Gleysol

thumb|304x304px|Distribution of Gleysols A gleysol or gley soil is a hydric soil that unless drained is saturated with groundwater for long enough to develop a characteristic colour pattern. The pattern is essentially made up of reddish, brownish, or yellowish colours at surfaces of soil particles and/or in the upper soil horizons mixed with greyish/blueish colours inside the peds and/or deeper in the soil. Gleysols are also known as Gleyzems, meadow soils, Aqu-suborders of Entisols, Inceptisols and Mollisols (USDA soil taxonomy), or as groundwater soils and hydro-morphic soils.

The term gley, or glei, is derived from , and was introduced into scientific terminology in 1905 by the Ukrainian scientist Georgy Vysotsky. thumb|The clay on the right is exposed to air and is oxidized a reddish hue. The clay on the left is identical, but sealed in a glass jar for two weeks in an anaerobic setting, causing redox and color change to gley. Gleysols occur within a wide range of unconsolidated materials, mainly fluvial, marine and lacustrine sediments of Pleistocene or Holocene age, having basic to acidic mineralogy. They are found in depression areas and low landscape positions with shallow groundwater.