Geology Reference
In-Depth Information
(a)
(b)
Figure 8.14.
Piedmont angle or nick (a) at base of nubbin at Naraku, northwest Queensland. (b) Base of
inselberg in the western Sahara
8.3
SCARP-FOOT WEATHERING AND EROSION, AND THE PIEDMONT ANGLE
One of the contrasts between the arid and semi-arid landscapes of low and middle latitudes, and
others, say from the humid mid-latitudes, is that in the former there is an abrupt transition from hill
to plain (Fig. 8.14). This sharp break of slope is called the piedmont angle or nick. It has long
excited the attention and interest of geologists and geomorphologists and various explanations for
it have been advanced. Some have suggested that it marks the junction between adjacent fault
blocks, and though the presence of zones of dislocation may assist in and enhance its formation,
the piedmont angle is most commonly and well-developed in areas devoid of faults. The feature
has been explained as due to lateral undercutting by streams debouching from uplands on to plains,
