12 Soil Orders

Alfisols

moderately weathered, forest (northern and midwestern US)

Andisols

volcanic ash; high porosity, particle surface area, water

Aridisols

very dry; insufficient moisture to produce enough organic matter (southwestern us)

Entisols

newly formed; recent soils that show little evidence of soil formation (little to no development)

Gelisols

Frozen; dark organic surface layer under permafrost (Alaskan tundras)

Histosols

Organic Wet; dark, slightly decomposed soil derived from grasses, leaves, and woody materials; very poorly drained (low

Inceptisols

slightly developed, young soils; beginning to show soil formation (wide range of temps and moisture environments)

Mollisols

deep fertile, prairie, dark soft soils; dark surface horizon, base saturation above 35% (prairie soils of the Great Plains)

Oxisols

very weathered; deep red/yellowish soils of humid, tropic, or subtropic areas (Hawaii and Puerto Rico)

Spodosols

Sand acidic; aluminum, iron, and humus have moved into B horizon, commonly have a coniferous tree cover (Eastern & Lake states, pacific northwest, and alaska)

Ultisols

Weathered; similar to alfisols, base saturation is 35% or less; clay

Vertisols

Shrinks and swells/ Dark, swelling, cracking clays; soils high in 2:1 clays that shrink and swell enough to mic the horizons (black belt soils of Mississippi Delta and Texas)