Layers Of Soil

  • Soil

 Soil is composed of layers of rock material, minerals and organic matter - a combination capable of supporting the growth of root plants, soil scientists classify soils into 12 different orders, distinguished by physical, chemical, and biological characteristics. within each order, there are many soil types. In the united states alone, there are more than 20,000 different types.
   The slow, continuous physical and chemical breakdown of rocks and minerals begins the process of making soil, along with the decomposition of organic matter and incorporation of water and air.
   The type of parent rock affects the overall chemical composition and texture of the soil. for example, limestone creates soil rich in calcium, while shale develops a smooth, clayey soil is formed depends on the environment. Less than an inch of soil may form annually in the humid tropics.

  • Layers Of Soil

Soil Layers, also called horizons, differ in composition and depth and are defined according to location. The soil profile shown here represents a clayey soil common in parts of the southeastern United States.
Lairs Of Soil
1. HORIZON O Up to 1 inch thick. Decomposing material such as leaf litter and humus, on its way to becoming topsoil.

2. HORIZON A 6-8 inch thick. The dark topsoil contains organic material and animals ranging from microscopic bacteria to worms and burrowing shrews.

3. HORIZON E A few inches thick. Lighter in colour than HORIZON A as a result of minerals leaching downward.

4. HORIZON B 1.5-2 feet thick. High iron content turns this layer red. Also called subsoil.

5. HORIZON C Soil is born here, where water and temperature join to break bedrock, Volcanic ash, or sediment down into smaller particles. Little Organic material found here.

6. HORIZON R (not seen in the illustration) solid bedrock, unweathered, beneath the layers.

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