The four biogeochemical cycles include the water cycle, the carbon cycle, the phosphorous cycle and the nitrogen cycle. These four cycles involve biology, chemistry and geology and describe the flow of nutrients and waste products on Earth.
The water, or hydrologic, cycle, primarily involves the evaporation of moisture from the ocean and its return to lakes, oceans, waterways and groundwater sources in the form of rain. The carbon and phosphorous cycles primarily involve the flow of nutrients and biological wastes to and from plant, animal and microbiological life. The nitrogen cycle is more complex, as nitrogen is fixated by lightning, ultraviolet radiation and bacteria in some processes and returned to Earth's atmosphere in other processes.