EQ1- How does the carbon cycle operate to maintain planetary health

Question 1

What is the importance of the carbon cycle on earth

Answer 1

Provides a major building block for all life on earth. A balanced carbon cycle is important in regulating our climate and maintaining the health of our planet.

Question 2

Explain the composition of carbon

Answer 2

Is a common element in the composition of the earth
Exists in gas, solid and liquid forms , in organic and inorganic forms. Carbon moves between these forms (carbon pathway) through natural (biogeochemical) processes over time

Question 3

Define Sequestering

Answer 3

Is the natural storage of carbon by physical or biological processes such as photosynthesis

Question 4

Explain the carbon cycle as a system

Answer 4

The carbon cycle is a closed system . It does not have any external inputs or outputs , so the total amount of carbon is constant and finite

Question 5

Define stores

Answer 5

Reservoirs where carbon is held

Question 6

Define Fluxes

Answer 6

Are the movement of carbon between stores

Question 7

Define processes

Answer 7

Are the physical mechanisms which drive the fluxes between stores

Question 8

Define and explain the form of the four carbon stores

Answer 8

The atmosphere - gases such as carbon dioxide and methane

The hydrosphere - dissolved carbon dioxide in oceans and lakes

The lithosphere - carbonates in limestone and fossil fuels

The biosphere - living and dead organisms

Question 9

State the largest Carbon store and the largest carbon flux

Answer 9

Carbon store - sedimentary rock store (83 million pgc)

Carbon flux - photosynthesis (123 pgc/year)

Question 10

Explain the geological carbon cycle

What is its importance

Answer 10

Is a natural cycle that moves carbon between land, oceans and the atmosphere. This movement involves chemical reactions which creates stores to trap carbon, leading to a natural balance between carbon production and absorption within the cycle, allowing a equilibrium.

Question 11

Explain the factors in the geological carbon cycle

Answer 11

Carbon held within the mantle is released as co2 when volcanoes erupt

Co2 in the atmosphere combines with rainfall to produce acid rain

Carbonic acid reacts with rocks to form calcium carbonate

When plants and animals die their shells form limestone with carbon stored in it

Carbon rich rocks are sub ducted along plate boundaries

Question 12

Explain the biogeochemical carbon cycle

What is its importance

Answer 12

The cycles processes determine how much of the carbon available on earth is stored or released. Living organisms help control the balance between storage, release, transfer and absorption. Allows an equilibrium to be maintained

Question 13

Explain the factors of the biogeochemical carbon cycle

Answer 13

Photosynthesis occurs where plants remove co2 from the atmosphere

Respiration occurs where animals consume plants and release co2 into the atmosphere and water

Decomposition occurs in dead plants and animals releasing co2 into soils and deposits carbon in the sea

Combustion occurs where fossil fuels are burnt releasing co2

All contribute towards co2 in the atmosphere

Question 14

Define system feedback

Answer 14

Occurs when the earth’s system operate by negative feedback , maintaining an equilibrium by preventing too much release of co2 into the atmosphere

Question 15

Explain the impact of human carbon emissions

Answer 15

Are only small compared to natural emissions. However when more carbon is released into the atmosphere , through human activities, it adds up because the land and ocean cannot absorb all the extra carbon. Human emissions disrupt the natural balance of the carbon cycle

Question 16

Explain which areas of the world absorb the most co2

Answer 16

Mid and high latitudes absorb the most carbon dioxide. In the northern hemisphere levels of CO2 a higher due to the high amount of vegetation, allowing photogenic activity to occur. In the northern hemisphere large fluctuations in co2 occur during summer and winter due to the large differences in plant photosynthesis

Question 17

State the three forms of carbon and where they are found

Answer 17

Inorganic - found in rocks as carbonates
Organic- found in plant material
Gaseous- found as C02, methane and carbon monoxide

Question 18

Explain how limestone rock is a store for carbon

Answer 18

Contains a high concentration of calcium carbonate, formed from shell building organisms (coral) that extracted carbon from the seawater, and also from marine phytoplankton that absorbs carbon through photosynthesis

Their remains accumulate on the ocean floor, and after a long period of time are cemented and lithified into limestone

Question 19

Explain how biologically derived carbon in rocks is a store for carbon

Answer 19

An example is shale

Formed when carbon from organisms is embedded into layers of mud. Heat and pressure over millions of years compress the mud and carbon to form shale rock

