Kathy Hickman, age 8, of Oak Hill, West Virginia, for her question:

What makes the sea so salty?

The salt in the sea is a mixture of chemicals. They are dissolved fn tiny particles that are too small for our eyes to see. These salty chemicals once belonged to the land. They were mixed with the rocky minerals. When water runs over stones or sinks underground, it dissolves some of the salty chemicals. If you stir a pinch of salt into a glass of water, you can watch it dissolve and disappear.

This is what happens in a big way when streams and rivers run along over the earth. This water dissolves salts and all sorts of other chemicals from the land. And sooner or later, the streams empty into the seas. The sun evaporates moisture from the ocean, but the salty chemicals stay behind. This has been going; on for billions of years. Every day, the streams dump more dissolved chemicals and the seas get a little bit saltier.