Caves and tafoni - Landforms and Geology of Granite Terrains - page 236

(a)

(b)

Figure 10.4. (a) Open shelter or alcove occupying void left by evacuation of joint-defined block, at base

of granite tor, or castle koppie, on Dartmoor, southwestern England (Geological Survey
Museum, UK). (b) Poorly developed visor on shelter at Mt Hall, northwestern Eyre Peninsula,
South Australia.

and due to basal sapping, to the exploitation of intersecting fractures (or the removal of the joint
blocks so defined), are also widely developed (e.g. Fig. 10.4).
Ve ry small hollows are called alveoles, hence alveolar weathering (Mustoe, 1982). Alveoles can
form quickly, for some have already developed on a seawall constructed of greywacke (sandstone)
on the Victorian coast in 1943.
When alveoles are associated in numerous groups on the interior walls of tafoni, many authors
refer to them as honeycomb weathering ( Fig. 10.5) . The disappearance of this honeycomb struc-
ture in the very well evolved tafoni and the substitution of it by a scalloped surface ( Fig. 10.6b)
suggest that honeycomb development is an early stage of tafoni evolution process. Generally, the