Frans J.P.M. Kwaad,
physical geographer
This website is about the mechanism of salt weathering.
Salt weathering is a form of mechanical or physical weathering of rock. No chemical alteration of rock constituents is involved in salt weathering. The salt derives from an external source (capillary rising ground water, eolian origin, sea water along rocky coasts, atmospheric pollution). Salt weathering is favoured by dry conditions, such as are found in warm and cold (arctic) arid climates. Salt weathering (salt damage, salt decay) also occurs on buildings and monuments in arid climates as well as under dry microclimatic conditions in humid climates. Corrosion by sea water (marine corrosion, aqueous corrosion) is not a mechanical but an electrochemical process.
Rock breakdown by salt weathering takes place through salt crystal growth in rock pores and/or through hydration of hydrate forming salts, like sodium sulphate (Na2SO4 -> Na2SO4.10H2O). The expanding salt crystals exert a pressure on the walls of the rock pores that exceeds the tensile strength of the rock. In the following paper a series of experiments with a climatic cabinet is described and discussed aimed at elucidating the mechanism of salt weathering. The experiments were carried out at the Department of Physical Geography and Soil Science, University of Amsterdam, The Netherlands.
Here is an example of salt weathering of granite at the French Mediterranean coast near St. Tropez.
In the following pictures, details are shown:
Developing salt crust through evaporation of salt brine in the surf
zone.
Crystallized salt on the rock surface and in rock fissures in
granite in
the surf zone.
Rock particles released by salt weathering of granite in the surf
zone.
Rock particles released by salt weathering of granite in the surf
zone.
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