Desiccation structures (mud cracks, etc.)
Desiccation structures originate as shrinkage cracks formed by the evaporation of water from the surface of clay-rich sediment. Previously called mud cracks, they are of subaerial origin, and are caused by the slow drying-out of muddy sediments which have been exposed to the action of sun and wind. The volume decrease that results from this loss of fluid gives rise to tensile stresses distributed equally in all directions within the bedding plane, that are relieved by the formation of a characteristic pattern of open polygonal cracks on the surface of the sediment.
Arrays of polygonal cracks resulting from this process are commonly seen on dried-out surfaces in puddles and slurry pits, around the margins of lakes, reservoirs and playas, and on tidal mudflats. Where well-developed, the desiccation structures form striking prismatic columns a few centimeters to several meters across, separated by deep fissures, and divided internally into secondary sets of cracks. Following a change in...
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