Tafoni are ellipsoidal, pan- to bowl-shaped, natural rock cavities. These cavernous weathering features include tiny pits, softball-sized cavities, truck-sized caves, and nested and cellular honeycomb forms. Tafoni typically develop on inclined or vertical surfaces and occur in groups. These exquisite and fascinating cavernous weathering landforms are present on the surfaces of many different kinds of rocks located in a multitude of geographic regions around the world. Since the late 1800s, more than 100 research articles have been published in numerous languages on this geomorphic topic. Despite the peaked interest, tafoni formation is puzzling and continues to arouse curiosity (Smith, 1982).

Tafoni-like features comprise a class of relatively deep, rounded to elongated natural rock cavities bored primarily by rock weathering processes and secondarily by erosional processes. In the geological literature, the distinction between cavernous weathering features is muddled. I think tafoni like structures include small tafoni, pits, hollows, niches, recesses, alcoves, alveoles, alveolar weathering, weathering pits, gnammas, stone fretting, fretwork, recesses, honeycomb, and honeycomb weathering. Geomorphologists point to salt weathering, differential cementation, lithologic variation, and micro-climate mediated differential weathering processes, as important controls the development of these rounded, cave-like rock structures.

On geologic time-scales, tafoni cause rapid coastal landscape retreat, while desert landscapes retreat more slowly. Gill, Segnit, and McNeil (1981) estimate that tafoni weathering processes cause 10 percent of all coastal retreat. On human time-scales, tafoni destroys important stone monuments and sea walls. See these time-series photographs for evidence of change. Researchers emphasize understanding more about this rock weathering phenomenon to prevent or slow the decay of invaluable stone structures.