Large areas of Histosols are found in the circumpolar region of the northern hemisphere, as well as in Southeast Asia.
Histosols are formed in 'organic material' with physical, chemical and mechanical properties that differ strongly from those of mineral soil materials. Organic soil material accumaulates in conditions where plant matter is produced by a climax vegetation and where decomposition is slow.
Soils having a histic or folic horizon (wet or dry organic horizons, respectively)
either 10 cm or more thick if overlying a lithic or paralithic contact, or
40 cm or more thick and starting within 30 cm from the soil surface.
Histosols do not have an andic or vitric horizon that starts within 30 cm from the soil surface.
Highland peat in western Ireland (Ombri-Sapric Histosol)
Strongly decomposed peat under cultivated grassland, the Netherlands (Rhei-Sapric Histosol)