Carbon EQ1 Flashcards
Why is the carbon cycle important?
- It regulates our climate, making it warm enough to survive.
What element does carbon exist in?
- gas, liquid and solid forms,
- in biotic / organic and abiotic/ inorganic forms.
- carbon moves between these forms (carbon pathway) through natural (biogeochemical) processes over time.
What does sequestering mean?
The natural storage of carbon by physical or biological processes such as photosynthesis.
How did the carbon cycle begin? (history of the carbon cycle)
- When primitive bacteria such as cyanobacteria started photosynthesising 3 billion years ago, they added oxygen to the atmosphere and absorbed CO2 from it.
- The higher oxygen levels allowed more complex organisms to develop about 2 billion years ago.
- CO2 was dissolved in the early oceans and then stored in sedimentary rocks, a process that accelerated when land based (terrestrial) ecosystems developed about 400 million years ago.
- The earth established its present carbon cycle balance about 290 mya, at the time of the carboniferous tropical rainforests.
- However, this balance has been altered since 1800 by human activities such as deforestation and burning of fossil fuels.
Why is the carbon cycle a closed system?
It does not have any external inputs or outputs.
Total amount of carbon is constant and finite
What does the carbon system include?
-stores: resevoirs/ pools/stocks where the carbon is held.
-fluxes: the movement or transfer of carbon between stores.
-processes: the physical mechanisms which drive the fluxes between stores.
What are the four carbon stores?
- the atmosphere gases such as CO2 and methane
-the hydrosphere (oceans, lakes etc) dissolves carbon dioxide
-the lithosphere: carbonates in limestone and fossil fuels.
-the biosphere: living and dead organisms
What is the geological carbon cycle (slow cycle)
A natural cycle that moves carbon between land, oceans and atmosphere. This movement involves a number of chemical reactions that create new stores which trap carbon for periods of time.
There tends to be a natural balance between carbon production and absorption in this cycle.
There can be occasional disruptions and short periods before the equilibrium is restored, such as when volcanos emit a lot of carbon
Describe the 6 stages of the geological cycle:
1) Terrestrial carbon held within the mantle is released into the atmosphere as CO2 when volcanoes erupt
2)CO2 within the atmosphere combines with rainfall to produce a weak acid (carbonic acid or acid rain) that dissolves carbon-rich rock, releasing hicarbonates. (chemical weathering)
3)Rivers transport weathered carbon and calcium sediments to the oceans, where they are deposited.
4)Carbon in organic matter from plants and from animal shells and skeletons sinks to the ocean bed when they die, building up strata of coal, chalk, limestone.
5)Carbon rich rocks are subducted along plate boundaries and eventually emerge again when volcanoes erupt.
6)The presence of intense heating along subduction plate boundaries alters sedimentary rocks by banking, creating metamorphic rocks. Co2 is released by the metamorphism of rocks rich in carbonates.
Fluxes used in the geological carbon cycle:
very fast:
1.photosynthesis
2. respiration
3.gases from volcanic eruptions
very slow:
4.sedimentary/ fossilation
What is the biogeochemical carbon cycle (fast cycle)
Determine how much of the carbon available on the Earth’s surface is stored or released at any one time.
The role of living organisms is critical in maintaining the efficient running of this system, because they control the overall balance between the store, release, transfer and absorption.
What are the five key processes of the biogeochemical carbon cycle (fast cycle)
-co2 is exchanged between atmosphere and oceans.
- photosynthesis- removing CO2 from the atmosphere to promote plant growth.
- respiration- releasing CO2 into the atmosphere as animals consume plant growth and breathe
- decomposition- breaking down organic matter and releasing CO2 into soils.
- combustion- burning fossil fuels- releasing CO2 and other greenhouse gases into the atmosphere.
How does the carbon cycle maintain an equilibrium?
- The impact of emissions from volcanic eruptions is to send extra Co2 to atmosphere, leading to rising temperatures, increasd evapo.
-This, leads to acid rain, which weathers rocks and created biocarbonates that will deposit on the ocean floor.
-This is slow, but this chemical weathering process rebalances the carbon cycle.
Explain the geological processes that influence the levels of carbon in the atmosphere (6 marks) - 2021
-The two geological processes that influence level of carbon in the atmosphere are chemical weathering and volcanic outgassing.
POINT 1- CHEMICAL WEATHERING
- Atmospheric carbon combines with precipitation to form a weak carbonic acid which reacts with rocks to form carbonates.
- Which are then carried by rivers to the oceans as well as sub-aerial processes at the coast causing carbonates to be deposited in the oceans.
- These marine organisms sequester carbon in shell building which eventually form sedimentary carbonate rocks.
- Subduction of the seafloor under the continental margins by tectonic spreading then causes some of this carbon to rise back up to the surface, then is “degassed” as CO2 goes back into the atmosphere.
POINT 2- VOLCANIC OUTGASSING
- Carbon is emitted into both the atmosphere and the ocean through a process known as “outgassing”.
- This is where CO2 that is contained in mantle fluids is released from the terrestrial stores.
- In subduction zones, subducted carbon sources, such as coal and shale are oxidated into co2 and vented back into the oceans or atmosphere.
-CO2 can also enter the atmosphere at continental rift zones. At divergent plate margins rising magma is enriched in co2 from deep mantle sources of carbon.
- CO2 is also vented at hotspots and non-erupting volcanoes where co2 passively diffuses into the atmosphere.
POINT 3- NEGATIVE FEEDBACK CYCLE
- Increase in volcanic activity
- rise in co2 emission and loss of carbon from rocks.
- temperature rises
- more uplift of air, condensation and rain.
- more chemical weathering and erosion of rocks.
- more ions deposited on ocean floors.
- more carbon stored in rocks.
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Explain how geological processes store carbon for a long time (8 marks)
Paragraph 1- limestone
- Limestone rocks contain a high concentration of calcium carbonate, which is formed partly from shell building organisms, such as corals, that extracted the mineral from seawater, and also from marine phytoplankton that absorb carbon through photosynthesis.
- Their remains accumulate on the ocean floor where over long periods of time they are cemented together and lithified into limestone.
Paragraph 2- Shale
- Biologically derived carbon in rocks like shale is formed when carbon from organisms is embedded in layers of mud.
- Over millions of years heat and pressure compress the mud and carbon, forming shale.
Paragraph 3- Fossil fuels
- Carbon fossil fuels (coal) were made up to 300 million years ago from the remains of dead organic material.
- Organisms once dead, sank to the bottom of rivers and seas, were covered in silt and mud, and then started to decay anaerobically.
- This process operates over millennia. When organic matter builds up faster than it can decay, layers of organic carbon become fossil fuels instead of shale.
