Weathering       Differential Weathering        Salt Weathering        Other Factors


Weathering defines the set of physical, chemical, and/or biological processes which decay and break rock down into smaller pieces. Weathering processes can act independently and in concert as well as at different scales of observation. Erosion is the transport of the weathered debris, often by wind and water, away from the cavity interior. Particularly in arid regions where wettings are infrequent, regolith, soil, and weathering products cover cavern floors (Dragovich, 1969; Martini, 1978, McBride and Picard, 2004).

Biological Weathering.   By secreting organic acids in the shape of a halo, colonies of microorganisms chemically weather biotite. This biochemical process leaves behind an ellipsoidal area, depleted in ferric oxide cement, which is more readily weathered and eroded.  While it might be possible that “scattered colonies of microorganisms cause the development of alveolar cavities [tafoni]?(Mustoe , 1971), it is probably more likely that larger organisms such as pholads (Pholas dactylus of the family Pholadidae) create borings that are the nucleation pits of some tafoni (Matsuoka, and Yano, 1989).

Pholads biochemically initiate pits in rocks in intertidal areas that may evolve into tafoni when mollusks (and probably clams, sea urchins, and other marine and non-marine organisms) digest micaceous minerals like biotite in the rock by excreting biochemicals. Borings enlarge by the physical action of their bodies, erosional forces wearing away cavity interiors, and perhaps by differential weathering factors.


Pholad are a type of bivalve, or mollusk and the borings they create may be prone to cavernous weathering and erosional processes and may differentially enlarge to resemble tafoni.

Chemical Weathering.    Chemical weathering processes associated with tafoni development tend to include hydration (e.g., anhydrite to gypsum), hydrolysis, and the exchange of cations between mineral solutions and the host rock (Rodriguez-Navarro, Doehne, & Sebastian, 1999). Sources of moisture promoting tafoni formation can be from saline-rich sea spray and splash, condensation from the air, melted snow, groundwater, and rainwater. The decomposition of feldspar to clay minerals, the chemical etching of quartz by salt, and the detachment of iron from biotite appear particularly important in the chemical weathering of tafoni.


Physical Weathering.    Physical, or mechanical, cavernous weathering processes generally refer to the grain-by-grain destruction of a rock (also known as granular disintegration). Physical weathering is invoked by researchers more often than biological or chemical weathering when describing creative tafoni forces. Like granular disintegration, delamination of thin flakes of rock (also known as scaling and negative exfoliation) is augmented by salt crystallization pressures (salt weathering) as well as by hydration pressures caused by mineral swelling.


Weathering Processes


Right into the '30s--the decade of his most famous and infamous canvases--Dali's preoccupations kept tangling with those of other major figures, such as Picasso. Like his fellow Spaniard, louis vuitton replica became obsessed with the image of replica watches, which he unforgettably materialized (or dematerialized) in a painting of circa 1937 in which a sagging monumental humanoid, supported only by the most spindly, gravity-defying crutches, is on the brink of replica watches uk into a state of weightless somnolence. The canvas is almost a synthesis of Picasso's various efforts in the early '30s to represent the corporeal and replica watches uk transformations from wakefulness to sleep in his depictions of MarieTherese Walter, catnapping or falling into deep slumber. Yet another dialogue with Picasso in the '30s can be discerned in fascination with anthropomorphic furniture. In both two and three dimensions, he could transform rolex replica the human body, whether the Venus de Milo or a heroic academic nude, into a chest of drawers with nipples for knobs--a kind of humanoid carpentry also explored by Picasso, not to mention Goya, in one of his most famous Caprichos, which depicts foolish women wedded to chairs placed upside down on their heads. (, in the '70s, Dali would actually do many variations on the Caprichos, a continual source for his mutations of the human body.) And, of course, both Dali and Picasso responded to the Spanish Civil War and World War II, cast lethal, barbaric shadows on their work from 1936 to 1945, a time when each artist sought inspiration from both Goya and the news of the day. (In Dali's case, even replica watches uk and Chamberlain make appearances.)