The carbon cycle Flashcards
What is the carbon cycle ?
The cycle by which carbon moves from one Earth sphere to another.
A closed system.
What are the major stores of carbon ?
-Lithosphere
-Cryosphere
-Atmosphere
-Hydrosphere
-Biosphere
Explain the lithosphere as a store of carbon
The crust and upper mantle.
Inorganic forms of carbon in the lithosphere: Ca, Mg
Organic forms : Coal, oil, organic matter, natural gas
-Distributed between marine sediments, sedimentary rock, soil organic matter, fossil fuel deposits, peat.
-Sedimentary rock is the largest store containing 99.9% of carbon
-In total stored around 100 million Gt of carbon
Explain the Cryosphere as a store of carbon
-Methyl clathrates are molecules of methane that are frozen into ice crystals (form under high pressure and low temperature)
-Organic matter frozen in permafrost (global warming melts permafrost releasing CO2/methane)
-Permafrost is in the Northen Hemisphere
Explain how the atmosphere is a store of carbon ?
Atmosphere used to composed of mainly CO2.
-Carbon makes up 0.04% of the atmosphere
-Due to human activities CO2 conc is higher than is has been for at least 800,000 years (possibly 200 million)
Explain the hydrosphere as a store of carbon
-Oceanic store between 37,000 GtC and 40,000 GtC
-Euphotic zone (surface) 900 GtC
-Twighlight zone (intermediate) 37,100 GtC
-Living organic matter amounts 30 GtC and dissolved organic matter 700 GtC
-Carbon stored by sedimentation
Explain how the biosphere is a store of carbon
The total sum of all living matter.
-living vegetation
plants constantly exchange carbon with the atmosphere
-Plant litter
Fresh, undecomposed plant debris
-Soil humus
Litter decomposition, gets dispersed throughout the soil
-Peat
Accumulation of partially decayed vegetation in wetland conditions, anaerobic conditions which slows down decomposition
-Animals
Decomposition
What is a Lithosere ?
A community that forms on rocks
What is a Psammosere ?
A community that forms on sand
What is a Xerosere ?
A community that forms on a dry and arid area
What is a Halosere ?
A community that forms on a marshy and saline area
What is the fast carbon cycle ?
Relatively rapid transfers of carbon compounds over years, decades and centuries
What is the slow carbon cycle ?
Transfers of carbon compounds over extensive timescales (up to millions of years)
What processes are apart of the slow carbon cycle ?
-Weathering
-Oceanic carbon pump
-Burial of sediment
-Carbon sequestration
-Tectonic/volcanic activity
What processes are apart of the fast carbon cycle ?
-Photosynthesis
-Respiration
-Decomposition
-Combustion
Explain decomposition
-Returns carbon from the biosphere to atmosphere. (can end up in pedosphere - soils or lithosphere)
-Decomposers (e.g. fungi, bacteria, earthworms) break down dead organisms and return carbons in their bodies to the atmosphere as CO2 by respiration.
-Dead organisms are broken down into substances that plants need for growth.
-Decomposition can be blocked if organic matter is frozen or buried in anaerobic environments (peat)
Explain combustion
-When organic material is burned in the presence of oxygen and gives off CO2 , water and energy
-Oil, coal, fossil fuel, wood, plastic
-If any other elements are present they combine with oxygen to form pollutant molecules (e.g. nitrogen oxides)
-Could be deliberate and man-made or natural wildfires
Explain sediment burial
-Tiny marine organisms from skeletons and shells of calcium carbonate
-When they die they sink
-Over years they’re buried by layers of sediment, as the pressure builds they turn into sedimentary rock
-Carbon is then stored as rocks beneath the ocean
Explain weathering
-CO2 is removed from the atmosphere when it dissolves in the ocean and forms carbonic acid
-This forms acid rain which reacts with minerals dissolving them into ions
-The ions then reach rivers and eventually ocean where they eventually form calcium carbonate
Explain tectonic and volcanic process
-Circulation of magma drags plates which causes oceanic and continental crust to meet
-The oceanic plate subducts, heats, rises back to the surface through eruptions, vents and CO2 rich hot springs.
-This allows CO2 to return to the atmosphere
Explain the physical ocean pump
-CO2 dissolves in the sea (in colder water-poles)
-The cold water sinks to the bottom (vertical deep mixing)
-Once the cold water reaches the equator, the water warms and rises which releases CO2 back to the atmosphere
-Water then moves back to the poles at surface to repeat process
Explain the biological carbon pump
-CO2 dissolves in the oceans
-This carbon is used to create shells and skeletons for marine organisms as calcium carbonate
-As they die they sink, the decay releases CO2 in the deep water
-Some material sinks and forms sedimentary rocks
Explain geologic carbon sequestration
-Carbon is captured at its source (factory) and injected in liquid form into stores underground
-Injected into depleted oil, gas reservoirs, coal seams, salt formations or the deep sea
-This is still at the experimental stage and is very expensive
Explain terrestrial carbon sequestration
-CO2 is absorbed by plants
-Therefore enrichment of plant ecosystems is a positive environmental action
-However forests may lose carbon to a fire or disease
-It’s slow growing and requires active management
-Carbon is never permanently removed from the atmosphere
