What is Tafoni?

➤ Jon Boxerman, author of www.tafoni.com, describes these beautiful landscape features for Tasmanian Geographic, and puts them in a global scientific context.

On the slopes of Mount Dromedary in the Derwent Valley

On the slopes of Mount Dromedary in the Derwent Valley

Introduction

Tafoni are ellipsoidal, pan- to bowl-shaped, natural rock cavities. These cavernous weathering features include tiny pits, softball-sized cavities, truck-sized caves, and nested and cellular honeycomb forms. Tafoni typically develop on inclined or vertical surfaces and occur in groups. These exquisite and fascinating cavernous weathering landforms are present on the surfaces of many different kinds of rocks located in a multitude of geographic regions around the world. Since the late 1800s, more than 100 research articles have been published in numerous languages on this geomorphic topic.

Small tafoni can be found below the Octopus Tree on Mt Wellington

Small tafoni can be found below the Octopus Tree on Mt Wellington

Tafoni-like features comprise a class of relatively deep, rounded to elongated natural rock cavities bored primarily by rock weathering processes and secondarily by erosional processes. In the geological literature, the distinction between cavernous weathering features is muddled. Tafoni structures include: small tafoni, pits, hollows, niches, recesses, alcoves, alveoles, alveolar weathering pits, gnammas, stone fretting, fretwork, recesses, honeycomb, and honeycomb weathering. Geomorphologists point to salt weatheringdifferential weathering processes, lithologic variation, and micro-climates, as important factors on the development of these cave-like rock structures.

The Word “Tafoni”

Tafoni is the plural noun and adjective; tafone is the singular noun for a single cavern. Occasionally, researchers unnecessarily pluralize tafoni (i.e., tafonis) to name multiple tafoni.

 

A detailed view of Southern Tasmanian tafoni. On the slopes of Mount Dromedary in the Derwent ValleyOn the slopes of Mount Dromedary in the Derwent ValleyA detailed view of Southern Tasmanian tafoni. On the slopes of Mount Dromedary in the Derwent Valley

A detailed view of Southern Tasmanian tafoni. On the slopes of Mount Dromedary in the Derwent Valley

The origin of the word tafoni is unknown, but has Mediterranean origins. The word tafoni may stem from the Greek word taphos meaning tomb or sepulcher (Battisti and Alessio, 1957, after Twenhaile, 1992, pg. 44). Tafoni may also stem from a Corsican (French) word, taffoni, meaning windows, or from tafonare meaning to perforate (Wilhelmy, 1964). In Sicilian, tafoni means windows (Goudie, 2003). The earliest printed uses of the term “tafoni” may be credited to Reusch (1882) (after Dragovich, 1969) and Pench (1884), whom both described Corsican tafoni.

A rock climber clambers on tafoni near Sphinx Rock on Mount Wellington

A rock climber clambers on tafoni near Sphinx Rock on Mount Wellington

Charles Darwin (1839) may have first described tafoni while on the Beagle when passing through King George’s Sound in Western Australia. Though he thought the forms he discovered along the coastline were a product of calcareous casts of branches of trees or roots (Mustoe, 1982; Turkington and Paradise, 2004), scientists now know the eolianite he observed is a weathering product.

Darwin writes on Feb 7, 1836:

One day I accompanied Captain Fitz Roy to Bald Head; the place mentioned by so many navigators, where some imagined that they saw corals, and others that they saw petrified trees, standing in the position in which they had grown. According to our view, the beds have been formed by the wind having heaped up fine sand, composed of minute rounded particles of shells and corals, during which process branches and roots of trees, together with many land-shells, became enclosed.  The whole then became consolidated by the percolation of calcareous matter; and the cylindrical cavities left by the decaying of the wood, were thus also filled up with a hard pseudo-stalactical stone.  The weather is now wearing away the softer parts, and in consequence the hard casts of the roots and branches of the trees project above the surface, and, in a singularly deceptive manner, resemble the stumps of a dead thicket.”

Where Are They Found?

Tafoni are widely distributed around the world (and the solar system!) in diverse climates such as: temperate, humid, hot and arid, and frigid and arid regions, as well as at a range of elevations from sea level to more than 2,200 meters above mean sea level (in South America). Tschang (1974) and Mustoe (1982) present excellent accounts of their worldwide occurrences.

Despite the diverse environmental and geographic settings in which tafoni exist, there is general convergence in the literature that temperate near-shore environments and arid deserts (frigid or hot) are the most favorable locations for tafoni development.

On the slopes of Mount Dromedary in the Derwent Valley

The tafoni caves on the slopes of Mount Dromedary in the Derwent Valley

Where in Tasmania?

You can look for tafoni in sedimentary rocks, such as the Sphinx Rock or Octopus Tree onMount Wellington, or in Waterfall Valley or at the base of Cradle Mountain along tho Overland Track. Tafoni structures are also present in the granite boulders  at Freycinet National Park.

A detailed view of Southern Tasmanian tafoni. On the slopes of Mount Dromedary in the Derwent Valley

A detailed view of Southern Tasmanian tafoni. On the slopes of Mount Dromedary in the Derwent Valley

On the slopes of Mount Dromedary in the Derwent Valley

On the slopes of Mount Dromedary in the Derwent Valley

 Weathering Patterns

In the organic and inorganic realms of the natural world, a delicate balance exists between energy conservation, space, and time. Unifying themes among patterns appear in a plethora of different contexts in nature.

Peter Stevens (1974) describes recurring spatial themes in the natural world such as spiraling, branching, cracking, bursting, and packing patterns. Since natural systems and living beings tend to expend minimal amounts of energy to maximize motion, they tend to conform to utilize 3-D space as efficiently as possible. In so doing, similar forms repeat. It is within these unifying themes in nature  wherein lies a bounty of beauty and intrigue.

A detailed view of Southern Tasmanian tafoni. On the slopes of Mount Dromedary in the Derwent Valley

A detailed view of Southern Tasmanian tafoni. On the slopes of Mount Dromedary in the Derwent Valley

During evolution of the rock weathering pattern, new forms emerge including relatively shallow ellipsoidal hollows with thin walls, cavities with angular wall intersections, and cavern wall vestiges appearing as labyrinthine tendrils. Some researchers note additional forms associated with the tafoni pattern such as: convex walls, overhanging visors, and smooth, gently sloping floors. Many geologists also describe tafoni enlarging in an upward and backward direction.

Martian Tafoni.

Of all the locations tafoni exist, Mars may be the most unforeseen. Tafoni-like features on Martian outcrops suggest that weathering could be active or may have been once active billions of years ago (Smith, 1983; Rodriguez-Navarro, 1998). Images taken by Pathfinder (below) probably provided some justification for visiting Mars in search of water. The photograph below depicts honeycomb forms that may have formed long ago (~2 Ba) in the presence of moisture or perhaps these features represent holes vacated upon dislodgment of blueberry-like concretions or spherules.

The Martian rock outcrop named “Half Dome”. Images from the NASA Pathfinder mission to Mars (available at NASA)

You can learn more about Martian Geology at NASA Science.

To see some Tasmanian tafoni, click on over to the gallery of tafoni on Mount Dromedary Tafoni.