Tafoni (singular: tafone) are cavities that develop in granular rock.
Although there are various definitions in the scientific literature, tafoni are commonly defined as small (less than ) to large (greater than ) cavity features that develop in either natural or manmade, vertical to steeply sloping, exposures of granular rock (i.e., granite, sandstone) with smooth concave walls, and often round rims and openings. Recognized subcategories of tafoni include ''
honeycomb
A honeycomb is a mass of Triangular prismatic honeycomb#Hexagonal prismatic honeycomb, hexagonal prismatic cells built from beeswax by honey bees in their beehive, nests to contain their brood (eggs, larvae, and pupae) and stores of honey and pol ...
'', ''stonelace'', ''alveolar'' (less than ), ''sidewall'', ''basal'', ''nested'', and ''relic tafoni''. It is also commonly synonymous with ''nido d’ape roccioso'' in Italian.
[Paradise, T.R., 2013. ''Tafoni and other rock basins.'' In: Shroder, J. (Editor in Chief), Pope, G.A., (Ed.), ''Treatise on Geomorphology.'' Academic Press, San Diego, CA, vol. 4, Weathering and Soils Geomorphology, pp.111–126.]
The
etymology
Etymology ( ) is the study of the origin and evolution of words—including their constituent units of sound and meaning—across time. In the 21st century a subfield within linguistics, etymology has become a more rigorously scientific study. ...
of the word ''tafoni'' is unclear. Tafoni may come from the
Greek word ''taphos'', ''tomb'', or it may stem from a
Corsican or
Sicilian word for ''holes'', ''taffoni'', or from ''tafonare'' meaning ''to perforate''. The earliest known publication of the term ''tafoni'' was in 1882.
[Hans Henrik Reusch (1882) ''Notes sur la géologie de la Corse'' (''Notes on the geology of Corsica''), ''Bulletin de la Société géologique de France'', 3rd series, 11 : 53-67 ; see p. 65]
From p. 65:
''"Le peuple appelle ces cavités, quand elles sont petites, des ''tafoni'' ; quand elles sont grandes, des ''grotte''."'' (People call these cavities, when they're small, ''tafoni'' ; when they're large, ''caves''.)
Distribution
Tafoni often occur in groups that can riddle a hillside, cliff, or other rock formation. They typically develop in
siliceous, either coarse-grained (
sandstone
Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
) or coarsely crystalline (
granite
Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...
), rock types. They also have been observed in
lacustrine silt
Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...
s,
tuffs, and
conglomerates. They can be found in all climate types, but are most prolific in salt-rich environments, such as deserts and coastal zones. They have been found across the Earth, with dramatic forms found in the
Jodhpur-
Ajmer
Ajmer () is a city in the north-western States and union territories of India, Indian state of Rajasthan. It serves as the administrative headquarters of the Ajmer district and Ajmer division. It lies at the centre of Rajasthan, earning it the ...
section of
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
's
Thar Desert,
Petra
Petra (; "Rock"), originally known to its inhabitants as Raqmu (Nabataean Aramaic, Nabataean: or , *''Raqēmō''), is an ancient city and archaeological site in southern Jordan. Famous for its rock-cut architecture and water conduit systems, P ...
,
Jordan
Jordan, officially the Hashemite Kingdom of Jordan, is a country in the Southern Levant region of West Asia. Jordan is bordered by Syria to the north, Iraq to the east, Saudi Arabia to the south, and Israel and the occupied Palestinian ter ...
, Coastal
California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
, and
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, and even in the
Arctic
The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...
regions and
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
. The common factors in the environments in which they are found are high salt concentrations and frequent or occasional desiccating conditions.
[Turkington, A.V. and Phillips, J.D., 2004. ''Cavernous weathering, dynamical instability and self‐organization.'' ''Earth Surface Processes and Landforms'', 29(6), pp.665-675.]
Origin
Many explanations have been proposed for the origin of tafoni. They include marine abrasion; wind corrosion; mechanical weathering resulting from short-term temperature variations; chemical weathering of the interior of the rock (
core-softening) under a protective crust (
case-hardening
Case-hardening or carburization is the process of introducing carbon to the surface of a low-carbon iron, or more commonly a low-carbon steel object, in order to Hardened steel, harden the surface.
Iron which has a carbon content greater than ~ ...
) followed by mechanical removal of the softened material; biogeochemical weathering by lichens; temperature variations acting on salt efflorescence in coastal regions; and
salt weathering. Starting in the 1970s, most workers have advocated salt weathering as the primary explanation for the formation of tafoni. Currently, tafoni are considered to be polygenetic in origin being the result of complex interaction of physical and chemical weathering processes, which include salt weathering and cyclic wetting and drying.
[McBride, E.F. and Picard, M.D., 2000. ''Origin and development of tafoni in tunnel spring tuff, Crystal Peak, Utah, USA.'' ''Earth Surface Processes and Landforms'', 25(8), pp.869-879.]
File:Tafoni-davis_hg.jpg,
Image:Tafoni-san-francisco.jpg,
File:Buntsandstein Waben.jpg,
File:Tafoni at Elgol, Isle of Skye.jpg,
File:HoneycombWeatheringCambrianIsrael.jpg,
File:Korea-Mokpo Gatbawi 11-01716.JPG, Tafoni formations, named Gatbawi (Hat Rock), found on the shore of Mokpo
Mokpo (; ) is the List of cities in South Korea, third largest and most densely populated city in South Jeolla Province, South Korea, located at the southwestern tip of the Korean Peninsula, close to Yudal mountain. Mokpo has frequent high-speed ...
's east harbor, near the mouth of the Yeongsan River, South Jeolla Province
South Jeolla Province (), formerly South Chŏlla Province, also known as Jeonnam (), is a province in the Honam, Honam region, South Korea, and the Provinces of Korea, southernmost province in mainland Korea. South Jeolla borders the provinces of ...
, South Korea
South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...
.
File:Tafoni_weathering_in_monzonite_near_Corbara_in_Corsica.jpg, Tafoni on the shore of Corsica.
File:Tafoni_in_granite_near_Corte_in_Corsica.jpg, Tafoni in the mountains of Corsica.
File:Tafoni_in_conglomerate_near_Palasca_in_Corsica.jpg, Tafoni in conglomerate rock, Corsica.
See also
*, a similar weathering landform
References
External links
www.tafoni.comComprehensive explanation of tafoni, explanations of how they form, images, references
Gallery of tafoni along California's Central Coast
{{Commons category
Rock formations
Weathering landforms