Abstract
The article is a case study of the development of cavernous weathering forms (alveoli and tafoni) on a sea cliff near Keflavik on the Reykjanes peninsula in southwestern Iceland. The majority of forms are found on vertical or inclined rock faces and cluster around the uppermost edge of the cliff. Single hollows gradually evolve due to back wearing of their sidewalls into complex caverns, until finally the whole outermost layer of basalt is removed. Particular attention is paid to mineralogical changes of basalts due to chemical and salt weathering. Chemical decomposition of feldspars, pyroxenes and olivines followed by precipitation of iron on and within the weathering rind, the presence of micro- and macro-pores such as gas bubbles and delivery of marine salts are proposed to be the key factors influencing cavern development.