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 rainwater. The salt of the earth’s surface is 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 seawater or the water of salt lakes, from salt springs, and from deposits of rock salt.
The concentration of salt in seawater ranges from about 3% – 3,5%. 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 11.600.000.000 tons of salt!
On average, a gallon of seawater contains about a quarter of a pound of salt. The beds of rock salt that are formed in various parts of the world were all originally formed by the evaporation of seawater millions of years ago.
Since it is necessary for about 9/10 of the volume of seawater 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 freshwater entered them, and the rock-salt deposits were thus formed.
Most commercial salt is obtained from rock 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.
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