Let me draw you a picture...: Why is the sea salty?

Most of you have at one point or another gone to the seaside, chased around jellyfish, filled all crevices with sand, and maybe gotten a nasty sunburn. Through your merry beach adventures, you’ve no doubt discovered, or confirmed, the simple fact that seawater is salty.

And that may seem normal, it’s such a common knowledge we don’t really question it at first. But if we think about it, rain, rivers, and even ice caps are all made out of fresh water, yet they flow in or rest onto the sea. So why is it salty?

A long, long time ago when the earth was still young and hot, volcanoes continuously pumped noxious gases into the atmosphere. Along with the greenhouse gases and heavy particles, water vapour floated in the air. So when the planet cooled and the first clouds formed century long rains brought everything down into the lowlands. Gases dissolved, particles fell, and the new oceans obtained their particular flavour.

But back then, they were not as salty as they are today.

Through the years, as all those rains fell, and all the rivers carried water down the rocky slopes, minerals gradually eroded and washed down, accumulating into the oceans. The largest source of the salt we find in the seas today is this kind of erosion.

(One of these minerals is gold. We actually find more in the ocean than there is on land, but extracting it is so expensive, it’s far more profitable to leave it alone.)

Additionally, underwater volcanoes keep spitting gases and minerals into the oceans even today.

And finally, water constantly escapes the seas through evaporation, leaving behind the heavier particles, and returning to the land to wash away even more salts. A process known as the water cycle.

So as ages pass, salt and other elements pile up, making the seas more and more salty. The salt concentration is not equal throughout. The poles are fresher because of continuous melting, and the equator is saltier, due to constant evaporation.

But to us it always tastes the same, like salty water.