We can discuss the movement of carbon around the
Earth by describing a carbon cycle. This is
because the total amount of carbon on the Earth
doesn't change -- what changes is where the carbon
resides.
This figure is from
Daniel
Jacob's excellent book "Introduction to Atmospheric
Chemistry." The units for the reservoirs are
Pg C and the fluxes are in Pg C per year. A Petagram is
10^15 grams.
Note how carbon makes its way back into the biosphere.
What name would you give to that process?
What is the biggest reservoir of carbon on the Earth?