Soil-Forming Processes

Part of the overall hydrologic cycle of the Earth involves the interaction of water with the land. This interaction involves weathering and erosion which contribute to the formation of soil. Seeming so ordinary, the soil is vital to life on the planet. Lutgens and Tarbuck quote the description "the bridge between life and the inanimate world." Reaching more toward the poetic, they quote Jack Eddy who describes "the Earth as a planet ... where a thin blanket of air, a thinner film of water, and the thinnest veneer of soil combine to support a web of life of wondrous diversity and continuous change."

More prosaically, they describe soil as a combination of mineral and organic matter, water, and air that supports the growth of plants. About half the volume of good quality soil "is a mixture of disintegrated and decomposed rock (mineral matter) and humus (the decayed remains of plant and animal life)." That leaves half the volume for spaces where air and water circulate.