Why are the oceans salty? What keeps the ocean at the same level of saltiness?

Most of the salt in the ocean is there because of the processes of dissolving and leaching from the solid earth over hundreds of millions of years, according to Dr Eugene C LaFond, President of LaFond Oceanic Consultants. Rivers take the salt out of rocks and carry them into oceans;these eroded rocks supply the largest portion of salt in the ocean.

But other natural phenomena contribute to the mineral load in the oceans. Salty volcanic rock washes into them. Volcano also release salty 'juvenile water', water that has never existed before in the form of liquid. Fresh basalt flows up from a giant rift that runs through all the ocean' basins.

With all of these processes dumping salt into the oceans, one might think that the sea would get saturated with sodium chloride, for oceans, like any other body of water, keep evaporating. Yet, according to the Sea Secret Information Services of the International Oceanographic Foundation at the University of Miami, the concentration of salts in the ocean has not changed for quit a while - about 1.5 billion years. So how do oceans rid themselves of some of the salt?

First of all, sodium chloride is extremely soluble, so it doesn't get concentrated in certain sections of the ocean. The surface area of the oceans is so large that the salt is relatively evenly distributed. Second, some of the ions in the salt leave with the sea spray. Third, some of the salt sticks to particulate matter that sinks below the surface of the ocean. The fourth and and most dramatic way sodium chloride is removed from the ocean is by the large accumulations left in the salt flats on oceans coast, where the water is shallow enough to evaporate.

Thus the level of salt in the ocean, approximately 3.5 per cent, remains constant.