Why is the Ocean salty?

Every now and then, we come across a fact about our earth which mystifies us and for which no answer has yet been found. Such a fact is the existence of salt in the oceans. How did it get there?

The answer is we simply don't know how the salt got into the ocean! We do know, of course, that salt is water-soluble, and so passes into the oceans with rain water. The salt of the earth's surface s constantly being dissolved and is passing into the ocean.

But we don't know whether this can account for the huge quantity of salt that is found in oceans. If all the oceans were dried up, enough salt would be left to build a wall 180 miles high and a mile thick. Such a wall would reach once around the world at the Equator! Or put another way, the rock salt obtained if all the oceans dried up would have a bulk about 15 times as much as the entire continent of Europe!

The common salt which we all use is produced from the sea water or the water of salt lakes, from salt springs, and from deposits of rock salt. The concentration of salt in sea water ranges from about three per cent to three-and-one-half per cent. Enclosed seas, such as the Mediterranean and the Red Sea, contain more salt in the water than open seas. The Dead Sea, which covers an area of about 340 square miles, contains about 10,523,000,000 tonnes of salt.

On the average, a litre of sea water contains approximately 30 grams of salt. The bed rock salt that are formed in various parts of the world were all originally formed by the evaporation of sea water millions of years ago. Since it is necessary for about nine-tenths of the volume of sea water to evaporate for rock salt to be formed, it is believed that the thick rock salt beds that are found were deposited in what used to be partly enclosed seas. These evaporated faster than fresh water entered them, and the rock salt deposits were thus formed.

Most commercial salt is obtained from raock salt. The usual method is to drill wells down to the salt beds. Pure water is pumped down through a pipe. The water dissolves the salt and it is forced through another pipe up to the surface.