The USDA Soil Orders

Clay-rich soil characterized by the presense of large amounts of swelling clays

Dryland soil with little organic matter and little leaching of nutrients, lots of salts

Soil of recent orgin. Soil horizon formation limited to thin A horizon.

Soil containing permafrost close to the surface

Soil formed from volcanic ash

Ancient soil defined by heavy weathering, oxidation of iron in sediment

Soil dominated by buildup of organic matter

Soil of recent orgin. Soil formation limited to A and a B horizon

Soil dominated by thick and dark A horizon, relative lack of leaching of nutrients, grassland environments

Leached soil poor in nutrients and highly acidic most present in coniferous forests

Old soil with heavy weathering, heavy accumulation of clays below the surface. Frequent reddish color due to oxidation

Soil with accumulation of clays below the surface and somewhat leached, though not to the extent of older soils elsewhere