Twidale & Bourne: Geomorphology of The Humps, Hyden 
A 
Figure 12. (A) Elongate boulder with tafone at left end, 
and undercut lower margins. (B) Detail of tafone with 
markedly mamillated surface, shown in Fig 12A. The 
granite is weathered and crumbles to the touch. The 
feldspars are altered to kaolin. Hammer provides scale. 
many other massive outcrops in the vicinity. The 
Humps has been affected by earth movements. 
Evidence takes the form of an A-tent (have others 
been disturbed and used as small animal traps?), 
blisters or arches not yet with cracked crests, and 
several groups of slipped slabs and low angle 
fractures slicing though the crests of domical rises 
(cf Twidale & Sved 1978; Twidale & Bourne 2000). 
The formation of split rocks may have been 
hastened by seismic shaking. 
Other specific features 
Polygonal cracking and mogotes 
Spectacular groups of miniature mesas, or 
mogotes, capped by iron oxide indurations occur 
low on the western slope of King Rocks, some 20 
km east of The Humps (Twidale et al. 1999). It has 
been suggested that they are remnants of 
indurated polygonally-cracked surfaces which 
originated at the weathering front, where a 
concentration of iron and other oxides created a 
space problem, which in turn produced cracking 
and arching of some of the plates (Twidale 1982a, 
pp 315-317). 
Evidence from the southern slopes of The 
Humps sustains this interpretation for some 
components of the polygonally-cracked heavily 
indurated surface of some residual blocks have 
131 
