Dick Hensel, age 12, of Racine, Wis., for his question:

What is loess?

Much of the rich soil of the Mississippi basin is loess. The word loess is coined from an older word meaning to pour or loosen. This loose mixture of earthy debris seems to have been poured over vast surfaces of the earth. It supports large farmland areas in north and. central Europe, eastern China and in Russia.

Loess soil is usually rich in minerals, especially calciums. With plenty of water, it can provide the minerals needed. by crops and other plants. It is also often rich in fossils. Tiny sea shells turn up, often far from the sea, and a plow cutting through loess soil may reveal the fossilized bones and teeth of bygone mammals.