Terrestrial carbon stores Flashcards
What is the carbon cycle?
The carbon cycle is the cycle by which carbon moves from one Earth sphere (atmosphere, hydrosphere, lithosphere and biosphere) to another.
It is a closed system but is made up of interlinked subsystems which are open and have inputs and outputs.
How does carbon exist in the atmosphere?
As carbon dioxide (CO2) and carbon compounds, such as methane (CH4)
How does carbon exist in the hydrosphere?
As dissolved CO2
How does carbon exist in the lithosphere?
As carbonates in limestone, chalk and fossil fuels, as pure carbon in graphite and diamonds.
How does carbon exist in the biosphere?
As carbon atoms in living and dead organisms.
How do the carbon stores vary?
Size, capacity and location
What is the important distinction in the biosphere in terms of carbon stores?
Terrestrial and oceanic locations
How are carbon fluxes between the carbon stores of the carbon cycle measured in?
Either pentagrams or gigatonnes of carbon per year.
What are the major fluxes of carbon?
Between the oceans and the atmosphere, and between the land and the atmosphere via the biological processes of photosynthesis and respiration.
Fluxes may vary in what two things?
Rates of flow
Timescales
Most of the Earth’s carbon is geological and results from what?
The formation of sedimentary carbonate rocks (limestone) in the oceans.
Carbon derived from plants and animals in shale, coal and other rocks.
Explain the formation of sedimentary carbonate rocks (limestone) in the oceans.
The Himalayas form one of the Earth’s largest carbon stores.
This is because the mountains started life as ocean sediments rich in calcium carbonate derived from crustaceans, corals and plankton.
Since these sediments have been upfolded, the carbon they contained has been weathered, eroded and transported back to the oceans.
Explain the carbon derived from plants and animals in shale, coal and other rocks
These rocks were made up to 300 million years ago from the remains of organisms. These remains sank to the bottom of rivers, lakes and seas and were subsequently covered by silt and mud.
As a consequence, the remains continued to decay anaerobically and were compressed by further accumulations of dead organisms and sediment.
The subsequent burning of these fossil fuels has released large amounts of carbon they contained back to the atmosphere.
The release of geological carbon into the atmosphere results not just from people burning fossil fuels, but also through which two natural processes?
- Carbon dioxide in the atmosphere reacts with moisture to form weak carbonic acid. When this falls as rain, it reacts with some of the surface minerals and slowly dissolves them, i.e. there is chemical weathering.
- Pockets of carbon dioxide exist in the Earth’s crust. Volcanic eruptions and earthquakes can release these gas pockets. This outgassing occurs mainly along midocean ridges, subduction zones and at magma hotspots.
What is outgassing?
Outgassing is the release of gas previously dissolved, trapped, frozen or absorbed in some material.
