Page 220 - Fundamentals of Geomorphology

KARST LANDSCAPES 203

()
a
Altitude
(m)
Normal streamsink
Partly vegetated channel
1,250 taking flood water Perennial watercourse
Half-blind valley
1,228 m 1,224 m
1,225
Stream in swamp
0 100 m
1,200
()
b
1,075
Plateau surface
Doline Doline Blind valley Stream in
1,050 swamp
The Bath
The Bath
House contact
House
1,025 position
Cave
Cave limestone–
Approx. porphyry
1,000 of
0 100 m
975
Figure 8.11 Blind and half-blind valleys in New South Wales, Australia. (a) A half-blind valley on Cooleman Plain.
(b) A blind valley at Yarrangobilly.
Source: Adapted from Jennings (1971, 110, 111)

a craggy dry valley in which the stream fed by Malham diverted the drainage underground. The ‘hanging val-
Tarn formerly flowed over the limestone to cascade over leys’, which are reported in many karst areas, resulted
the 75-m cliff of Malham Cove (Figure 8.12; Colour from the main valleys’ continuing to incise after their
Plate 4). tributaries ceased to have surface flow.
Extensive dry valley networks occur in some areas
of karst. An impressive set is found in the White Meander caves
Peak, England. Here, a few major streams – the Rivers
Manifold, Dove, and Wye – flow across the region, but Meander caves are formed where the outer bend of a
most other valleys are dry (Figure 8.13). Many of the meander undercuts a valley-side. Now, stream debris does
dry valleys start as shallow, bowl-like basins that develop not hamper rivers from lateral erosion in karst landscapes
into rock-walled valleys and gorges. Other, smaller dry as it does rivers on other rocks, because rivers carrying
valleys hang above the major dry valleys and the perma- a large clastic load cannot move laterally by corrasion
nent river valleys.The origin of such networks is puzzling as easily as rivers bearing a small clastic load can by
but appears to be the legacy of a former cover of impervi- corrosion. For this reason, meander caves are better devel-
ous shales (Warwick 1964). Once the impervious cover oped in karst terrain than elsewhere. A prime example is
was removed by erosion, the rivers cut into the limestone Verandah Cave, Borenore, New South Wales, Australia
beneath until solution exploited planes of weakness and (Figure 8.14).