Johnnie M. Tolbert, Age 15, Of Brewton, Ala.,, for his question:     

How did the earth become covered with soil?     

Soil is a mixture of crumbled minerals and organic material. Plants use its organic chemicals to grow and support animals. As they rot and decay, plants and animals return more organic materials to the soil. The minerals in the soil come from rocks that are broken apart by weathering and water. It takes 100 years of –this slow process to form one inch of good soil. Perhaps the first soil came from shallow pools teeming with algae and marine animals. The waters dried up, leaving a silty mixture of minerals and decaying materials. Other 1ayers of soil were started by bacteria, lichen, insects and other small creatures living at the fringes of the ancient seas.