Geology Reference
In-Depth Information
(a)
(b)
Figure 8.12.
(a) Acuminate and ensiform residual, Mt Manypeaks area, near Albany, south coast of Western
Australia. (b) Hourglass-shaped rock, Murphys Haystacks, west coast of Eyre Peninsula, South
Australia.
(a)
Figure 8.13.
Pedestal or mushroom-shaped rock in granite (a) Sierra Guadarrama, central Spain.
exceptions. Most basal fretting is caused by soil moisture, and the resultant notches, like flared
slopes, provide a measure of recent soil erosion.
All-round attack of boulders or columns has produced fastigiate or conical residuals known as
Chinaman's, or coolie, hats (see
Fig. 8.10d).
Acuminate (or pointed) and ensiform (or blade-like)
boulders (Fig. 8.12a) are probably of similar origin, as are hourglass forms or dumb-bells (Fig. 8.12b),
which vary from the pointed forms only in the degree of the concavity developed. Mushroom or
pedestal rocks (Fig. 8.13) are other variants, and there are, in addition, several rocks that are named
from their resemblance to specific objects, for example, anvil rocks (Fig. 8.13d) (see also Chapter 9).
