Karst topography develops through the dissolution of soluble rocks, especially limestone, dolomite, and gypsum, by groundwater containing dissolved carbon dioxide. It therefore forms largely through carbonation, a type of chemical weathering. The name comes from the Karst region of Europe, historically associated with the former Yugoslavia.
Formation of Karst Topography
The notes identify the following favourable conditions:
- A thick and extensive body of soluble rock, such as limestone, dolomite, or gypsum.
- A humid or moist climate with moderate rainfall.
- Rainwater that combines with atmospheric and soil carbon dioxide to form weak carbonic acid.
- Permeable or porous material above the soluble rock.
- Numerous joints, cracks, and fractures that allow water to seep into the rock.
Moderate rainfall sustains solution: according to the notes, too little rainfall limits chemical reaction, while very heavy rainfall may remove soluble material too quickly.
Erosional Landforms
Sinking Creeks, Cracks, and Bogaz
Water percolates into well-jointed soluble rock through cracks and fractures. The initial openings through which surface water sinks are described as sinking creeks or cracks. A comparatively large solution-enlarged fissure or narrow gorge is called a bogaz.
Lapies: Pinnacles and Clints
Differential solution widens surface cracks into grooves and troughs, creating an uneven limestone pavement called lapies (also spelled lapiés or known as karren).
- The raised, resistant portions are described in the notes as pinnacles.
- The intervening blocks and fissures are referred to as clints; in standard limestone-pavement terminology, the blocks are clints and the solution-widened fissures are grikes.
Sinkhole and Swallow Hole
- Sinkhole: a rounded or funnel-shaped depression created by dissolution or collapse in soluble rock.
- Swallow hole: an opening through which a surface stream disappears underground. The notes describe it as a larger depression produced when multiple sinkholes merge, though the standard term primarily refers to the stream-sinking point.
Doline
A doline is a closed karst depression, commonly produced by solution or cave-roof collapse. The notes describe it as a large depression formed from merged sinkholes and swallow holes and also call it a collapsed sink.
Uvala
An uvala is a larger, irregular, valley-like closed depression formed by the coalescence of several dolines.
Polje
A polje is a very large, steep-sided, flat-floored closed depression in a karst region. The notes describe it as a karst valley formed when dolines and uvalas merge.
Karst Window
A karst window forms when part of the roof over an underground stream or cave collapses, exposing the underground feature at the land surface.
Cave or Cavern
A cave or cavern is a large underground chamber or passage formed mainly by the dissolution of soluble rock.
Depositional Landforms: Speleothems
Minerals carried in dripping groundwater are deposited inside caves as speleothems.
- Stalactite: a tapering mineral deposit that hangs from a cave roof as mineral-bearing water drips from the ceiling.
- Stalagmite: an upward-growing deposit on the cave floor, formed below a drip point.
- Cave pillar or column: a continuous mineral column formed when a stalactite and stalagmite grow until they join.