Vertisols
Vertisols (from Latin verto, "turn") are clay-rich soils that shrink and swell with changes in moisture content. During dry periods, the soil volume shrinks and deep wide cracks form. The soil volume then expands as it wets up. This shrink/swell action creates serious engineering problems and generally prevents formation of distinct, well-developed horizons in these soils. They are divided into six suborders: Aquerts, Cryerts, Xererts, Torrerts, Usterts and Uderts.
Globally, Vertisols occupy approximately 2.4% of the ice-free land area. In the U.S., they occupy approximately 2% of the land area and occur primarily in Texas.
Vertisols have: (1) a layer at least 25 cm thick that has slickensides or wedge-shaped peds with tilted long axes; and (2) at least 30 percent clay in all horizons to a depth of 50 cm; and (3) cracks that open and close periodically. (USDA-NRCS image)
