Soil Profile

Soil Profile

Soil is composed of distinct layers. Perform the following activity to find out how these layers are arranged. A vertical section through different layers of the soil is called the soil profile. Each layer differs in feel (texture), and known as horizon.

A Horizon-

This layer is the top15cm of the soil profile and has the highest percentage of organic matter. The layer was likely formed from decomposing plant and mineral materials. It has a large amount of sand, likely deposited from the floods of Walnut Creek

B Horizon-

The B horizon is commonly referred to as the "subsoil". In humid regions, B horizons are the layers of maximum accumulation of materials such as silicate clays, iron (Fe) and aluminum (Al) oxides, and organic material. These materials typically accumulate through a process termed illuviation, wherein the materials gradually wash in from the overlying horizons. Accordingly, this layer is also referred to as the "illuviated" horizon or the "zone of accumulation". In addition, it is defined as having a distinctly different structure or consistency than the horizon(s) above and the horizon(s) below. The B horizon may also have stronger colors (higher chroma) than the A horizon. In arid and semiarid regions, calcium carbonate or calcium sulfate may accumulate in the B horizon.

C Horizon-

The C horizon (parent rock) is below the B Horizon. This layer is little affected by soil-forming processes and they thus have a lack of pedological development. In other words, the C horizon is the unconsolidated material underlying the solum (A and B horizons). It may or may not be the same as the parent material from which the solum formed. The C horizon forms by breaking of  rocksinto smaller particles. The C horizon is below the zones of greatest biological activity and it has not been sufficiently altered by soil genesis to qualify as a B horizon.