Earth Science Quiz: Earth System Diagrams

What this quiz covers

This quiz focuses on Earth System Diagrams, giving you a quick way to practice the rules, question types, and explanations that matter most for Earth Science.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. The imbalance is negligible and will be corrected by natural negative feedbacks within a few decades, having no long-term effect.
2. It will lead to a massive transfer of carbon, potentially altering the chemistry of the entire ocean reservoir and significantly lowering atmospheric carbon levels. (correct answer)
3. The deep ocean reservoir will become saturated with carbon, reversing the flux and releasing a large amount of carbon back to the atmosphere.
4. It will primarily affect the terrestrial biosphere reservoir as plants adapt to lower atmospheric carbon concentrations.

Explanation: This question requires scaling a small annual flux over a long timescale. A flux of +0.5 GtC/year, when integrated over one million years, results in a total transfer of 0.5 * 1,000,000 = 500,000 GtC. This is a colossal amount of carbon—larger than the current atmospheric, terrestrial, and surface ocean reservoirs combined. Such a transfer would dramatically alter the size and chemistry of the ocean carbon reservoir and would represent a major drawdown of carbon from the atmosphere-land-surface ocean system. The other options underestimate the power of accumulating small changes over vast timescales.

Question 2

1. 50 years
2. 0.05 years
3. 10 years
4. 20 years (correct answer)

Explanation: When you encounter box model problems in earth science, you're dealing with reservoirs and fluxes - fundamental concepts for understanding how substances move through Earth's systems like the carbon cycle or water cycle. To find residence time, you need to understand what it represents: the average time a substance spends in a reservoir. The formula is residence time = reservoir size ÷ outflow flux, or $τ = \frac{R}{O}$. Since the system starts in steady state, inflow equals outflow. With inflow at 50 units/year and the reservoir at 1000 units, the outflow must also be 50 units/year. You can verify this using the given rule: $O = 0.05 × R = 0.05 × 1000 = 50$ units/year. Now calculate: $τ = \frac{1000}{50} = 20$ years. The correct answer is D. Here's why the other options are wrong: A) 50 years incorrectly uses the inflow rate as the denominator instead of properly calculating residence time. B) 0.05 years confuses the proportionality constant (0.05) with residence time - a common trap when students mix up the given parameters. C) 10 years likely results from incorrectly using twice the outflow rate in the denominator, perhaps from double-counting or misunderstanding the steady-state condition. Remember this key relationship: residence time always equals reservoir size divided by the rate at which material leaves the reservoir. In steady-state problems, focus on the balance between inflows and outflows first, then apply the residence time formula.

Question 3

1. A decrease in the size of the igneous reservoir and an increase in the sedimentary reservoir due to enhanced weathering.
2. An increase in the flux of melting, leading to a larger igneous reservoir, and an increase in the flux of weathering from uplifted rock. (correct answer)
3. A shift toward steady state, where the fluxes of melting, burial, and weathering become equal in magnitude.
4. A decrease in the metamorphic reservoir as increased surface processes convert all rock types directly to sediment.

Explanation: Increased tectonic activity has two major effects relevant to the rock cycle. First, more volcanism means more magma is generated and cools, increasing the flux of melting and crystallization and thus enlarging the igneous rock reservoir. Second, mountain building (orogeny) uplifts rock, exposing it to the elements and increasing the rates of weathering and erosion, which is the flux that creates sediment. The other options are less likely. Increased tectonic activity would likely increase, not decrease, the igneous reservoir (A). It would perturb the system away from any previous steady state (C). Metamorphism is often associated with tectonic pressure and heat, so the metamorphic reservoir might also increase, not decrease (D).

Question 4

1. Denitrification, a process where soil bacteria convert nitrates back into gaseous nitrogen.
2. Assimilation, the process where plants take up nitrates and ammonia from the soil through their roots.
3. Nitrogen fixation, a process carried out by lightning and certain bacteria that converts N₂ into ammonia. (correct answer)
4. Ammonification, the decomposition of organic matter by bacteria and fungi, which releases ammonium.

