(D) The greenhouse effect.

Correct answer: (B)

Oceans absorb vast amounts of carbon dioxide, which settle into sedimentary rocks on ocean floors, which are then subsequently subducted back into the mantle.

Section 70158
(A) : 0 students
(B) : 26 students
(C) : 15 students
(D) : 2 students

Success level: 65% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

Astronomy final exam question: Mars as runaway refrigerator

Astronomy 210 Final Exam, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] If all volcanic activity ceased on Earth, discuss how it would eventually either become a runaway refrigerator (like Mars), or a runaway greenhouse (like Venus). Explain using properties of the geological/atmospheric cycles of planets.

Solution and grading rubric:

• p = 20/20:
  Correct. Decreasing volcanic activity means less carbon dioxide released from the mantle into the atmosphere, decreasing the greenhouse effect and causing cooler temperatures. The runaway refrigerator effect is when it is cold enough for the oceans to freeze, such that water vapor (also a greenhouse gas) is now missing in the atmosphere, and thus even colder temperatures will take place.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Explains how Earth's greenhouse effect will get weaker and colder temperatures would result, but not how the freezing of oceans and lack of water vapor would accelerate this effect.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Understands how lack of carbon dioxide would decrease the greenhouse effect.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
p: 0 students
r: 8 students
t: 8 students
v: 10 students
x: 1 student
y: 3 students
z: 1 student

A sample "r" response (from student 5398), not quite explaining how lowering temperatures would accelerate ("runaway") once water vapor freezes out of a cooling atmosphere:

A sample "v" response (from student 5238), where the apparently the heat supplied by volcanoes that is now missing would cause temperatures to lower:

Another sample "v" response (from student 9898), where the lack of fertile volcanic soil for plant growth will eventually cause the atmosphere to heat up, much like Venus'(!) atmosphere:

A sample "y" response (from student 1228), going for the cheap joke:

Another sample "y" response (from student 1959), with a visual pun:

Astronomy final exam question: closer Mars?

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] If Mars had originally formed closer to the Sun, discuss whether its atmosphere would now be thinner than, thicker than, or the same as it is today. Explain your reasoning.

Solution and grading rubric:

• p = 20/20:
  Correct. Mars lost its atmosphere due to two effects--its weak gravity (due to its small mass) is unable to hold on to molecules in its atmosphere, and lack of an ozone layer allowed ultraviolet light to break down molecules into constituent atoms, allowing them to more easily escape. Having Mars form closer to the Sun would exacerbate both effects, as a higher temperature would cause molecules/atoms in the atmosphere to move faster. (May refer to escaping molecules as due to the Sun "burning off" the atmosphere, or calls this process "outgassing").
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses how Mars would then be warm enough to have oceans and water vapor would contribute to a temporarily more thicker atmosphere.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Some discussion of difference in lifetimes, but compounded/confounded with other factors. Garbled discussion, but recognition of related factors such as mass, ozone layer, distance from Sun, temperature, and greenhouse effect.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Involving unrelated factors, such as an inverse correlation between distance from Sun and thickness of atmosphere, Mars now being in the habitable zone and thus sustaining life, or heat causing Mars' surface to begin outgassing.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70158
p: 18 students
r: 11 students
t: 15 students
v: 24 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response for Mars having a thinner atmosphere (from student 3259):

A sample "p" response for Mars having a thicker (albeit, temporarily so) atmosphere (from student 7070):

A sample "r" response (from student 0013):

Examples of sample "t" responses, discussing how the position would determine the thinness/thickness of an atmosphere, but with no discussion as to why this would be so (here, from student 0725):

(...and from student 1616):

(...and from student 9933):

Astronomy final exam question: Venus vs. Earth carbon dioxide

Astronomy 210 Final Exam, fall semester 2008
Cuesta College, San Luis Obispo, CA

Discuss why Venus' atmosphere currently has more carbon dioxide than Earth's atmosphere, even though volcanic activity on both planets outgassed the same amount of carbon dioxide. Explain using the properties of greenhouse gases and geological activity.

