Geology Reference
In-Depth Information
Table 8.1 Karst and pseudokarst
Formed in
Formative processes
Examples
Karst
Limestone, dolomite, and other
carbonate rocks
Bicarbonate solution
Poole's Cavern, Buxton, England;
Mammoth Cave, USA
Evaporites (gypsum, halite,
anhydrite)
Dissolution
Mearat Malham, Mt Sedom, Israel
Silicate rocks (e.g. sandstone,
quartzites, basalt, granite,
laterite)
Silicate solution
Kukenan Tepui, Venezuela; Phu Hin Rong
Kla National Park, Thailand; Mawenge
Mwena, Zimbabwe
Pseudokarst
Basalts
Evacuation of molten rock
Kazumura Cave, Hawaii
Ice
Evacuation of meltwater
Glacier caves, e.g. Paradise Ice Caves,
USA
Soil, especially duplex profiles
Dissolution and granular
disintegration
Soil pipes, e.g. Yulirenji Cave,
Arnhemland, Australia
Most rocks, especially bedded
and foliated ones
Hydraulic plucking, some
exsudation (weathering by
expansion on gypsum and
halite crystallization)
Sea caves, e.g. Fingal's Cave, Isle of
Staffa, Scotland
Most rocks
Tectonic movements
Fault fissures, e.g. Dan y Ogof, Wales;
Onesquethaw Cave, USA
Sandstones
Granular disintegration and
wind transport
Rock shelters, e.g. Ubiri Rock, Kakadu,
Australia
Many rocks, especially with
granular lithologies
Granular disintegration
aided by seepage moisture
Tafoni, rock shelters, and boulder caves,
e.g. Greenhorn Caves, USA
Source:
Partly after Gillieson (1996, 2)
in karst landscapes, but it may be subordinate to other
geomorphic processes. Various terms are added to karst
to signify the chief formative processes in particular
areas.
True karst
denotes karst in which solutional pro-
cesses dominate. The term holokarst is sometimes used
to signify areas, such as parts of southern China and
Indonesia, where karst processes create almost all land-
forms.
Fluviokarst
is karst in which solution and stream
action operate together on at least equal terms, and is
common in Western and Central Europe and in the mid-
western United States, where the dissection of limestone
blocks by rivers favours the formation of caves and true
karst in interfluves.
Glaciokarst
is karst in which glacial
and karst processes work in tandem, and is common in
ice-scoured surfaces in Canada, and in the calcareous
High Alps and Pyrenees of Europe. Finally,
thermokarst
is irregular terrain produced by the thawing of ground
ice in periglacial environments and is not strictly karst
or pseudokarst at all, but its topography is superficially
similar to karst topography (see p. 284).
Karst drainage systems are a key to understanding
many karst features (Figure 8.4). From a hydrological
standpoint, karst is divided into the surface and near-
surface zones, or epikarst, and the subsurface zones,
or endokarst.
Epikarst
comprises the surface and soil
(cutaneous zone), and the regolith and enlarged fissures
(subcutaneous zone).
Endokarst
is similarly divided into
two parts: the vadose zone of unsaturated water flow and
the phreatic zone of saturated water flow. In the upper
portion of the vadose zone, threads of water in the sub-
cutaneous zone combine to form percolation streams,
and this region is often called the percolation zone.
