Karst window. Sometimes the sink holes collapse and form a broad and open area. Such broad and open area formed by the collapse of a sink-hole is called Karst-window.
Uvala. Adjacent dolines coalesce into bigger holes which are known as Uvalas. They are formed by endogenetic forces. Subsidence and faulting are the main causes of their origin. Uvalas have vertical walls, closed basin and an oval (egg like) shape. Alluvial soil is found spread over it. The inlets which bring water are pipe like and are known as Ponore. Some ponores act as inlets and some as out-lets of water.
Sinking Creeks. Rivers flowing in a limestone region are dried within its basin. It is due to deep faults lying in its course. These faults draw the water from the rivers and supply the underground areas with it. These faults are known as sinking creeks. They usually originate in the form of a hole. When these faults are opened on the roots, they are known as Bogas.
Polge and Blind Valley. Many uvalas coalese into a Polge. If polges are formed by erosion, they are called Blind Valleys by Davis. A lake is usually found to exist in the centre of a polge. Adriatic coast and Jamaica have a large number of polges. Ponores are found in polges.
Pocket valley. The coral rocks at some places are so much permeable that the water percolates from the steep sloped mouth of the base of the river. Many depressions are formed which have wall-like sides and plain floors. When the solution process widens and broadens them, they are known as Pocket valleys. There is a difference between pocket valleys and blind valleys. In pocket valleys the water table is so high that it comes out in the form of springs. On the other hand the water in the blind valleys percolates away from them into underground channels.
Dry Hanging Valleys. The rivers which flow over non-limestone areas and enter a limestone region usually erode into deep courses. This lowers the water table in the area. The tributaries of such a river which originate in a limestone region do not have much water. Their water escapes through sink-holes into subterranean courses. Due to lowering of water-table, the water of the rivers percolates fast into underground areas. Such rivers appear dry and are known as Dry valleys or Bournes. Such dry tributaries appear hanging over the main valley and are called dry Hanging Valley.
Hums. When limestone rocks situated over an impermeable rocks layer are eroded away by solution, their last remnants are called Hums. Sometimes monad-knocks in karst region are also called Hums.
Terra Rossa. When the water percolates in an area, many components of soil are dissolved away. This brings about a change in the chemical composition of the soil. Usually red soil is produced due to this process. The layers of such a soil are thick at some places while they are thin at other places. Such a soil covers the area with it. It is known as Terra Rossa.
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