Vertisol
In Pedology or science of the ground, the vertisol is a ground rich in clay of type 2/1 i.e. containing a layer of aluminum oxide enclosed by two layers of silica tetrahedrons. It is about smectite which includes/understands in particular the " type; Montmorillonite ". One finds besides, in a little old literature, the " term; montmorillonite" to characterize clays of the vertisols. It is known now that they are often types close to montmorillonite but with Fer in the crystal lattice.
The main thing is that the Smectite S are clays which inflate or deflate according to their water content. The vertisols are thus affected slits of withdrawal to the desiccation (photo) and phenomena of pressure to swelling what causes the surface undulation of the ground (relief gilgaï). These grounds thus are adapted little to constructions! They are difficult to work but productive. One finds them in Mediterranean medium (ex: Sicily) and tropical dryness (ex: Chad). By inflating and retracting the layers of clays trap a little organic matter so that these very characteristic clay soils are often brown dark or even completely black.
Bibliography: LEGROS J.P., 2007. Large Grounds of the World , Polytechnic Presses and French Academics. 574 p.
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