Assignment 3 - 2023
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School
McGill University *
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Course
200
Subject
Geology
Date
Dec 6, 2023
Type
docx
Pages
3
Uploaded by ConstableRiverPheasant27
Assignment #3
1.
[2 pts] Which of the following processes act as SOURCES for atmospheric CO2? [Choose ALL
answers that apply]
a)
The formation of new crust at mid-oceanic ridges.
b)
Chemical weathering of carbonate rocks
c)
Sedimentation of carbon in the ocean
d)
Volcanic activity
e)
All of the above
2.
[1 pt] The Earth steadily cooled from about 65 million years ago to about 1 million years ago. The
PRIMARY reason for this cooling was
a)
A reduction in the intensity of the Sun
b)
A change in the albedo of the Earth
c)
The Milankovich cycle
d)
The scouring of CO2 from the atmosphere from the chemical weathering of rock
e)
The evolution of terrestrial plants
3.
[1 pt] In a warmer climate, we should expect the rate of chemical weathering of rocks to
a)
Increase
b)
Decrease slowly
c)
Decrease rapidly
d)
Initially decrease then become constant
e)
Remain unchanged
4.
[2 pts] While the Milankovich cycle is thought to trigger/end glaciations, the changes in Solar
radiation are not sufficient to explain changes in planetary temperature. Which of the following
feedbacks act to amplify changes in temperature triggered by the Milankovich cycle? [Choose
ALL that apply]
a)
Ice-albedo feedback
b)
Chemical solubility of CO2 in the ocean
c)
Change in terrestrial biomass
d)
Change in tectonic activity
e)
Change in geothermal activity
5.
[1pt] What is the average length of time water remains in the atmosphere?
a)
11 years
b)
11 months
c)
11 weeks
d)
11 days
e)
11 hours
6.
[2 pts] Consider the following diagram of the carbon cycle.
The amount of CO2 in the atmosphere prior to the industrial revolution remained at ~590 Gt
for thousands of years. Since that time, 240 Gt has been added to the atmosphere.
Assuming that the
net flux
of CO2 out of the atmosphere remains unchanged, if fossil fuel
and land use emissions were to cease, how many years would it take for anthropogenic CO2
to be removed by the short-term carbon cycle (i.e. land & ocean fluxes)? Show your
calculations [use mean values only, ignoring the (±) error bars]. Hint: Think in terms of
residence time.
7.
[1 pt] What form(s) of carbon is(are) typically released by volcanic activity? Select all that apply:
a)
Calcium carbonate
b)
Carbon dioxide
c)
Methane
d)
Hydrocarbons
e)
Calcium silicate
8.
[1 pt] Which of the following statements is incorrect?
a)
The current atmospheric CO2 concentration the highest it has been in over 420,000 years.
b)
During glacial periods, the oceans tend to become more enriched in the
18
O
2
isotope.
c)
The largest organic carbon reservoir is the fossil fuel reservoir.
d)
Carbonate rock weathering releases calcium and bicarbonate ions.
e)
Terrestrial plants in northern hemisphere in winter respire more CO
2
than they absorb
9.
[4 pts] Imagine you have a food chain containing 5 trophic levels: grass (primary producer),
grasshoppers (herbivore), frogs (insectivore) and owls (top predator). Assume that no organisms
die due to reasons other than consumption, and there is a 10% energy transfer efficiency
between all trophic levels, and that the entire standing plant biomass has the energetic
equivalence of 750,000 Joules.
a) How much energy is available to the top predator? Show your work.
b)
Assuming the lower levels of the food web were subjected to top-down control, if all the owls
disappeared then what would likely happen to plant biomass?
c)
Suppose the gross primary production is 1000 g m
-2
yr
-1
, plant respiration is 200 g m
-2
yr
-1
, and
the net ecosystem production is 100 g m
-2
yr
-1
. What is the combined respiration of the
grasshoppers, frogs and owls? Show your work.
d)
Given the information in part c above, is carbon storage in the system positive, negative, or
zero?
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