Twelve Soil Orders
Well-developed mineral soils
alfisols, aridisols, mollisols, oxisols, ultisols, spodosols, vertisols
Weakly developed soils
andisols, entisols, inceptisols
Characterized by maturity (6)
entisols, inceptisols, alfisols, ulitisols, spodosols, oxisols
organic soils
gelisols, histosols
Characterized by climate (3)
mollisols, aridisols, gelisols
ultisols
Highly weathered soils in tropical and subtropical environments that have low base content and a subsurface horizon rich in eluviated clay.
oxisols
Highly weathered soils in tropical environments that have low base status and subsurface horizon that has a high oxide concentration.
entisols
Horizonless soils usually formed within recently deposited sediments.
gelisols
Largely organic soils that form in extremely cold environments where permafrost is thick. Due to repeated freezing and thawing, soil horizons and surface expression are chaotic.
spodosols
Soils in cool, moist environments that thave a B horizon rich in eluviated sesquioxides.
aridisols
Soils in dry climates that are low in organic matter and frequently have subsurface horizons rich in calcium carbonate or soluble salts.
mollisols
Soils in semi-arid/subhumid grasslands in midlatitudes that have humus-rich A horizon and a B horizon that has a high base status.
alfisols
Soils with high-base-content B horizon rich in eluviated clay. Found from low to subarctic latitudes.
inceptisols
Soils with poorly developed horizons, but which may evolve further.
vertisols
Tropical and subtropical soils with high base status that contain an abundant amount of expandable clay that swells when wet and shrinks when dry.
histosols
Very dark soils consisting mostly of organic matter. Typically found in cool/moist environments where organic decompostiton is slow.
andisols
Weakly developed soils formed within glassy volcanic sediments ejected by active volcanoes.
Characterized by parent material (3)
vertisols, andisols, histosols