The carbon cycle

• What is carbon and where is it stored?

  • an element
  • organic and inorganic stores
• How much carbon is stored in the pedosphere?

  0.003%
• How much carbon is stored in the atmosphere?

  0.001%

  stored as carbon dioxide and methane
• How much carbon is stored in The biosphere?

  0.004%
• How much carbon is stored in the cryosphere?

  less than 0.01%

  most is stored in permafrost
• How much carbon is stored in the hydrosphere?

  0.04%
• How much carbon is stored in the lithosphere?

  over 99.9% in sedimentary rocks

  0.004% in fossil fuels
• What are examples of carbon forms found in the lithosphere?

  sedimentary rocks, organic carbon, fossil fuels and marine sediments
• What are examples of carbon forms found in the hydrosphere?

  carbonate ions, bicarbonate ions and dissolved carbon dioxide
• What are examples of carbon forms found in the pedosphere?

  soil organisms and plant remains
• What are examples of carbon forms found in the cryosphere?

  frozen mosses
• What are examples of carbon forms found in the atmosphere?

  gaseous carbon
• What are examples of carbon forms found in the biosphere?

  living plants and animals
• Where are the largest stores of carbon found globally and why?

  • equatorial regions such as South America, central Africa and East Asia
  • rainforest environments are found here so more photosynthesis
• What is the carbon cycle?

  the process by which carbon is stored and transferred
• What type of system is the carbon cycle?

  closed
• What are examples of carbon flows?

  photosynthesis, respiration, combustion, decomposition, ocean uptake and loss, weathering, sequestration
• Describe photosynthesis as a carbon flow?

  transfers carbon stored in atmosphere to biomass, carbon is passed through food chain and released through respiration and decomposition
• Describe respiration as a carbon flow?

  transfers carbon from living organisms to the atmosphere
• Describe combustion as a carbon flow?

  transfers carbon stored in living, dead or decomposed biomass to the atmosphere by burning
• Describe decomposition as a carbon flow?

  transfers carbon from dead biomass to atmosphere and soil
• Describe ocean uptake and loss as a carbon flow?

  co2 is dissolved from the atmosphere into the ocean
• Describe weathering as a carbon flow?

  Transfers carbon from atmosphere to hydrosphere and biosphere

  Atmospheric carbon reacts with water vapour to form acid rain which dissolves rocks. These molecules are washed into the sea to react with co2 in water to form calcium carbonate which sea creatures make shells with
• Describe sequestration as a carbon flow?

  carbon from the atmosphere can be captured in sedimentary rocks or as fossil fuels as dead material is compacted on the ocean floor
• What is a fast carbon flow?

  carbon flows quickly transfer carbon between sources - in minutes, hours, or days
• What are examples of fast carbon flows?

  Photosynthesis, respiration, decomposition, combustion
• What are examples of slow carbon flows?

  sequestration, conversion of ocean sediments into carbon rich rock
• How does volcanic activity increase carbon inputs ?

  carbon stored in magma is released during volcanic eruptions - recent volcanic eruptions have released less co2 than human activities however there is the potential for a very large eruption to disrupt the cycle significantly
• How do wildfires increase carbon inputs?

  rapidly transfer large quantities of carbon from biomass to the atmosphere

  long term - fires can encourage new plant growth - photosynthesis
• How does hydrocarbon fossil fuel increase inputs of carbon dioxide?

  extraction and combustion of fossil fuels releases co2, without human intervention the carbon would be sequestered in the lithosphere for millions of years
• How does deforestation increase co2 inputs?

  clearance reduces the size of the carbon store, if the cleared forest is burned there is a rapid flow of carbon from the biosphere to the atmosphere
• How do farming practices increase carbon inputs in the atmosphere?

  • animals release co2 and methane when they respire and digest food
  • ploughing can release co2 stored in soil
  • growing rice increases methane
• How do land use changes increase carbon inputs in the atmosphere?

  • vegetation is removed to make way for buildings - reduces carbon storage in biosphere
  • concrete production releases co2
• How does melting tundra increase carbon in the atmosphere?

  global warming resulting in melting tundra releasing co2
• What natural factors reduce the removal of carbon in the atmosphere?


  glacial periods (less vegetation), interglacial period (warmer oceans absorb less co2), winter in northern hemisphere (biomass shuts down)
• What human factors reduce the removal of carbon from the atmosphere?

  clearing vegetation, climate change resulting in warmer oceans
• What natural factor reduces carbon inputs into the atmosphere?

  long term reduction of volcanic activity
• What human factors reduce inputs of carbon?

  mitigation strategies such as carbon capture schemes
• What natural factors remove more carbon from the atmosphere?

  • glacial periods (cooler oceans absorb more co2)
  • interglacial period (more vegetation)
  • summers in northern hemisphere (increased biomass activity)
• What human factors increase removal of carbon from the atmosphere?

  reforestation and afforestation projects