June Lindem, age 13, of Rockford, Ill., For her questiont

How long does it take to make an inch of topsoil?

The making of topsoil is a long and patient process. The basic ingredient is powdered minerals, crumbled from the solid and durable rocks by countless ages of weathering. Organic materials are added by the bodies and waste materials of insects and other animals, by fallen leaves and by rotted plants. The powdered rock is not soil without these and other organic remains from once living plants and animals.

Some soil forms faster than others. But experts estimate that it takes about 100 years to form a layer of topsoil 1 inch deep. This soil feeds the plants that supply our food, and every farmcr knows its value. We try to save and conserve it, but an untamed flood can wash away layers of topsoil that took many hundreds of years to form.