Phosphorus cycle

Phosphorus cycle, FOS fuhr uhs, is the circulation of phosphorus among the rocks, soil, water, and plants and animals of the earth. Human beings and all other organisms must have phosphorus to live. In nature, most phosphorus occurs in phosphate rock, which contains phosphate ions combined with calcium, magnesium, chlorine, and fluorine. Phosphate rock forms as sediments at the bottom of the oceans. Some of these sediments are eventually returned to land by movements of the earth's crust. More »