Revision:Karst Landscapes

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Karst landscapes

Limestone

• Limestone is permeable rock but not porous.

• It is soluble in rain water, so rainwater dissolves it.

• It is a well fissured and jointed rock, as a result rainwater and surface streams and water dissolve and widen the cracks and joints.

The streams go underground, widening the joints and forming underground passageways and tunnels. Sometimes these tunnels are widened to form vast caverns, with underground lakes, streams and vast cave systems. As a result there is an absence of surface drainage in limestone areas. There are few surface streams. Streams disappear down swallow holes and reappear as springs sometimes miles away. This is called INTERMITTENT DRAINAGE.

• Soils in limestone regions are thing and infertile, often just a dry springy turf.

The thin soils and lack of surface water means an absence of trees. The grass is dry, short and wiry.

• Limestone often forms a fairly level but undulating plateau surface with steep scarp slope.

• Much bare rock shows through the thin turf.

• Limestone regions usually give a rather barren appearance.

Limestone features

LIMESTONE PAVEMENT: when the bare limestone shows through on a level surface. The cracks and joints have been widened by solution to form clints and grykes.

LIMESTONE SCAR: when the bare rock shows through on a scarp slope.

SWALLOW HOLE: the point where a stream goes underground.

DRY VALLEY: a valley that formerly had a stream in it but the stream has gone underground at a higher point.

CAVERN: when an underground tunnel has been enlarged to form a huge cave.

GORGE: formed by the collapse of a cavern.

STALACTITE: an icicle of limestone hanging from the roof of a cave or cavern formed by the constant drip of water from the roof leaving minute particles of limestone behind which gradually form a solid limestone icicle.

STALAGMITE: a pillar of limestone rising from the floor of a cave where a drip has constantly landed from the roof above.

Value of limestone regions

• Soils are too thin for areas to be of much agricultural value except as grazing for sheep.

• Limestone provides reasonable building stone.

• Raw material for cement

• Limestone is used as a flux in the steel industry, raw material in the chemical industry and for making fertiliser.

• Recreation e.g. caving and hill walking.