A type of weathering that is most active in arid environments, where there is little precipitation and a high rate of evaporation. Precipitation fills voids and crevices with water, which dissolves salts from the adjacent rock. As the water evaporates, the salts crystallize. Subsequent heating or hydration causes the crystals to expand, widening the spaces they occupy and detaching loose rock fragments that are washed away with the dissolved salts the next time it rains.