The cliff face is often a zone of rapid weathering due to the array of processes that can attack it. Physical weathering includes frost action and the growth of salt crystals in pores. Chemical weathering must involve hydration and hydrolysis, together with the effects of brine. Biological weathering is important too, with the growth of lichen and the large amounts of guano deposited on cliffs like those of Noss. The products of weathering and the weakened rocks are quickly removed by storm wave action and spray to leave roughened surfaces in which the variable resistance of the rock units can be further etched out.

The influence of spray extends high on the cliff and sometimes onto the cliff top. Stripping of vegetation and regolith exposes bedrock to a range of weathering processes and occasional scouring during storms removes the loosened rock. The zone of wave scour is indicated by the absence of vegetation from the cliff face and top.

 

Cliffs: weathering

Noss. Etching out of bedding planes and joints by weathering processes and marine erosion

Bard, Bressay. Weathering of Devonian sandstone, with case hardening and removal of disaggregated sand