Explanation: This question requires identifying the specific flux that connects the atmospheric reservoir to the biosphere. The vast majority of atmospheric nitrogen is in the form of N₂, which is unusable by most organisms. Nitrogen fixation is the crucial process that converts inert N₂ gas into biologically available forms like ammonia (NH₃). Denitrification (A) is the reverse flux. Assimilation (B) moves nitrogen within the biosphere (from soil to plants). Ammonification (D) also recycles nitrogen within the biosphere/pedosphere.

Question 5

1. Its large volume allows it to absorb vast quantities of CO₂, but the flux from the surface ocean to the deep ocean is extremely slow. (correct answer)
2. Chemical reactions in the deep ocean quickly neutralize CO₂, but these reactions are easily saturated and stop working on short timescales.
3. The deep ocean has a small volume but a very rapid exchange rate with the atmosphere, allowing it to quickly respond but not store much carbon.
4. Its buffering capacity only works in the short term, as over long periods the absorbed CO₂ is released back to the atmosphere via volcanoes.

Explanation: A reservoir's buffering capacity depends on both its size and the rate of exchange with other reservoirs. The deep ocean has an immense volume and thus a huge capacity to store carbon. This makes it an effective long-term buffer. However, the flux that moves carbon from the surface ocean to the deep ocean (the thermohaline circulation and biological pump) is very slow, with a timescale of centuries to millennia. This slow flux means the deep ocean cannot absorb the rapid, large-scale emissions of anthropogenic CO₂ on a short-term (years to decades) basis, making it an ineffective short-term buffer.

Question 6

1. A decrease in the size of the igneous reservoir and an increase in the sedimentary reservoir due to enhanced weathering.
2. An increase in the flux of melting, leading to a larger igneous reservoir, and an increase in the flux of weathering from uplifted rock. (correct answer)
3. A shift toward steady state, where the fluxes of melting, burial, and weathering become equal in magnitude.
4. A decrease in the metamorphic reservoir as increased surface processes convert all rock types directly to sediment.

Explanation: Increased tectonic activity has two major effects relevant to the rock cycle. First, more volcanism means more magma is generated and cools, increasing the flux of melting and crystallization and thus enlarging the igneous rock reservoir. Second, mountain building (orogeny) uplifts rock, exposing it to the elements and increasing the rates of weathering and erosion, which is the flux that creates sediment. The other options are less likely. Increased tectonic activity would likely increase, not decrease, the igneous reservoir (A). It would perturb the system away from any previous steady state (C). Metamorphism is often associated with tectonic pressure and heat, so the metamorphic reservoir might also increase, not decrease (D).

Question 7

1. Its large volume allows it to absorb vast quantities of CO₂, but the flux from the surface ocean to the deep ocean is extremely slow. (correct answer)
2. Chemical reactions in the deep ocean quickly neutralize CO₂, but these reactions are easily saturated and stop working on short timescales.
3. The deep ocean has a small volume but a very rapid exchange rate with the atmosphere, allowing it to quickly respond but not store much carbon.
4. Its buffering capacity only works in the short term, as over long periods the absorbed CO₂ is released back to the atmosphere via volcanoes.

Explanation: A reservoir's buffering capacity depends on both its size and the rate of exchange with other reservoirs. The deep ocean has an immense volume and thus a huge capacity to store carbon. This makes it an effective long-term buffer. However, the flux that moves carbon from the surface ocean to the deep ocean (the thermohaline circulation and biological pump) is very slow, with a timescale of centuries to millennia. This slow flux means the deep ocean cannot absorb the rapid, large-scale emissions of anthropogenic CO₂ on a short-term (years to decades) basis, making it an ineffective short-term buffer.