Solution and grading rubric:

• p:
  Correct. Due to Venus being closer to the sun than Earth, Venus' oceans evaporated and this water vapor contributed to its "runaway greenhouse effect," as there is no way to reduce the carbon dioxide in its atmosphere, compared to Earth's oceans, which do manage to provide a sink for its carbon dioxide.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May involve plants in addition to oceans.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Garbled discussion, but recognition of related factors such as distance from Sun, mass, temperature, and the greenhouse effect.
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss how certain stars are fainter, or blocked by intervening matter, etc.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Involving unrelated factors.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 70160
p: 16 students
r: 3 students
t: 9 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, illustrated (from student 1225):
Another sample illustrated "p" response (from student 0911):
A somewhat macabre illustrated "r" response (from student 1083):

Astronomy midterm question: comparing atmospheric CO_2 abundances

Astronomy 10 Midterm 2, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q5.5

[15 points.] Currently, carbon dioxide (CO_2) makes up about 95% of Venus' atmosphere, and also makes up about 95% of Mars' atmosphere. Explain why carbon dioxide makes up a much smaller percentage of the Earth's atmosphere

Solution and grading rubric:

• p = 15/15:
  Correct. Earth has oceans and tectonic plate motion, while Venus and Mars do not. CO_2 in the Earth's atmosphere is absorbed by the oceans, then is incorporated into sedimentary rock on the ocean floor, which is then subducted back into the mantle.
  
• r = 12/15:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Recognizes importance of oceans or tectonic plate motion, but does not explicitly describe both. Or as (p), but also cites less CO_2 released by volcanos relative to Venus and/or Mars as contributing factor.
  
• t = 9/15:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least recognizes that CO_2 is somehow being cycled out of the atmosphere back into the mantle.
  
• v = 6/15:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Appeals to plant life, greenhouse effect, or attaining escape velocity as the primary removers of CO_2 from the atmosphere.
  
• x = 3/15:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 1.5/15:
  Irrelevant discussion/effectively blank.
  
• z = 0/15:
  Blank.
  

Grading distributions:
Section 4160
p: 13 students
r: 15 students
t: 0 students
v: 12 students
x: 0 students
y: 0 students
z: 0 students

Section 5166
p: 15 students
r: 20 students
t: 5 students
v: 22 students
x: 1 student
y: 0 students
z: 1 student

A sample "p" response (from student 1223, who memorized the Earth carbon cycle chart from In-class activity 12):

Another "p" response (from student 6221):

And one more "p" response (from student 8994), who, despite discussing plants as an important factor in cycling excess carbon dioxide out of the Earth's atmosphere, emphasizes the contribution of oceans, sedimentary rocks, and tectonic plate motion with an illustration:

Previous posts:
Astronomy in-class activity: geo-atmospheric cycles and histories
Astronomy quiz question: carbon dioxide source
Astronomy quiz question: carbon dioxide sink
Astronomy quiz question: Venus' atmosphere
Astronomy quiz question: Mars' atmosphere

Astronomy quiz question: Mars' atmosphere

Astronomy 10 Quiz 5, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q5.5

[3.0 points.] Which one of the following choices best explains how carbon dioxide (CO_2) molecules caused the recent evolution of Mars to diverge from that of the Earth?
(A) CO_2 from the atmosphere was removed without being replaced, causing Mars' atmosphere to become thinner and colder.
(B) More CO_2 was released into the atmosphere than could be recycled, causing Mars' atmosphere to become thinner and colder.
(C) CO_2 was removed from the atmosphere without being replaced, causing Mars' atmosphere to become thicker and hotter.
(D) Too much CO_2 was released into the atmosphere, causing Mars' atmosphere to become thicker and hotter.
(E) More CO_2 was released into the atmosphere than could be recycled, causing Mars' atmosphere to become thicker and hotter.

Correct answer: (A).

Student responses
Section 5166
(A) : 30 students
(B) : 19 students
(C) : 2 students
(D) : 4 students
(E) : 5 students

Previous post: Astronomy in-class activity: geo-atmospheric cycles and histories

Astronomy quiz question: Venus' atmosphere

Astronomy 10 Quiz 5, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q5.5

[3.0 points.] Which one of the following choices best explains how carbon dioxide (CO_2) molecules caused the recent evolution of Venus atmosphere to diverge from that of the Earth?
(A) CO_2 from the atmosphere was removed without being replaced, causing Venus' atmosphere to become thinner and colder.
(B) More CO_2 was released into the atmosphere than could be recycled, causing Venus' atmosphere to become thinner and colder.
(C) CO_2 was removed from the atmosphere without being replaced, causing Venus' atmosphere to become thicker and hotter.
(D) Too much CO_2 was released into the atmosphere, causing Venus' atmosphere to become thicker and hotter.
(E) More CO_2 was released into the atmosphere than could be recycled, causing Venus' atmosphere to become thicker and hotter.

Correct answer: (E).

Student responses
Section 4160
(A) : 1 student
(B) : 3 students
(C) : 2 students
(D) : 11 students
(E) : 21 students

Previous post: Astronomy in-class activity: geo-atmospheric cycles and histories

Astronomy quiz question: carbon dioxide source

Astronomy 10 Quiz 4, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q4.4

[3.0 points.] Which one of the following choices best describes the main source of carbon dioxide (CO_2) molecules in the Earth's atmosphere?
(A) Plant growth.
(B) Comets.
(C) Global warming produced by modern industry.
(D) Volcanos.
(E) Tectonic plate motion.