Question 20

Explain how carbon fossil fuels is a store for carbon

Answer 20

Made up 300 million years ago from dead organic material

Dead organisms sank to the bottom of rivers and seas, covered in silt and mud, then decayed anaerobically

The organic matter built up faster than it decayed , forming fossil fuels like coal instead of shale

Question 21

State the two main geological processes that release carbon into the atmosphere

Answer 21

Chemical weathering in rocks

Volcanic degassing at ocean ridges and subduction zones

Question 22

Explain how chemical weathering in rocks is a process that releases carbon into the atmosphere

Answer 22

Occurs where the geological part of the carbon cycle reacts with the rock cycle, causing the weathering of carbon rich rocks, like limestone

Water reacts with atmospheric carbon, forming carbonic acid.

Only weakly acidic , but dissolves rock minerals (when it reaches the surface as rain) to form new minerals such as calcium carbonate. Only occurs when calcium ions are transported to the sea, where it reacts with bicarbonate to form calcium carbonate.

These minerals are Deposited and buried , then cemented and liquefied after a long period of time to form limestone

Tectonic spreading occurs, causing the seduction of the sea floor and bringing carbon rich sedimentary rocks into contact with extreme heat, in the form of magma. This causes chemical changes and rock to be degassed , releasing CO2 into the atmosphere.

This is seen in contemporary society , in geothermal areas like Iceland and New Zealand

Question 23

Explain how volcanic degassing at ocean ridges and subduction zones is a process that releases carbon into the atmosphere

Answer 23

Is relatively insignificant in comparison to human activity , however it does release approximately 300 million tons of carbon into the atmosphere, due to it being the least soluble and his degassed earlier in the eruption process.

Outguessing takes place in subduction zones and ocean ridges seen in Hawaii and Cicely. Degassing occurs in the vent of a of a volcano, where carbon is recycled at subduction zones and carbonate rocks are dragged into the mantle. In the volcano erupts magma, containing carbon , is released into the atmosphere

Question 24

Explain the oceans role in the carbon cycle

Answer 24

The ocean is one of the earth’s largest carbon stores, 50x greater than the atmosphere

Question 25

Define carbon sequestration

Answer 25

Is the removal and storage of carbon from the atmosphere. Usually occurs in oceans, forests and soil through photosynthesis.

Question 26

Describe the co2 gas exchange between the ocean and the atmosphere

Answer 26

Operates over several hundreds of years. Only a small proportion of the carbon in oceans is eventually buried in the ocean sediments.

Question 27

Define carbon cycle pumps

Answer 27

Are the processes operating in oceans to circulate and store carbon. There are three types: biological, carbonate and physical.

Question 28

Define and explain the biological pump in oceans

Answer 28

Is the organic sequestration of CO2 to oceans by phytoplankton.

Phytoplankton float up to the ocean surface to photosynthesise, they are the base of the food web.
Carbon is then passed up the food chain by fish and zoo plankton, which releases CO2 back into the water and the atmosphere.
Most carbon is recycled in surface water, only 0.1% reaches the sea floor after the dead plankton sink and decompose.

Question 29

Define and explain the carbonate pump in the ocean

Answer 29

Is the formation of sediments from dead organisms.

Marine organisms (like plankton, oysters and lobsters) may utilise calcium carbonate to make hard outer shells.
When organisms die and sink, their shells dissolve before reaching the sea floor. The carbon becomes part of the deep ocean current.
Shells that don’t dissolve build up slowly on the sea floor, forming limestone sediments like the white cliffs of dover

Question 30

Define and explain the physical pump in the ocean

Answer 30

Is the ocean circulation of water including upwelling, downwelling and the thermohaline current.

Co2 concentration is different in different parts of the ocean, the colder the water the more potential for co2 to be absorbed whilst warm waters release co2 into the atmosphere.
Major ocean currents, like the gulf stream, moves water from the tropics to the poles, the water cools and absorbs more atmospheric carbon.

Question 31

Define and explain thermohaline circulation in the ocean

Answer 31

Is the global system of surface and deep ocean currents driven by temperature (thermo) and salinity (haline) differences between areas of the ocean.