Question 8

1. 50 years
2. 0.05 years
3. 10 years
4. 20 years (correct answer)

Explanation: When you encounter box model problems in earth science, you're dealing with reservoirs and fluxes - fundamental concepts for understanding how substances move through Earth's systems like the carbon cycle or water cycle. To find residence time, you need to understand what it represents: the average time a substance spends in a reservoir. The formula is residence time = reservoir size ÷ outflow flux, or $τ = \frac{R}{O}$. Since the system starts in steady state, inflow equals outflow. With inflow at 50 units/year and the reservoir at 1000 units, the outflow must also be 50 units/year. You can verify this using the given rule: $O = 0.05 × R = 0.05 × 1000 = 50$ units/year. Now calculate: $τ = \frac{1000}{50} = 20$ years. The correct answer is D. Here's why the other options are wrong: A) 50 years incorrectly uses the inflow rate as the denominator instead of properly calculating residence time. B) 0.05 years confuses the proportionality constant (0.05) with residence time - a common trap when students mix up the given parameters. C) 10 years likely results from incorrectly using twice the outflow rate in the denominator, perhaps from double-counting or misunderstanding the steady-state condition. Remember this key relationship: residence time always equals reservoir size divided by the rate at which material leaves the reservoir. In steady-state problems, focus on the balance between inflows and outflows first, then apply the residence time formula.

Question 9

1. Denitrification, a process where soil bacteria convert nitrates back into gaseous nitrogen.
2. Assimilation, the process where plants take up nitrates and ammonia from the soil through their roots.
3. Nitrogen fixation, a process carried out by lightning and certain bacteria that converts N₂ into ammonia. (correct answer)
4. Ammonification, the decomposition of organic matter by bacteria and fungi, which releases ammonium.

Explanation: This question requires identifying the specific flux that connects the atmospheric reservoir to the biosphere. The vast majority of atmospheric nitrogen is in the form of N₂, which is unusable by most organisms. Nitrogen fixation is the crucial process that converts inert N₂ gas into biologically available forms like ammonia (NH₃). Denitrification (A) is the reverse flux. Assimilation (B) moves nitrogen within the biosphere (from soil to plants). Ammonification (D) also recycles nitrogen within the biosphere/pedosphere.

Question 10

1. The imbalance is negligible and will be corrected by natural negative feedbacks within a few decades, having no long-term effect.
2. It will lead to a massive transfer of carbon, potentially altering the chemistry of the entire ocean reservoir and significantly lowering atmospheric carbon levels. (correct answer)
3. The deep ocean reservoir will become saturated with carbon, reversing the flux and releasing a large amount of carbon back to the atmosphere.
4. It will primarily affect the terrestrial biosphere reservoir as plants adapt to lower atmospheric carbon concentrations.

Explanation: This question requires scaling a small annual flux over a long timescale. A flux of +0.5 GtC/year, when integrated over one million years, results in a total transfer of 0.5 * 1,000,000 = 500,000 GtC. This is a colossal amount of carbon—larger than the current atmospheric, terrestrial, and surface ocean reservoirs combined. Such a transfer would dramatically alter the size and chemistry of the ocean carbon reservoir and would represent a major drawdown of carbon from the atmosphere-land-surface ocean system. The other options underestimate the power of accumulating small changes over vast timescales.

Question 11

1. The system self-corrects by increasing snow cover, which reflects more sunlight and dampens the initial warming, representing a negative feedback loop.
2. The system amplifies the initial warming as reduced ice cover leads to more absorption of solar energy, representing a positive feedback loop. (correct answer)
3. The system enters a new stable state where decreased albedo is balanced by increased cloud formation, representing a stabilizing feedback loop.
4. The system's response is neutral because the increased absorption of energy is offset by greater heat loss from the darker ocean surface, representing no net feedback.

Explanation: The diagram shows a cyclical process where an initial warming causes ice and snow to melt. This reduces the Earth's albedo (reflectivity), causing more solar radiation to be absorbed. This absorption leads to further warming, which in turn melts more ice. This is a classic example of a positive feedback loop, where the initial perturbation is amplified by the system's response.

