Salt Weathering in Deserts

Abstract

WEATHERING of rocks as the result of pressures exerted by the crystallization of salts from solutions in confined spaces has been recognized for many years. Studies of crystal growth pressures have been summarized by Buckley¹. The roles of such pressures in rock weathering have been described by Birot², and analysed by Wellman and Wilson³, who stated that for rocks of equal mechanical strength those with large pores separated from each other by microporous regions are most liable to salt weathering. The process is pronounced in desert and coastal areas. It is likely to be most effective (i) in the humid deserts of western littorals where the supply of salts from fogs and chemical weathering is accompanied by frequent wetting and drying of the surface, and (ii) around the margins of playas and along channels in desert areas where salts tend to be concentrated and wetting and drying is most frequent. We accept the effectiveness of salt crystallization pressures, the Salzsprengung of German authors, but we suggest that there are two additional factors associated with salts which may lead to the disintegration of rock: (i) stresses exerted by the expansion of many salts in confined spaces as they are heated, and (ii) stresses caused by hydration of certain salts in confined spaces.