Soil Formation and Classification

substances down into the E layer or eluviation horizon. This lighter layer is very mineral-rich as a result of leaching.

The B horizon is the subsoil. This is where you have humus and sediment that is removed from the upper soil layers and where chemical weathering is taking place. The upper part of the zone is called regolith, which is porous and has highly-weathered sediment. The Saprolite area or lower zone, where there is parent rock and little organic material.

Below these is the C horizon, which is the substratum. Mechanical weathering happens here as bedrock gets broken but not very altered in a chemical way. No organic material exists here. The R horizon is the bedrock. The parent bedrock and some rock fragments live here in the absence of weathering.

There are different taxonomic classifications for the various known soil types. There is a difference between volcanic soils and prairie soils. The dust storms of the 1930s in the American Southwest happened because there were too many people trying to develop the prairies without understanding the problems in doing this. They planted crops with shallow roots, replacing prairie plants with deep roots.

SOIL FORMATION AND CLASSIFICATION

Soils are given a name that usually comes from where they were first mapped. Soil surveys will be done to determine what kind of soil exists in any given area. This leads to soil taxonomy that uses a soil's color, structure, texture, and related properties.

There are several factors that go into making soil. You need to consider a number of variables going into any given soil, including these:

• The parent material. Most soils form in materials coming from elsewhere. Some comes from wind that has blown into an area. Glacial till makes soil that has been moved by a glacier. The material where the soil came from is called the parent material. Some deeper material remains unchanged after it was originally deposited. The texture of sediment in streams depends on how fast the stream is moving.