Why Is Seawater Salty?

When rain water flows through the earth’s surface, it dissolves a minute amount of minerals, such as salt. These dissolved minerals eventually reach the sea via rivers and streams that empty into it.

The sea water evaporates and cycles back as fresh water (rain), but the dumped minerals in the sea have nowhere to go. Slowly, over hundreds of millions of years, the sea water has become salty.

Another source that makes the sea water salty is underwater volcanic activity.  In these underwater volcanoes, water gets heated by the rocks of the oceanic crust. The heat and the water dissolve small amounts of minerals and adds to the amount of salt in the ocean.

According to scientists (take it with a pinch of salt, no pun intended), the salt level in the seas has not changed for several hundred million years.