ABSTRACT
This chapter deals with the chemical, physical, and biological processes that weather rocks to produce debris ranging in size from coarse boulders, through sands and silt, to colloidal clays and solutes. It sets out the chief physical or mechanical weathering processes: unloading (the removal of surface cover), frost action, alternate heating and cooling, repeated wetting and drying, and the growth of salt crystals; the chief chemical weathering processes – solution or dissolution, hydration, oxidation, carbonation, hydrolysis, and chelation; and biological weathering, which is the chemical and mechanical action of animals and plants. It then proceeds to discuss weathering landforms, including large-scale cliffs and pillars, and smaller-scale rock-basins, tafoni, and honeycombs. The chapter looks at the strong influence that joints have on many weathering landforms, including those formed on granite, characteristic forms of which include bornhardts and tors. Lastly, it examines how weathering processes attack historic buildings and monuments, including the Parthenon and St Paul's Cathedral, and weathering as a factor in understanding the occurrence of some human diseases.
