Why Is the Sea Salty?

Answer:

The water in the sea is a salty brew. The amount differs from place to place, but on the average about 3.5 percent of seawater is dissolved mineral salts. The commonest by far is sodium chloride, ordinary table salt.

Some of the salts were contributed by submarine volcanoes, but most originated in the rocks of the earth’s crust. As the rocks were disintegrated by weathering, the salts were released, and rivers carried them to the sea. As the seawater evaporated in the never-ending water cycle, the salts were left behind and gradually accumulated to their present concentrations. In all, the oceans contain enough salt to form a layer some 500 feet thick over all the dry land on earth.