The phosphorus cycle includes the following steps:
Phosphorus in fertilizer, rocks, and mountains is distributed by rain to nearby land and bodies of water
Animals eat the plants grown by fertilizer. They expel the phosphorus as waste. It eventually reaches the water as runoff.
Phosphorus is cycled through animals that live in water. It is eventually deposited into the ocean floor.
Phosphates contribute to the sediment at the bottom of the water. That sediment becomes rock
The ocean bed eventually becomes a mountain range over several millions of years because of normal geological functions
The phosphorus in those mountain ranges is washed off into bodies of water and the cycle begins again and again.
Diagram
The Phosphorus cycle
References
Friedland, Andrew J., Rick Relyea, and David Courard-Hauri. "The Phosphorus Cycle." Environmental Science for AP*. New York: W.H. Freeman, 2012. N. pag. Print.