Geology Reference
In-Depth Information
prominent. The hills vary in size and shape. Some are low, elongate and elliptical in plan and are
called whalebacks or dos de baleine
(Fig. 6.3c)
.
Those that are more nearly elliptical in plan and
have steep bounding slopes are known as turtlebacks. A few are high, asymmetrical in profile and
with little imagination reasonably called elephant rocks (dos d'elephant). Many have plan axes of
similar length, approximately equal to the height of the crest abve the adjacent plains and they are
referred to as domes or half-oranges. The many local names - matopos, r uwares, morros, dwalas,
meias laranjas, demi-oranges, moas, navas, medas, yelmos and so on - provide some indication of
the wide distribution of this basic form.
Some bornhardts stand in isolation (Fig. 1.2e) and others occur in small groups (Fig. 1.2b), but in
contrast with these detached forms there are ranges or massifs that comprise ordered repetitions of the
domical form. Thus, the Ev erard Range, in the nor th of South Australia, and the Kamiesber ge of
central Namaqualand, each consists of a lar ge number of closely juxtaposed bornhardts arranged in
ordered rows (Fig. 6.4). In these landscapes each dome is developed on a joint block, but is neverthe-
less part of a larger massif. Thus, many inselbergs are bornhardts, but not all bornhardts are inselbergs.
Some granitic inselbergs are block- or boulder-strewn and are called nubbins or knolls, and yet
others are angular and castellated and are kno wn as castle koppies. Neither is as frequentl y and
widely developed as the domed variety. These forms appear to be variations on the bornhardt theme,
(a)
(b)
Figure 6.4. (a) Map of part of the Everard Ranges, northern South Australia (drawn from air photographs),
showing or thogonal fracture system. (b) The development of a bor nhardt on each fracture
defined block.
