Muck is an organic soil in which most of the plant material is heavily decomposed and there are still a few recognizable plant fragments. Peat is an organic soil in which most of the plant material is still identifiable. Mucks are usually black, while peats may range in color from brown or reddish brown to black. Many organic soils emit an odor of rotten eggs, resulting from the partial decomposition of plants under waterlogged conditions. Soils composed predominantly of mineral matter, such as sand, silt, clay, or loam, are known as mineral soils.
Prolonged saturation leads to the development of gleyed or mottled soils.
Gleyed soil horizons are gray to greenish or bluish gray in color. Soils that are gleyed up to within 18 inches of the surface are hydric soils. Mottled soil horizons form in locations where the water table fluctuates over the course of the year. Soils which contain brown or yellow mottles within a grayish matrix are hydric soils when the mottling occurs within 18 inches of the surface. Soil series may be selected based on various geographic areas of responsibility or use, series status, various dates, or the soil classification.