A detailed and in-depth PowerPoint covering the entirety of the carbon cycle and energy security topic in A-level geography made specifically for the Edexcel exam board. Includes easy-to-read and condensed notes with case study examples to use. Made by a 2023 A* Geography student.
Carbon Cycle and Energy
Security
Whole A-level topic content including case studies, definitions and in
depth explanations made for Edexcel specification
,Enquiry question 1
,6.1 Geological cycle (long-term)
Carbon exists in gas, liquid, solid, biotic and abiotic forms. It moves between these forms (carbon pathway) through natural biogeochemical process
timescale
Main carbon stores:
6.1a Carbon stores - Marine sediments and sedimentary rocks – lithosphere = biggest
- Small carbon stores – organic part of marine ecosystem (3PgC) 100,000 billion metric tons)
- Large carbon stores – oceans (deep ocean = 37,100PgC), terrestrial ecosystems (550PgC), - Oceans – hydrosphere (38,000 billion metric tons) – carbon consta
sedimentary rock (83,00,000PgC), atmosphere store (589PgC) utilised by marine organisms, lost as output to the lithosphere or g
The stores are sometimes referred to as ‘sinks’. There is an exchange of carbon between these input from rivers and erosion
stores over a yearly timescale called annual fluxes. - Fossil fuel deposits – lithosphere – humans have developed techn
exploit them rapidly
6.2b Where carbon is found - Soil organic matter – lithosphere – deforestation, agriculture and l
- Most of the earth's carbon is geological, sedimentary carbonated rocks (such as change are affecting this store
Limestone) that contain a high concentration of calcium carbonate due to being - Atmosphere – dynamic – human activity has caused CO2 levels in
formed from shells/skeletons of marine creatures (coral) that extract carbon from atmosphere to increase by around 40% since the industrial revolut
seawater, and also from phytoplankton which absorbs carbon through photosynthesis - Terrestrial plants – biosphere – vulnerable to climate change and d
- Limestone is also formed from the direct precipitation of calcium carbonate from salt and as a result carbon storage in forests is declining annually
or freshwater or the evaporation of seawater. (Limestone vulnerable to chemical
weathering – rain becomes weak carbonic acid + dissolves calcium carbonate =
transfer of dissolved carbon to the seabed)
- Coal – anaerobic reactions can convert 90% of organic carbon into crude oil (contains
85% carbon) – moves into permeable/porous rick where trapped within impermeable
rock
6.2c carbon release
- chemical weathering – of carbon-rich rocks such as limestone – rainwater absorbs CO2 from the atmosphere = carbonic acid, dissolved rock minerals to form new mine
carbonate)
- Rivers carry these minerals to sea = deposited + new rock formed
- Tectonic forces may bring carbon-rich sedimentary rock into contact with extreme heat = chemical changes and the release of CO2 into the atmosphere
- Subduction zone = constructive pate boundaries or intra-plate locations = release of CO2. carbon also recycled with carbonate rocks dragged into the mantle
- Outgassing from the main vent of the volcano, hotspots or constructive plate boundaries e.g. Yellowstone
Volcanic activity releases around 300million tonnes of
, Fluxes of the carbon cycle
Biological and chemical processes determine how much carbon is stored and released:
- Photosynthesis – by removing CO2 from the atmosphere, plants are sequestering carbon and reducing the potential impacts of climate change
chlorophyll o the leaves reacts with CO2 to create carbohydrate glucose.
- Respiration – converts oxygen and glucose into energy then produces waste products of water and CO2.
o During the day plants photosynthesis (absorb more CO2 than they emit from respiration) but at night they don’t photosynthesise but do
more CO2 than they absorb). Overall they absorb more CO2 than they emit = they are net carbon dioxide absorbers and net oxygen prod
- Combustion – when fossil fuels and organic matter are burnt they emit CO2 into the atmosphere
- Decomposition – when living organisms die they’re broken down by decomposers (bacteria, detritivores) which respire, returning CO2 into the
organic matter is also returned to the soil
- Diffusion – oceans absorb CO2 from the atmosphere (increased ocean acidity by 30% since pre-industrial times which is harming aquatic life – c
- sedimentation – when shelled marine organisms die and shell fragments fall to ocean floor, compact over time to form limestone = fossil fuel de
- Weathering and erosion – inorganic carbon released slowly through weathering (when rocks eroded by carbonation (carbonic acid)). Marine or
carbon to build up their shells
- Metamorphosis – formation of metamorphic rock some carbon is released and some is trapped
- Volcanic outgassing
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