The Carbon Cycle Flashcards
Which (debatably) are the most important elements for life
‘CHOP’
Carbon, hydrogen, oxygen and phosphorus
How could you say CO₂ and O₂ is cycled between aerobically respiring organisms and primary producers
Plants produce O₂ in photosynethesis
Animals and plants utilsise O₂ in respiration and produce CO₂ as a byproduct
How does photosynthesis work
Light will promote electrons with chlorophyll and CO₂ reacts with RuBP, and through a series of reaction large complex organic sugars are formed
Water is then used to remove any electrons
These sugars are then stored and used by the plant
How does aerobic respiration work?
breaks down large organic sugars using oxygen forming ATP
ATP is then hydrolysed to release energy
What is the difference between organic and inorganic carbon
Organic carbon has been reduced (gain of electrons) e.g. organic sugars
Inorganic carbon has been oxidised (loss of electrons) e.g. CO₂, H₂CO₃
HCO₃
Photosythesis is considered the reduction of carbon (CO₂ to complex sugars)
Aerobic respiration is considered oxidation of carbon (complex sugars to CO₂)
How would the presence of lots of reduced carbon in the world, related to its oxidation state
Low levels of oxygen, as the large organic carbon molecules have not been oxidised, and hence remain in the reduced form
What is Oxidation
The loss of electron OR and increase in oxidation number
What is Reduction
Is the gain of electrons OR a decrease in the oxidation number
What is a redox reaction
A reaction where one species is oxidised and one species is reduced
If a substance has a highly positive redox potential
It is likely to gain electron (be reduced)
If a substance has a highly negative redix potential
it is likely to losses electron (oxidised)
Name a way dead organic matter can be broken down
Fungi and microbes will consume organic matter in the form of decay
What is the shortest Organic Carbon cycles
- On land, production of reduced organic carbon by photosynthesis is balanced by the production of oxidised carbon by respiration and decay
(plants however need to be consumed for this repsiration to occur
It is a never ending cycle) - Photosynthesis is also balance by decay as the of the tree will return any carbon back to the atmosphere in the form of photosynthesis
The short-term carbon cycles occurs around every 1000yrs
What does it involve
Microscopic microplankton will photosynthesis (short life span where they will quickly die) and life the ocean floor, where it decays back to CO₂
The deep oceans becomes enriched in CO₂
But carbon is recyled to the surface every 1000yrs, when water is slowly moved from the N.Atlantic to the Pacific ocean and brought up to the surface
dead microscopic microplankton line the ocean floor when they have died and broken down into CO₂ during decay
Why would this not happen
Small amounrs of organic carbon will become buried in ocean sediments which will become rock, becoming part of the fossil record
Hence they don’t move to the Pacific as they become part of ocean sediment like rock
Describe the long-term carbon cycle (across around 300 million years)
This reduced carbon does not decay and instead returns its carbon and oxygen to the atmosphere quickly
Over millions of years, it has accumulated into a vast reservoir of reduced carbon (including coal, oil and gas)
However, the reduced carbon in rocks is turned back to CO₂ by exposure to atmospheric oxygen
In the long term carbon cycle there are 4 ways CO₂ can be returned to the atmosphere, name them:
- Subducted Calcium carbonate and Organic carbon forms mantle and the is put back into the atmosphere by volcanoes
- Coal, oil and gas is converted back to CO₂ when it comes into contact with oxygen at the surface
- Release of CO₂ from sedimentary organic C weathering
- Release of CO₂ and CH₄ from metamorphism and deep diagenesis
In the long term carbon cycle there are 4 ways carbon can enter this system, name them:
- Subduction of calcium carbonate and organic carbon
- conversion of CO₂ to dissolved HCO₃⁻ by Ca-Mg silicate weathering
- Burial of calcium carbonate into oceans
- Burial of Organic carbon into oceans
What is metamorphism
is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. It takes place at high temperatures temperatures (excess of 150 to 200°C) and pressures
What is silicate weathering
CaSiO₃ + CO₂ → CaCO₃ + SiO₂
Silicate weathering of rocks uses gaseous CO₂
The byproducts are the transported into rivers and oceans where they are stored
The calcium carbonate is used by organisms to build shells etc
In the Long-term carbon cycle, describe to feedback loop between weathering and volcanism
Weathering - removes CO₂ from the atmosphere
Volcanoes - returns CO₂ to the atmosphere
How can the weathering and volcano feedback loop also affect the stability of our climate
- If CO₂ levels are higher - temperature will increase - leading to faster silicate weathering - leading to more CO₂ to be removed from the atmosphere
- If CO₂ levels are lower - temperature will decrease - leading to slower silicate weathering - leading to less CO₂ to be removed from the atmosphere
The Earth’s temperature is stabilised by opposing CO₂ inputs from volcanic activity and CO₂ removal by silicate weathering
Why does this guarantee absolute stability
- Volcanic acitivity varies
- Greenhouse gases can be added in other ways (anthropogenic impacts)
- Silicate weathering rate varies
- Carbon bural rate varies
For most of the time the Earth has been warmer than it is today (there has been temperature decline for the past 60MYA)
Has this been caused by less CO₂ in or out
The level of volcanic eruption has not changed
Therefore it must be to do with more silicate weathering - hence more CO₂ being removed from the atmosphere
It is suspected due to the increase in mountainous terrian which will experience high levels of weathering (in particular the Andes and Himalayans)
There have also been increase Monsoons, leading to higher rainfall and weathering
Why are the Himalayans and Andes said to be responsible for this increases weathering
Around 50MYA there was a super continent which included the US, New Zealand, India and Australia
India started rapidly moving North, where it eventually collided with Asia
This contiental collision created mountain belts and the Himalayans being pushed up - this is thought to have affected weathering and hence the current climate
Why are volcanoes so important
if all the volanoes ceased to be active you would not have any replenishment of CO₂
All atmospheric and oceanic CO₂ would be removed in 1MY
