6.1 - Carbon and the geological cycle

• Carbon

  • Regulates climate to provide warmth
  • Stored in rocks, plants and oceans
  • These are referred to as pools, stocks and reservoirs
  • Three types:
  • Terrestrial
  • Oceanic
  • Atmospheric
  • Flux is the transfer between stores
• Terrestrial carbon store

  • Sedimentary rocks have high concentrations e.g. limestone contains 42% calcium carbonate
  • Geological processes trap carbon in the form of coal, oil and gas
  • Calcareous oozes are found under the South Pacific, Atlantic and Indian Oceans, ready to be turned into limestone rocks
• Atmospheric carbon store

  • Volcanic activity, respiration, wildfires and outgassing emit CO2 (only 0.03%)
  • Small changes in concentration affect global temperatures
• Oceanic carbon store

  • CO2 is dissolved by oceans from the atmosphere
  • Most CO2 is stored in intermediate and deep waters (only 2.5% in surface waters)
• The Biogeochemical carbon cycle

  • Consists of 3 carbon stores: terrestrial, oceanic and atmospheric
  • Annual fluxes between stores measured in Pg (petagram) or Gt (gigaton) (both are equal to 1 billion tons)
  • Living organisms are the key part
  • Control balance between storage, release, transfer and absorption
• Biogeochemical carbon cycle

  1. Photosynthesis - plants remove CO2 from atmosphere
  2. Respiration - animals consume plants and release CO2 into the atmosphere and water
  3. Decomposition - the decomposition of dead plants and animals releases CO2 into soils and deposits carbon on the sea floor
  4. Combustion - burning fossil fuels releases CO2 into the atmosphere
• Geological carbon cycle

  • CO2 loss to air due to calcium carbonate deposition
  • CO2 and rain combine to form acidic rain (carbonic acid)
  • CO2 released via volcanic outgassing