Geology Reference
In-Depth Information
()
a
Tropical cockpits
Topographic
divide
()
b
Plate 8.11
Limestone cone karst near Anxhun, Guizhou
Province, China.
(
Photograph by Derek C. Ford
)
30
Cockpit
enough to interfere with each other and have destroyed
the original land surface. Such landscapes are called
cone
karst
(
Kegelkarst
in German) and are dominated by
projecting residual relief rather than by closed depres-
sions (Plate 8.11). The outcome is a polygonal pattern of
ridges surrounding individual dolines. The intensity of
the karstification process in the humid tropics is partly
a result of high runoff rates and partly a result of thick
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
like starfish, are called cockpits, the name given to them in
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
Canada, have shattered the notion that cone karst, and
especially tower karst, is a tropical landform (Brook and
100 m
Figure 8.10
Tropical dolines (cockpits). (a) Block diagram.
(b) Plan view.
Source:
Adapted from Williams (1969)
Plate 8.12
Tower karst on the south bank of the Li River
near Guilin, Guangxi Province, China.
(
Photograph by Derek C. Ford
)
