Tafoni

Tafoni are cavities that develop in granular rock, ranging from less than a centimeter to more than a meter across, forming in natural or artificial vertical to steeply sloping exposures of rock such as granite or sandstone. They typically have smooth, concave walls and often rounded rims and openings, and several recognized subtypes exist, including honeycomb, stonelace, alveolar, sidewall, basal, nested, and relic tafoni; geologists generally attribute their formation to some form of salt-weathering, or haloclastic, control.