Geology Reference
In-Depth Information
(a)
(b)
Figure 5.7.
(a) Geikie's (1894, p. 15) sketch showing corestones set in weathered granite: (i) solid granite,
(ii) corestones in grus, (iii) soil, (b) The two-stage development of boulders: (i) differential fracture-
controlled weathering beneath the surface, (ii) fracture pattern in section, (iii) differential erosion
of the differentiated mass, leaving the corestones as boulders.
Figure 5.8.
Chaotic mass of boulders, or compayrés, strewn over hillslope and crest of hill at Palmer, eastern
Mt Lofty Ranges, South Australia.
whatever the precise result, the exposure of the corestones by differential erosion is the second stage
in the development of boulders.
In an immediate sense, two distinct processes, weathering and erosion, are involved in the
formation of boulders and together they are frequently referred to as the two-stage process or
mechanism (Fig. 5.8), though the two are not necessarily separate and distinct in time. The first
