1 - The Carbon Cycle

Question 1

What is the carbon cycle?

Answer 1

Carbons route on Earth, within which carbon is transformed from organic carbon (in living organisms) to inorganic carbon (ores and minerals) and back again.

Question 2

Name the 7 carbon stores (FALSBOS)

Answer 2

1. Fossil fuels
2. Atmosphere
3. Lithosphere
4. Soils
5. Biosphere/vegetation
6. Oceans
7. Sediments on the ocean floor

Question 3

Name the 7 carbon flows.

Answer 3

1. Photosynthesis
2. Combustion
3. Ocean uptake and loss
4. Sequestration
5. Respiration
6. Decomposition
7. Weathering

Question 4

Describe the 3 main carbon forms.

Answer 4

Carbon Dioxide (CO2) - gas found in the atmosphere, soils and oceans.
Methane (CH4) - gas found in the atmosphere, soil, oceans and sedimentary rock.
Calcium Carbonate (CaCO3) - a solid compound found in calcareous rocks, oceans and in skeletons and shells of ocean features.

Question 5

Give an example of positive feedback in the carbon cycle.

Answer 5

Increase in global temp. > Oceanic temp. increases > Dissolved CO2 released by oceans > More CO2 in atmosphere > Increase in global temp. …

Question 6

Give an example of negative feedback in the carbon cycle.

Answer 6

More fossil fuels burnt > Increase of CO2 in the atmosphere > Increased global temp. > More vegetation grows > More CO2 taken in by plants > Reduced CO2 in atmosphere > Global temp. ‘dampens’ due to less atmospheric CO2

Question 7

Describe the different time scales that carbon flows happen over.

Answer 7

The fastest carbon flows (minutes-days) include photosynthesis, respiration, combustion and decomposition.

The slowest carbon flow (millions of years!) is sequestration.

Question 8

Describe the different spatial scales that carbon flows happen over.

Answer 8

Plant scale = photosynthesis and respiration

Ecosystem scale = Combustion and decomposition

Continental scale = all flows!!

Question 9

Explain photosynthesis as a carbon flow.

Answer 9

Transfers carbon from the atmosphere to the biosphere.

Energy from sun + CO2 + H2O -> Glucose + O2

Tiny marine plants (phytoplankton) in the sunlit waters of the oceans, as well as all terrestrial plants, photosynthetic algae, and bacteria turn carbon into organic matter by photosynthesis.

Question 10

Explain decomposition as a carbon flow.

Answer 10

Transfers carbon from the biosphere to the atmosphere and soil.

This is when the majority of the remainder of carbon left in living things when they die is released by decomposers that break down the cells and tissues in dead organisms.

Question 11

Explain respiration as a carbon flow.

Answer 11

Transfers carbon from the biosphere to the atmosphere.

Glucose + O2 -> CO2 +H2O + Energy

By the process of respiration, plants use some stored carbohydrates as an energy source to carry out their life-functions.

Question 12

Explain combustion as a carbon flow.

Answer 12

Transfers carbon from the biosphere to the atmosphere.

Combustion is the burning of living and dead things e.g. wildfires which are naturally caused by lightning strikes but can also be due to humans.

Question 13

Explain carbon sequestration as a carbon flow.

Answer 13

Transfers carbon from an environment (the atmosphere or the hydrosphere) and to new store (the biosphere, lithosphere, sediments on the ocean floor, or an artificial store)

Sequestration is the trapping of carbon and its isolation in a natural or artificial store.

Example:
Atmospheric CO2 is removed and dissolved in water = CaCO3, reaches Earth as rain and dissolves minerals on Earth’s surface through chemical weathering, releasing ions that are carried by surface waters into the oceans and settle out as minerals that marine organisms use in shells and coral. These creatures die and their skeletons sink to the bottom of ocean, are buried for millions of years and become sedimentary rock. Through subduction, CO2 can be released back into the atmosphere from this rock.

Carbon sequestration can also happen in plants but is released much quicker when plants combust or decompose.

Question 14

Explain weathering as a carbon flow.

Answer 14

Transfers carbon from the lithosphere to the hydrosphere.

Weathering is the breakdown or decay of rocks by mildly acidic carbonic acid when rainwater absorbs CO2. The carbon in rocks is held in a solution as the rock dissolves and is transported by the water cycle to the oceans.

Question 15

What are the 2 types of changes in the carbon cycle?

Answer 15

Natural variations
Human impacts

Question 16

What are the 2 main natural variations that create change in the carbon cycle?

Answer 16

Wildfires and volcanic activity.

Question 17

What are the 3 main human impacts that create change in the carbon cycle?

Answer 17

Farming practices, land-use change (deforestation and urbanisation), and hydrocarbon extraction + burning (fossil fuels)

Question 18

What are the effects of wildfires as a natural variation that creates change in the carbon cycle? (Short and long term)

Answer 18

Short term:
They rapidly transfer large quantities of carbon from biomass or soil to the atmosphere = more carbon in atmosphere
Loss of vegetation = decrease in photosynthesis = less CO2 removed from the atmosphere = more carbon in atmosphere

Long term:
Fires can encourage the growth of new plants = increase in photosynthesis = less carbon in atmosphere.

Fires therefore can have a neutral effect on the amount of atmospheric carbon.

