Why is Sea Water Salt?

-N. CHOKKAN

You all know that seas receive fresh water from many rivers. But…then, why is the sea water salty and river water not so? Where do seas get the taste from? 

To understand this, let’s listen to a small story.

Once upon a time there was an old man in a village. He was the local banker. So the merchants of the village would deposit their earnings with him as they knew the old man would keep their money safe and they could take it back whenever they needed it. These merchants used to bring money in yellow envelopes. The old man would open the envelopes, take out the money and keep it safe and throw away the envelopes in one corner of his house. After many years, his househad thousands of yellow envelopes. How? 

The old man accumulated yellow envelopes while collecting money from the merchants. But when he gave the money back to them, the merchants did not take back their yellow envelopes along with the money. So all the yellow envelopes had settled with the old man. The same story is happening with rivers and seas. 

Rivers are the ‘merchants’ that bring water to the sea. Rivers, on their way to the sea, go through soil and rocks. When rivers move over rocks, they dissolve a little of the rock thereby carrying the salt. They then carry this salt to the sea. So, the river water is actually salty but the salt content is very low that you wouldn’t feel the salty taste. 

When water evaporates from seas into the atmosphere to fall again over land as rain or snow and forms as rivers and lakes, the salts that seas contain are left behind.

As a result, like the old man who had been left with a large supply of yellow envelopes, seas are left with a large supply of salt. This process makes sea water salty. 

Another factor that provides salts to seas is the eruption of volcanoes under water, resulting in seawater reacting with hot rock and dissolving the mineral constituents. As new minerals are forming on sea floor at the same rate as salt is added to seas by water bodies, the salt content of seawater does not change and is at steadystate.