Question 12

1. Flux A: Incoming solar radiation absorbed by the atmosphere.
2. Flux B: Solar radiation reflected from the Earth's surface.
3. Flux C: Longwave radiation emitted from the atmosphere back to the surface. (correct answer)
4. Flux D: Longwave radiation emitted from the surface that escapes to space.

Explanation: The greenhouse effect is not the initial absorption of solar energy, but rather the trapping of outgoing longwave (infrared) radiation. The Earth's surface radiates heat (longwave radiation). Greenhouse gases absorb this radiation and re-radiate it in all directions, including back down to the surface. Flux C, 'Back Radiation', represents this downward re-radiation of longwave energy, which warms the surface beyond what it would be from solar radiation alone.

Question 13

1. The residence time in the atmosphere is significantly shorter because its reservoir size is very small compared to the large fluxes moving through it. (correct answer)
2. The residence time in the oceans is shorter because the flux rate of evaporation is larger than the flux rate of precipitation over the oceans.
3. The residence times are nearly equal because the total amount of water evaporating from the oceans and land is balanced by total precipitation.
4. The residence time in the atmosphere is longer because atmospheric water vapor can be transported long distances before precipitating.

Explanation: Residence time is conceptually calculated as Reservoir Size / Total Flux Out. For the atmosphere, the reservoir is small (13,000 km³) and the fluxes are large (total outflow is 420,000 + 110,000 = 530,000 km³/yr), resulting in a very short residence time (days). For the oceans, the reservoir is enormous (1,350,000,000 km³) and the total flux out (evaporation) is relatively small (530,000 km³/yr), resulting in a very long residence time (thousands of years). Therefore, the atmospheric residence time is significantly shorter.

Question 14

1. The atmospheric carbon reservoir is in a steady state, as the fluxes from respiration and fossil fuels are balanced by photosynthesis.
2. The net flux of carbon is from the oceans to the atmosphere, contributing to the observed increase in atmospheric CO₂.
3. The flux of carbon from fossil fuel combustion is the largest single flux shown on the diagram.
4. The atmosphere is experiencing a net accumulation of carbon each year due to an imbalance in the depicted fluxes. (correct answer)

Explanation: To determine if the atmospheric reservoir is accumulating carbon, we must sum all inflows and outflows. Inflows: Respiration (120), Ocean Release (90), Fossil Fuels (9). Total Inflow = 219 GtC/yr. Outflows: Photosynthesis (123), Ocean Uptake (92). Total Outflow = 215 GtC/yr. The net flux is Inflow - Outflow = 219 - 215 = +4 GtC/yr. Since the net flux is positive, the atmosphere is accumulating carbon. A is incorrect because the system is not in steady state. B is incorrect because the net flux is into the oceans (92 uptake vs 90 release). C is incorrect as Photosynthesis (123) and Respiration (120) are much larger fluxes than fossil fuels (9).

Question 15

1. The 'Marine Biota' carbon reservoir will decrease due to the toxic effects of excessive nutrients.
2. The flux of CO₂ from the atmosphere to the ocean will decrease as phytoplankton are inhibited by the colder, upwelled water.
3. The 'Marine Biota' carbon reservoir and the flux of carbon to the 'Deep Ocean' via sinking organic matter will both increase. (correct answer)
4. The 'Dissolved CO₂' reservoir in the surface ocean will increase as the upwelled water releases stored carbon.

Explanation: Nitrogen and phosphorus are often limiting nutrients for phytoplankton growth in the surface ocean. An increased flux of these nutrients (from upwelling) will stimulate photosynthesis. This leads to a phytoplankton bloom, which increases the size of the 'Marine Biota' carbon reservoir. As these organisms die, they sink, increasing the flux of organic carbon to the deep ocean (the biological pump). While upwelled water can release CO₂, the biological response is typically dominant and leads to a net drawdown of CO₂, strengthening the ocean sink.

Question 16

1. The pollutant concentration in the lake will increase, which in turn will increase the mass leaving via the outflow flux until outflow once again balances inflow. (correct answer)
2. The volume of the lake will have to increase to accommodate the extra pollutant, diluting it until the original concentration is restored.
3. The outflow flux rate (in m³/day) will spontaneously increase to exactly 5 kg/day to remove the added pollutant and maintain a stable concentration.
4. The pollutant will be permanently sequestered in the lake sediments, so the concentration in the water will not change, but the sediment reservoir will grow.

Explanation: When the inflow of the pollutant increases, the total mass of the pollutant in the lake reservoir begins to rise, increasing its concentration. The outflow flux of the pollutant is a product of the water outflow rate (which is constant) and the pollutant concentration in the lake. Therefore, as the concentration increases, the mass of pollutant leaving the lake per day also increases. This process continues until the concentration is high enough that the outflow flux equals the new, higher inflow flux, at which point a new, higher-concentration steady state is reached.

Question 17

1. Denitrification, the conversion of soil nitrates to N₂ gas.
2. Leaching, the loss of dissolved nitrates from the soil into groundwater.
3. Nitrogen Fixation, the conversion of atmospheric N₂ into ammonia. (correct answer)
4. Nitrification, the conversion of ammonium to nitrates by soil bacteria.

Explanation: The diagram shows the internal recycling of nitrogen between plants and soil, but it lacks an input from the largest nitrogen reservoir, the atmosphere. Nitrogen fixation is the only natural process that converts inert atmospheric nitrogen gas (N₂) into a form (ammonia) that can enter the biological pathways. Without this flux, the ecosystem would eventually lose its nitrogen through processes like denitrification and leaching, and it would not be sustainable. Denitrification and leaching are loss pathways from the ecosystem. Nitrification is an internal conversion, not an input from the atmosphere.

Question 18

1. A long-term increase in the sulfur concentration of the 'Ocean' reservoir, leading to ocean acidification.
2. An increase in the 'Weathering of Rocks' flux as acid rain dissolves continental crust.
3. The formation of sulfate aerosols in the stratosphere, which increases planetary albedo and causes a temporary cooling effect. (correct answer)
4. A strengthening of the flux from 'Marine Biota' to the atmosphere, as plankton release more dimethyl sulfide (DMS) in response.

Explanation: When a large volcanic eruption injects SO₂ into the stratosphere, it reacts with water vapor to form tiny droplets of sulfuric acid, or sulfate aerosols. These aerosols are highly reflective to incoming solar radiation. This increase in reflectivity (albedo) of the atmosphere reduces the amount of solar energy reaching the surface, leading to a net cooling effect that can last for 1-3 years. While some SO₂ contributes to acid rain (implying B), the primary and most significant short-term global effect is climate-related. Effects on the ocean reservoir (A) are minor and long-term. A response from marine biota (D) is not a direct or primary consequence.

Question 19

1. Leakage has no effect on the atmospheric reservoir because the carbon is simply transferred between two forest reservoirs.
2. The net reduction of atmospheric carbon is less than intended because the leakage flux releases carbon that would have otherwise remained stored. (correct answer)
3. Leakage results in a greater reduction of atmospheric carbon because newly deforested areas are often less carbon-dense than protected forests.
4. The atmospheric carbon reservoir actually increases because the process of protecting one forest requires significant fossil fuel emissions.

Explanation: The intended outcome of protecting Reservoir A is to prevent a flux of carbon from the forest to the atmosphere. Let's say this prevents X tons of C from being emitted. However, the policy causes a 'leakage' flux, where Y tons of C are emitted from Reservoir B instead. The actual net change in emissions is (Y - X). Since deforestation is shifted, not eliminated, Y is a positive value, offsetting the gains from protecting A. The net reduction in atmospheric carbon input is smaller than the amount of carbon preserved in Reservoir A. Therefore, the leakage flux diminishes the effectiveness of the policy.