Correct answer: (D).

Volcanos are the main source of carbon dioxide in the atmosphere. Modern industry manages to take the carbon dioxide that was sequestered from the atmosphere by plants, and recycle it back into the atmosphere. Ultimately, oceans absorb and convert atmosphere carbon dioxide into sedimentary rock, which is then subducted into the mantle by tectonic plate motion.

Student responses
Section 5166
(A) : 9 students
(B) : 0 students
(C) : 11 students
(D) : 29 students
(E) : 7 students

Related post: Astronomy quiz question: carbon dioxide sink

Astronomy quiz question: carbon dioxide sink

Astronomy 10 Quiz 4, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q4.4

[3.0 points.] Which one of the following choices best describes what prevents too much carbon dioxide (CO_2) molecules from building up in the Earth's atmosphere?
(A) Large amounts of dry ice produced for modern industry.
(B) Global warming produced by modern industry.
(C) Tectonic plate motion.
(D) Plant growth.
(E) Volcanos.

Correct answer: (C).

Oceans absorb carbon dioxide from the atmosphere, which then settles down and is incorporated into carbonaceous sedimentary rock. This sequestered carbon then is ultimately taken back down into the mantle at subduction trenches.

Student responses
Section 4160
(A) : 0 students
(B) : 0 students
(C) : 26 students
(D) : 6 students
(E) : 9 students

Related post: Astronomy quiz question: carbon dioxide source

Astronomy midterm question: runaway greenhouse or refrigerator

Astronomy 10 Midterm 2, Fall Semester 2007
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q5.5

[Version 1]
[15 points.] If volcanic activity drastically increased on the Earth, discuss how it would either become a runaway refrigerator (like Mars), or a runaway greenhouse (like Venus). Explain using properties of the geological/atmospheric cycles of planets.

Solution and grading rubric:

• p = 15/15: Correct. Increasing volcanic activity means more carbon dioxide released back from the mantle into the atmosphere, increasing the greenhouse effect and causing cooler temperatures. The runaway greenhouse effect is when it is hot enough for the oceans to evaporate, such that water vapor (also a greenhouse gas) is now prevalent in the atmosphere, and thus even hotter temperatures will take place.
  
• r = 12/15:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Explains how Earth's greenhouse effect will get stronger and hotter temperatures would result, but not how the evaporation of oceans and prevalence of water vapor will accelerate this effect.
  
• t = 9/15:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Understands how carbon dioxide produces a greenhouse effect, and how an increase in volcanic activity would generate higher temperatures.
  
• v = 6/15:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 3/15:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 1.5/15:
  Irrelevant discussion/effectively blank.
  
• z = 0/15:
  Blank.
  

Grading distribution:
Section 0135
p: 7 students
r: 8 students
t: 3 students
v: 13 students
x: 6 students
y: 1 student
z: 0 students

A sample of a "p" response (from student 2001) is shown below:

[Version 2]
[15 points.] If volcanic activity drastically increased on the Earth, discuss how it would either become a runaway refrigerator (like Mars), or a runaway greenhouse (like Venus). Explain using properties of the geological/atmospheric cycles of planets.

Solution and grading rubric:

• p = 15/15: Correct. Tectonic plate motion recycles sedimentary rock of ocean floors (which contains carbon dioxide from the atmosphere) down into the mantle. Decreasing volcanic activity means less carbon dioxide released back from the mantle into the atmosphere, decreasing the greenhouse effect and causing cooler temperatures. The runaway refrigerator effect is when it is cold enough for the oceans to freeze, such that water vapor (also a greenhouse gas) is no longer present in the atmosphere, and thus even colder temperatures will take place.
  
• r = 12/15:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Explains how Earth's greenhouse effect will get weaker and cooler temperatures would result, but not how the freezing oceans and lack of water vapor will accelerate this effect.
  
• t = 9/15:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Discusses how no new carbon dioxide put into the atmosphere by volcanos would result in lower temperatures, without mentioning that the process that removes carbon dioxide from the atmosphere is still continuing.
  
• v = 6/15:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss how lack of volcanos and continuing tectonic plate motion will result in a runaway greenhouse effect.
  
• x = 3/15:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 1.5/15:
  Irrelevant discussion/effectively blank.
  
• z = 0/15:
  Blank.
  

Grading distribution:
Section 1073
p: 1 student
r: 13 students
t: 13 students
v: 15 students
x: 5 students
y: 0 students
z: 0 students

A sample of a "p" response (from student 7823) is shown below: