The Carbon Cycle Flashcards
What is the carbon cycle?
A closed system where carbon moves between stores (atmosphere, biosphere, hydrosphere, lithosphere) through processes like respiration, combustion, and sequestration.
What are the 4 major carbon stores?
• Lithosphere (rocks, fossil fuels) – 100,000 PgC
• Hydrosphere (oceans) – 38,000 PgC
• Biosphere (living organisms) – 2,000 PgC
• Atmosphere (CO₂ gas) – 750 PgC
What are carbon fluxes?
The movement of carbon between stores, e.g. photosynthesis, respiration, decomposition.
How does limestone form? (Give 5 steps)
1) Marine organisms with calcium carbonate (+ phytoplanktons) shells die
2) sink to the bottom of the ocean floor
3) more sediments fall on it
4) sediment reaches 100m in depth
5) compact under pressure and chemical reactions cause the formation into limestone.
How does coal form? (Give 3 steps)
1) coal is formed on land
2) Dead land-based plants settle in swamps
3) compact over millions of years to form peat and coal.
How does crude oil form? (Give 3 steps)
1) starts with the settling of fine-grained sediments and biologically degraded materials (needs to be 2% organic carbon)
2) Organic material in sediments undergoes anaerobic reactions which turns into liquid
3) due to its light density, crude oil may migrate upwards through layers of permeable or porous rock (But a layer of impermeable rock will result in the crude oil being trapped)
What is photosynthesis?
The process where green plants sequester CO2 through chloroplasts in their leaves to produce energy
How does respiration affect the carbon cycle?
Organisms release carbon dioxide into the atmosphere
How does decomposition affect the carbon cycle?
Decomposers break down organic matter, returning carbon to the soil or atmosphere.
How do phytoplankton contribute to the carbon cycle?
1) They absorb CO₂ from the atmosphere via photosynthesis,
2) as they sequester, they build their shells from calcium carbonate
3) this transforms the carbon in the atmosphere into biological carbon
4) some die and sink as some of these organisms are consumed by other organisms (e.g. zooplankton)
5) all of these consumer organisms will respire at some point which returns carbon to the atmosphere
What are greenhouse gases?
Gases that lead to the greenhouse effect
What are the 5 steps of natural greenhouse effect?
1) Solar radiation enters the earth’s atmosphere by passing through the GHG layer
2) this radiation is mostly absorbed by the earth’s surface whilst some is reflected
3) some of this reflected radiation will pass back into space
4) the GHG layer acts as a blanket, which stops the majority of this reflected radiation leaving the earth’s radiation
5) this allows the earth to be at a high enough temperature to support life
How much do these sequester carbon per year? (Marine phytoplanktons, terrestrial primary producers, tropical rainforests)
Marine phytoplanktons = 5 - 15Gt
terrestrial primary producers = 100 - 120Gt
tropical rainforests = 2200g/m^2
What are the 3 impacts of the greenhouse effect?
1) temperature distribution
2) Albedo effect
3) precipitation distribution
What is the natural greenhouse effect?
Greenhouse gases (CO₂, CH₄) trap heat, keeping Earth warm enough to support life.
What is the enhanced greenhouse effect?
When human activities (burning fossil fuels, deforestation) increase greenhouse gas levels, trapping more heat and raising global temperatures.
What is the albedo effect?
Where Light surfaces (ice, snow) reflect sunlight, while dark surfaces (oceans, forests) absorb heat, affecting temperature distribution.
How do wildfires influence the carbon cycle? (3 things)
• Burn vegetation, releasing stored CO₂
• Reduce forest carbon sinks
• Can promote regrowth, restoring sequestration
What are fossil fuels?
The term given to oil, coal and natural gas
What is arctic amplification?
When the arctic is warming at twice the rate
What is methane (CH4)?
A natural gas that is created as a by-product in formation of coal and crude oil
What is chemical weathering?
chemical weathering is the wearing away of rock by chemical reactions (causing material to dissolve through solution, hydrolysis and oxidation)
How does chemical weathering of rocks happen? (Give 3 steps)
1) slightly acidic rain forms from CO2 in the atmosphere being dissolved into rain water
2) when acidic rain hits carbon-rich rocks, it can dissolve material and form calcium carbonate
3) these dissolved materials are then transported down rivers and deposited into seas
How does volcanic out-gassing occur?
1) extreme heat leads to sedimentary rock undergoing chemical changes
2) causes CO2 to be released in the atmosphere
