Question: Why is there salt in the sea.

Samantha Weaver answered on 4 Jul 2012:

Sea water has been defined as a weak solution of almost everything. Ocean water is indeed a complex solution of mineral salts and of decayed biologic matter that results from the teeming life in the seas. Most of the ocean’s salts were derived from gradual processes such the breaking up of the cooled igneous rocks of the Earth’s crust by weathering and erosion, the wearing down of mountains, and the dissolving action of rains and streams which transported their mineral washings to the sea. Some of the ocean’s salts have been dissolved from rocks and sediments below its floor. Other sources of salts include the solid and gaseous materials that escaped from the Earth’s crust through volcanic vents or that originated in the atmosphere. At least 72 chemical elements have been identified in sea water, most in extremely small amounts. Probably all the Earth’s naturally occurring elements exist in the sea.

The salinity (saltiness) of sea water varies. It is affected by such factors as melting of ice, inflow of river water, evaporation, rain, snowfall, wind, wave motion, and ocean currents that cause horizontal and vertical mixing of the saltwater. The saltiest water occurs in the Red Sea and the Persian Gulf, where rates of evaporation are very high. Of the major oceans, the North Atlantic is the saltiest. Low salinities occur in polar seas where the salt water is diluted by melting ice and continued precipitation.