The pitted and pocked Vaqueros sandstone of Goat Rock
Vaqueros Sandstone

Tafoni: are they formed by weathering processes alone or are organisms involved?

Just a few steps “downstairs” from the top of Goat Rock, hikers get to a point on Ridge Trail from where a short path leads to and ends in front of amazing variations of erosional surface patterns. The sunset-facing overhang and walls of Goat Rock are shaped by a network of tafoni: fractal geometry on fractal sandstone. The Italian word tafone (plural tafoni) means “cave” or “cavern.” At the nearby interpretive shelter these small cave-like features are described as being the result of complex weathering processes occurring over centuries on the surface of the Vaqueros sandstone at Castle Rock. How well are these physical and chemical weathering processes understood? Tafoni origin and evolution is still a geologic mystery. But some theories try to explain Tafoni formation. And then there are bivalves that just do it! At Palomarin Beach, for example, I came across mollusk-sculpted foreshore cobbles: tafoni made by rock-boring clams.
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