Tafoni are small cave-like features found in granular rock such as sandstone, granite, and sandy-limestone with rounded entrances and smooth concave walls, often connected, adjacent, and/or networked. They often occur in groups that can riddle a hillside, cliff, or other rock formation. Tafone is the name for one of the cavities, and tafoni is the plural.
The tafoni found at the posted coordinates are also called honeycomb weathering, cavernous weathering, stone lattice, or tafoni weathering. Scientists have proposed many ways this weathering could occur: wind erosion, frost shattering, or cold air blowing on sun-heated rocks. More recently, they have focused on mechanisms involving groundwater - either the groundwater dissolving the cement that holds the rocks together, or groundwater evaporating at the surface leaving behind dissolved minerals. Since this type of weathering is seen all over the world, in many climates, it is possible that no one mechanism explains all the occurrances.
They can be found in all climate types, but are most abundant in intertidal areas and semi-arid and ariddeserts. Explanations of their formation include salt weathering, differential cementation, structural variation in permeability, wetting-drying, and freezing-thawing cycles, variability in lithology, case hardening and core softening, and/or micro-climate changes and variation (that is, moisture availability). Tafoni have also been called fretting, stonelace, stone lattice, honeycomb weathering, and alveolar weathering.
Tafoni which starts along suhorizontal joints and grows upward is called basal tafoni. This sort of formation can lead to skylights. Tafoni that begins along vertical or near vertical joints are called sidewall tafoni. Fin shaped spires can eventually be undermined to produce windows and arches in such a process.
In order to log this earthcache, please email me the answers to the following questions:
1. Estimate the height of the rock formation at the posted coordinates.
2. What is the shape of these tafoni? How big are they? Would you describe this as a basal or sidewall tafoni?
3. What are the approximate dimensions (width, height, and depth) of the largest tafone that you see? Are there smaller tafoni inside it?
4. In your opinion , why do you think the tafoni appear only at this outcrop? How do you think they formed?
Congratulations to wvcachers3 on the FTF!