Soils may have accumulations of soluble salts due to restricted leaching. Arid regions, deserts and near deserts. In dry periods these soils develop wide, deep cracks. Form in old marine deposits. Mollisols Mineral soils with thick, dark colored, not highly leached surface horizon.
Soils generally form under prairie vegetation.
Histisols Organic soils, properties due primarily to organic matter, not mineral matter. Wet, boggy or swampy conditions. Relationships Among and Within Soil Orders Orders do not fall nicely into a sequence. Orders occur in widely different climates and can show major profile differences. Interpreting Soil Characteristics from Names Suborder, great group, and subgroup names can be used to supply useful information about specific soils.