Page 218 - Fundamentals of Geomorphology

KARST LANDSCAPES 201

a
() Tropical cockpits

b
() Topographic
divide

60 100
Plate 8.11 Limestone cone karst near Anxhun, Guizhou 60 80 80 60
Province, China.
30 40
(Photograph by Derek C. Ford )
Cockpit
C
ockpit
100
100
80
enough to interfere with each other and have destroyed 60
the original land surface. Such landscapes are called cone
karst (Kegelkarst in German) and are dominated by 80
projecting residual relief rather than by closed depres- 60 100 m
sions (Plate 8.11). The outcome is a polygonal pattern of
ridges surrounding individual dolines. The intensity of Figure 8.10 Tropical dolines (cockpits). (a) Block diagram.
the karstification process in the humid tropics is partly (b) Plan view.
a result of high runoff rates and partly a result of thick Source: Adapted from Williams (1969)
soil and vegetation cover promoting high amounts of soil
carbon dioxide.
Two types of cone karst are recognized – cockpit
karst and tower karst – although they grade into one
another and there are other forms that conform to
neither. Cockpits are tropical dolines (Figure 8.10). In
cockpit karst, the residual hills are half-spheres, called
Kugelkarst in German, and the closed depressions, shaped
likestarfish,arecalledcockpits,thenamegiventothemin
Jamaica owing to their resembling cock-fighting arenas.
In tower karst (Turmkarst in German), the residual
hills are towers or mogotes (also called haystack hills),
standing 100 m or more tall, with extremely steep to
overhanging lower slopes (Plate 8.12). They sit in broad
alluvial plains that contain flat-floored, swampy depres-
sions. The residual hills may have extraordinarily sharp
edges and form pinnacle karst (p. 195).
Studies in the Mackenzie Mountains, north-west Plate 8.12 Tower karst on the south bank of the Li River
Canada, have shattered the notion that cone karst, and near Guilin, Guangxi Province, China.
especially tower karst, is a tropical landform (Brook and (Photograph by Derek C. Ford )