Page 215 - Fundamentals of Geomorphology

198 PROCESS AND FORM

a
( ) Solution () Collapse
b

c
d
( ) Suffossion ( ) Subsidence

Salt
Salt
Plate 8.10 Collapse dolines at the watertable, Wood
Buffalo National Park, Alberta, Canada. The dolines are
created by collapses through dolostone into underlying
gypsum. The diameters are 40–100 m.
Figure 8.7 The main genetic classes of doline. (a) Solution (Photograph from Parks Canada archives)
doline. (b) Collapse doline. (c) Suffossion doline.
(d) Subsidence doline.
Source: After Ford and Williams (1989, 398)
worn down and the bottom is filled with debris.
Eventually, they may be indistinguishable from other
dolines except by excavation. The largest open col-
lapse doline is Crveno Jezero (‘Red Lake’) in Croatia,
which is 421 m deep at its lowest rim and 518 m
deep at its highest rim. If the collapse occurs into a
water-filled cave, or if the water table has risen after
the collapse occurred, the collapse doline may con-
tain a lake, often deep, covering its floor. Such lakes
are called cenotes on the Yucatán Peninsula, Mexico,
and ‘obruk’ lakes on the Turkish plateau. Some of
the cenotes near the Mayan ruins of the northern
Yucatán are very large. Dzitnup, at the Mayan ruins
of Chichén Itzá, is a vertical-walled sinkhole some
Plate 8.9 Small doline in steeply dipping limestone in the 60 m wide and 39 m deep, half-filled with water.
Rocky Mountain Front Ranges. The doline is formed on Subjacent karst-collapse dolines form even more
a cirque floor in the valley of Ptolemy Creek, Crownest dramatically than collapse dolines when beds of an
Pass, Alberta, Canada.
(Photograph by Derek C. Ford ) overlying non-calcareous rock unit fall into a cave
in the underlying limestone. An example is the Big
Hole, near Braidwood, New South Wales, Australia.
2 Collapse dolines are produced suddenly when Here, a 115-m-deep hole in Devonian quartz sand-
the roof of a cave formed by underground solu- stone is assumed to have collapsed into underlying
tion gives way and fractures or ruptures rock and Silurian limestone (Jennings 1967). As with collapse
soil (Figure 8.7b; Plate 8.10). Initially, they have dolines, subjacent karst-collapse dolines start life
steep walls, but, without further collapse, they as steep-walled and deep features but progressively
become cone-shaped or bowl-shaped as the sides are come to resemble other dolines.