(a) Lapies
The leaching action of the ground water as it passes through the limestone region, produces a highly rugged topography. Where the limestone is exposed at the surface, water running across the surface gives rise to straight rounded grooves with sharper ridges in between.
These are called rillenk-arren. The ground water may enlarge the joints of the limestone into a conjugate pattern of clefts and ridges. This surface is called lapis-surface or limestone-pavement. The clefts in such a pavement are called grikes and the ridges clints.
(b) Sink
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It is a large solution cavity, may be several metres in diametre, open to the sky. These are also known as dolines, sink-holes ox swallow-holes. Sometime the sink-holes become so numerous that the sides begin to touch one another.
Surface drainage becomes limited to short sinking creeks, those that disappear in to the ground. Along such streams there are small holes where water swirls into small openings leading into caverns.
(c) Caverns
These are interconnected subterranean cavities in limestone, formed by the solution action of ground water. These cavities are always having roofs intact.
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Cavems always vary considerably in size within wide limits and are sometimes of exceptionally large dimensions and are commonly interlinked. The horizontal linking passages are known as galleries and the inclined or vertical ones as shafts.
(d) Solution Valleys
Sometimes the roof of a cavern may collapse, enlarging it in an upward direction. With continued solutions, the collapse may reach the surface and a hollow, usually elongated and narrow, may be produced and form a solution valley.
These valleys are normally developed on limestones and are also known as dry-valleys. They resemble the channels formed by running water on the surface. Many such valleys are also called blind-valleys as the water from their streams is lost to subsur face channels.
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In case of partial failure of the roof on top of a cavern, there occurs a natural bridge of limestone over-arching the solution valley. These natural bridges are, thus, the remnants of the roof of a cavern.
(e) Polje
These are large depressions, occurring mainly due to the roof collapse over great Karst chambers. They are characterized by their extensive size, flat bottom and the shape of a closed basin with steep sides. They are often filled with water forming polje lakes. Small residual hills found on the floor of poljes are called Hums or pepino-hills.
(f) Stylolite
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It is an irregular suture like boundary developed at the junction of two consecutive soluble rocks, where the less soluble portions of the consecutive beds projects into each other.