Rivers are fresh, but oceans are salty. Why?
If you have ever tasted sea water, you know it is super salty! But rain water is fresh, and river water is fresh. So where does the salt come from?
Believe it or not, the salt comes from land. When it rains, the water washes over rocks and dissolves tiny amounts of minerals and salts. This salty water flows into rivers, and rivers carry it to the ocean.
When the sun shines on the ocean, water evaporates (turns into clouds) to make rain again. But the salt stays behind! Over millions of years, this salt has built up.