Sulphur is one of important of proteins vitamins and hormones. It plays a very crucial role in health of both plants and animals. Most of earth sulphur is tied up in rocks and salts or buried deep in ocean sediments. 

The main steps of sulphur Cycle:

1.        Sulphur enters into atmosphere in the form of H₂S, SO₂  by both  natural and human activity. Natural activity:  volcanic eruptions, hot springs, decay of dead organisms etc.

Human activity:  industrial, automobile, emissions.

2.       In atmosphere SO₂ either reacts with O₂ and forms sulphur trioxide (SO₃) gas or with other chemicals and forms sulphur salts. SO₃ finally dissolve in water to produce sulphuric acid (H₂SO₄).

3.      Sulphur in the H₂SO₄ finally comes down on earth with fog and rainfall. Here it is absorbed by plants in the form of sulphates and utilize in protein synthesis.

4.      Animal eat plants and hence sulphur is passed on to animals. Excess of sulphur is excreted out as faecal matter.

5.      When animal dies the bacteria decompose it, in anaerobic condition H₂S gas is formed and in aerobic conditions SO^2-₄   IS formed which is used by plants from soil.

6.      Sulphur enters the oceans through from earth's atmosphere.

Within the oceans, some sulphur cycles through marine communities, moving through the food chain. A portion of this sulphur is emitted back into the atmosphere from sea spray. The remaining is locked to the depth.