Vertisolic soils develop in fine-textured soil materials with >60% clay, of which at least half must be montmorillonite. The dominant soil-forming processes in Vertisols are: cracking, argilli-pedoturbation (mixing of clay in the pedon) and mass movement of materials due to shrinkage and swelling of clays during drying/wetting cycles. These soils have two characteristic horizons (either B or C): slickensides (ss = clayey subsurface horizons which have polished and grooved ped surfaces -‘slickensides’, or wedge-shaped structural aggregates ) and vertic (v = horizon with deep and wide cracks when dry, that allow the surface material to fall down the cracks causing the soil to heave). The wetting and drying cycles cause the clays to expand and contract.