Why is the ocean salty?

1the puzzle

Rivers pour into the ocean every single day. So why isn't the ocean fresh water, like the rivers feeding it?

2rain dissolves rock

Rain falling on land is slightly acidic. As it trickles over rock, it dissolves tiny bits of minerals — including salts — out of the stone.

3rivers carry it

Rivers carry those dissolved salts, drop by drop, all the way down to the sea. Every river on Earth is quietly delivering a little salt.

4water leaves, salt stays

Now the key trick: the sun evaporates ocean water into clouds — but only the pure water leaves. The salt stays behind, every time.

5billions of years

That cycle has run for hundreds of millions of years. No salt ever leaves the sea, so it just keeps building up — that's why it's salty.