Question 19

Fill in the blanks: What are the effects of volcanic ____ as a natural variation that creates change in the carbon cycle?
United ____ geological ____: CO2 released from volcanic ____ “has never caused ____ global warming of the planet”
541-251 ____ years ago volcanoes were much more ____.
Recent eruptions haven’t released enough ____ from the lithosphere to the ____ to make any real ____
Volcanic eruptions can actually ____ global temp…
- sulphuric ____ emitted counterbalances emitted CO2 and increases ____ of solar radiation.
- eruptions release ____ into the atmosphere = block incoming solar radiation.

Answer 19

activity, states, survey, eruptions, detectable, million, active, CO2, atmosphere, difference, reduce, acid, reflection, ash

Question 20

What are the effects of farming practices as a human impact that creates change in the carbon cycle?

Answer 20

Ploughing, harvesting, rearing livestock, using machinery fuelled by FF and using fertilisers based on FF all release carbon!

Livestock, especially cattle, ruminate which produces CH4 as a by-product. Cattle in USA emit 5.5 million tonnes of CH4 per year…20% of total USA CH4 emissions.

CH4 is also produced in the cultivation of rice. Rice may contribute up to 20% of global CH4 production and is the primary food source for 50% of the world’s population.

Question 21

What are the effects of land-use change as a human impact that creates change in the carbon cycle?

Answer 21

Deforestation: when def. by burning occurs, carbon is immediately released and if the land is then used for a different purpose the future absorption of CO2 from the atmosphere by new vegetation will be reduced. The system has become a carbon source rather than a carbon sink.

Urbanisation: rural areas -> urban areas = replaces vegetation and covers up soil which are both important carbon stores with impermeable surfaces. Urban areas are a major source of carbon emissions…transport, industry, conversion of land use and cement manufacturing. Highest polluting cities = Seoul, Guangzhou, New York, Hong Kong, Los Angeles.

Question 22

What are the effects of hydrocarbon extraction and burning (fossil fuels) as a human impact that creates change in the carbon cycle?

Answer 22

Fossil fuels are important long-term carbon stores. Most of the world’s oil and gas is extracted from 70-100 million year-old rocks. When burnt, stored carbon is released, primarily as CO2, into the atmosphere, accelerating the carbon cycle. FF burning accounts for 80% of all human induced carbon emissions.

Question 23

Budget = looks at the relationship of the inputs and outputs of a system

What is the carbon budget?

Answer 23

How much carbon is emitted by various processes compared to what can be absorbed by nature or captured by people.

Question 24

Give 2 examples of a carbon budget.

Answer 24

Trees hold more carbon in the day due to the process photosynthesis, and less carbon at night due to the process respiration.

Deciduous forests hold more carbon in the summer as there is more vegetation, and less carbon in the winter due to less vegetation (drop leaves!!)

Question 25

What is the main cause of change in levels of atmospheric carbon?

Answer 25

The enhanced greenhouse effect:
Human activity is driving temp. up due to huge use of fossil fuels that is releasing GG into the atmosphere, trapping heat near the Earth. Evidence includes a string of very warm years with 2023 as the warmest year in measured history.

Question 26

Fill in the blanks: What are the impacts of the changing carbon cycle on _ ?

1. Warmer ___ = increased plant ___ and growing ___ = more ___ = more water needed.
2. Farmland in mid-___ regions have been ___ = increase in CO2 uptake as farmland is replaced by ___ which store much more carbon than ___.
3. Warmer = drier = more ___.
4. In tundra, warmer land = increased rate of ___ of dead ___ matter = more ___ = more atmospheric ___ = warmer ___. = permafrost ___ = release more CO2!!

Answer 26

temp, growth, seasons, evapotranspiration

latitude, abandoned, vegetation/trees, crops

wildfires.

decay, organic, decomposition, CO2, temp, melts

Question 27

What are the impacts of the changing carbon cycle on the ocean?
Fill in the blanks:
1. Ocean ___: when CO2 dissolves into ocean it makes the ocean less ___ = coral reefs and ___ species have less carbonate available so cannot build strong ___ = coastal communities lose ___ source, livelihood ___ and reduced capacity to buffer storm ___.

Answer 27

acidification, alkaline, planktonic, shells, food, security, surges

Question 28

What are the impacts of the changing carbon cycle on the ocean?
Fill in the blanks:
2. Ocean ___: absorb heat from ___ = phytoplankton will ___ = oceans ability to absorb carbon ___ is limited.

Answer 28

warming, atmosphere, decrease, biologically

Question 29

What are the impacts of the changing carbon cycle on the ocean?
Fill in the blanks:
3. Melting sea ___ = positive ___!…ice melts -> reflective ice is replaced by heat ___ water -> ocean absorbs ___ -> water temps ___ -> ice ___! = ice bound algae is lost and polar bears cannot ___ on sea ice to get food (seals) AKA ___ chain is affected.

Answer 29

ice , feedback, absorbent, heat, rise, melts, travel, food

Question 30

What are the impacts of the changing carbon cycle on the ocean?
Fill in the blanks:
4. ___ salinity: decreasing due to high levels of ___ and ___ temp. = changes in salinity ___ ___ the oceanic circulation in the North-East ___… affects UK ___.

Answer 30

ocean, precipitation, high, slows down, Atlantic, climate

Question 31

What are the impacts of the changing carbon cycle on the ocean?
Fill in the blanks:
5. Sea levels ___: ___mm per year since 19__s due to melting ice sheets and thermal ___ of water

Answer 31

rise, 3.5, 90, expansion