Soil is the solid material on Earth’s surface that results from the interaction of weather and biological activities with the underlying geologic formation. Soil is produced from broken down rocks, organic matter (decayed animal and plant life), water, and air. Soil generally loosens from its parent material at a rate of one centimeter every 250 to 2,500 years. This lesson encourages students to think about the differences in soil. The Table of Contents, Preface, and a section that describes how to use this book are included in this free selection.