Tafoni

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Tafoni are cavities that form in granular rock. They can be tiny or very large, and have smooth, curved walls with rounded openings. Many tafoni occur in groups on rock faces.

There are several subtypes, such as honeycomb, alveolar (very small), sidewall, basal, nested, and relic tafoni. In Italian they’re often called nido d’ape roccioso. The word’s origin isn’t certain; it may come from Greek or Italian roots. The term started appearing in 1882.

Tafoni usually appear on natural or manmade rock faces that are vertical or steep, especially in sandstone or granite, but they can form in other rocky materials as well. They’re found in all climates but are most common where salt is present and drying conditions are frequent, like deserts and coastal areas. They occur worldwide, including famous places in India’s Thar Desert, Petra in Jordan, coastal California, Australia, and even Arctic and Antarctic regions.

What shapes their formation is not settled. Many ideas have been proposed, including marine wear, wind, temperature changes, and chemical weathering under a protective crust. Biogeochemical effects from lichens and salt-related processes have also been suggested. Since the 1970s, salt weathering has been a leading explanation, and today scientists think tafoni result from several interacting physical and chemical processes, including salt weathering and cycles of wetting and drying.