1. Main current begins in polar oceans with low temperatures and high levels of salinity
2. Division of the main current sees a current in the Indian ocean and the Pacific ocean
3. The two currents warm and rise, circulating around the world until they reach the poles

Question 32

Explain and define the role of primary producers (plants) in the carbon cycle

Answer 32

Sequester carbon through photosynthesis. Store a significant amount of carbon.

Producers are green plants that use solar energy to produce biomass, accounting for 95% of a trees biomass. As they grow they release co2 into the atmosphere through respiration

Question 33

Explain the role of consumers in the carbon cycle

Answer 33

Depend on producers to feed, plants and leaves dropped from trees, and return carbon to the atmosphere through respiration.

These consumers store carbon as part of their fats and proteins.

Dead animals and plants Start to decompose fastest in tropical climates, where there are high temperatures and high rainfall, and biological decomposes feed on the dead organisms. When decomposition occurs the nutrients and carbon are taken in by the soil, acting as a store and contributing towards the growth of biomass

Question 34

Explain the significance of soil in the carbon cycle

Answer 34

Soil stores 20 to 30% of global carbon, sequestering two times the quantity of carbon as the atmosphere.

After the death of organisms thousands of compounds are decomposed before being broken down by soil microbes and released back into the atmosphere.

Carbon cycling is most active in the top of the soil, and perms first region 60% of carbon is stored in 30 cm.

Mangrove forests sequester 1.5 metric tons of carbon a year, with thick layers of peat which absorbs carbon and decompose it slowly. Carbon from mangrove soil is only released if it is drained.

Question 35

Define biological carbon

Answer 35

Is stored in soils in the form of dead organic matter, or returned back to get atmosphere as a result of decomposition

Question 36

Explain the factors affecting social capacity to store carbon (3)

Answer 36

Climate- dictates plant growth and microbial activity, rapid decomposition occurs in hot climates with high rainfall

Soil type- Clee rich soils have a higher carbon content than sandy soil,protecting carbon from decomposition.

Management and use of soil- cultivation and disturbance has caused a 40- 90 billion tonne loss of carbon since 1850.

Question 37

Define systems

Answer 37

Is how the carbon cycle sustains other earth systems

Question 38

Define equilibrium of carbon

Answer 38

Describes how the carbon cycle is balanced and how that balance is disturbed by human activities

Question 39

Explain the greenhouse effect

Answer 39

Is the warming of the atmosphere as gases such as carbon dioxide, methane and water vapour absorb heat energy radiated from the earth. These greenhouse gases absorb and reflect back some of the radiated heat from the earth’s surface , helping to retain a temperature to support human life.

Question 40

Explained the enhanced greenhouse effect

Answer 40

Describes the increase of greenhouse gases in the atmosphere as a result of increased human activity. The burning of fossil fuels and deforestation release natural stores of carbon to form co2 and nitrous oxide , leading to increased water temperatures and the trapping of heat in the atmosphere.

Question 41

Describe the effect of greenhouse gases on temperature.

Answer 41

The amount of solar energy reaching the earth’s surface varies at different locations, which influences temperature.

The angle of the sun’s rays makes solar insolation intense at the equator, but dispersed over the poles. How light or dark an area is on the earth’s surface determines the albedo, snow reflects and dark forests absorbs.

Heat is redistributed around the world by wind, ocean currents and pressure differences

Question 42

Describe the effect of greenhouse gases on precipitation

Answer 42

The heating of the earth’s atmosphere and surface controls the temperature, pressure, movement and moisture content of the air.
Where solar insolation is most intense, over the equator, precipitation is more intense due to the rising, cooling and condensing of cool air

Question 43

Explain and list the role of photosynthesis in regulating the composition of the atmosphere

Answer 43

Phytoplankton in the ocean sequester co2 through photosynthesis, the biological carbon pump

Terrestrial photosynthesis enables plants to sequester, the released back into the atmosphere through respiration and decomposition.

Tropical rainforests and coral reefs sequester large amounts of carbon

Question 44

What is the importance of carbon for soil (4)

Answer 44

Supports micro-organisms that maintain the nutrient cycle
Breakdown organic matter
Provide pore spaces for infiltration and storage of water
Enhance plant growth

Question 45

What are the characteristics of healthy soil (6)

Answer 45

Dark , crumbly and porous
Contain many organisms 
Provide air, water and nutrients for micro-organisms 
Contains and sequesters carbon
Enable infiltration and percolation
Retains moisture