| Soil formation is the process by which rocks are broken down into progressively smaller particles and mixed with decaying organic material. Bedrock begins to disintegrate as it is subjected to freezing-thawing cycles, rain, and other environmental forces (I). The rock breaks down into parent material, which in turn breaks into smaller mineral particles(II). The organisms in an area contribute to soil formation by facilitating the disintegration process as they live and adding organic matter to the system when they die. As soil continues to develop, layers called horizons form (III). The A horizon, nearest the surface, is usually richer in organic matter, while the lowest layer, the C horizon, contains more minerals and still looks much like the parent material. The soil will eventually reach a point where it can support a thick cover of vegetation and cycle its resources effectively (IV). At this stage, the soil may feature a B horizon, where leached minerals collect. |
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