Earth's four spheres and the carbon that moves between them: photosynthesis, respiration, decomposition and burning fossil fuels. Concept tutorials with a landscape of the spheres and a live carbon cycle you can run for decades.
Earth's spheres and the processes that move carbon between them (AC9S9U03).
Earth can be described as four interacting spheres: the atmosphere (air), biosphere (living things), hydrosphere (water) and geosphere (rock, soil and magma). Many things sit where spheres meet.
Carbon is stored in every one of Earth's spheres: as carbon dioxide in the air, dissolved in the oceans, in living things and soil, and in fossil fuels and rocks. Carbon is never made or destroyed; it moves between these stores, and the carbon cycle is the map of those moves.
Photosynthesis moves carbon from the atmosphere into living things; respiration and decomposition move it back. These huge flows nearly balance, so the air's CO₂ stays steady until something upsets them.
Fossil fuels are carbon taken out of the cycle and stored in the geosphere over millions of years. Burning them returns it to the atmosphere in years, faster than plants and oceans can take it back, so CO₂ in the air rises.
A few quick questions on labelling the carbon cycle, which flows are natural and which are human, and how burning fuels changed the balance. Taught in class; use this to check yourself.
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