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navigate by keyword : apart asvertisols can causing clay clays content cracked cracks create dry enough expand get have high interstructural known large make millions mineral minerals molecules moves out place presence pushes removed shrink shrinkswell shrinking smectite smectites soil soils some space spaces structural swellwhen takes units volume water wet

Some soils have a high content of clay minerals known as smectites. When smectite clays get wet, water moves into a space between the structural units that make up the clay mineral. The presence of the water molecules pushes the structural units apart, causing the clay mineral to expand, or swell. When these clays dry out, the water molecules are removed from the inter-structural spaces and the clays shrink. When this shrinking takes place in millions of clay structural units in a volume of soil, the shrinking can be enough to create large cracks in the soil. Soils with a high shrink-swell clay content are known asÃâÃÂ Vertisols.