Landforms Produced by Underground Water Part – 4

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Landforms Produced by Underground Water

Underground water is also an agent of gradation like surface water. It also does the work of erosion, transportation and deposition, which results in formation of a number of picturesque topographical features. Topographical features formed by underground water can be seen particularly, in a highland composed of limestone on a large scale.

This distinctive topography formed due to the action of underground water in limestone region is known as Karst topography. The word ‘Karst’ comes from the Karst region of Adriatic Sea coast in Croatia (Yugoslavia) where such formations are noticeable. This region is made up of limestone rocks, where underground water is the most active agent of gradation.

The topographical features created by the work of underground water on limestone are of two types:

  1. Topographical features formed on the surface, like sink holes and swallow holes.

  2. Topographical features formed underground like caverns, stalactites and stalagmites.

Sink Holes: A sinkhole is a surface depression in a region of limestone or chalk terrain. Some sinkholes are filled with soil washed from nearby hillsides, while others are steep sided, dug holes. They develop where the limestone is more susceptible to solution, weathering or where an underground cover near the surface has collapsed.

Swallow Holes: They are cylindrical in shape lying underneath the sinkholes at some depth. In limestone regions, the surface streams often enter the sinkholes and then disappear underground through swallow holes. It is so, because these holes are connected to the underground caverns on their other side.

Karst Landform Features

Karst Landform Features

Karst Landform Features

Caverns: Caverns are interconnected subterranean cavities in bedrock formed by the corrosions action of circulating underground water on limestone. They are found near Dehradun in Uttarakhand, and in Almora in Kumaon Himalayas. The caves of Kotumsar in the tribal district of Bastar in Chhattisgarh are famous caverns of India.

Stalactites and Stalagmites: The water containing limestone in solution seeps through the roofs of the caverns in the form of a continuous chain of drops. A portion of the water dropping from the ceiling gets evaporated and a small deposit of limestone is left behind on the roof. This process continues and deposit of limestone grows downwards like pillars. These beautiful forms are called stalactites.

Stalactites and Stalagmites

Stalactites and Stalagmites

Stalactites and Stalagmites

When the remain in portion of the water dropping from the roof of the cavern falls on the floor, a part of it is again evaporated and a small deposit of limestone is left behind. This deposit grows upward from the floor of the cavern. This type of depositional features is called stalagmites. As the process grows, both stalactite and stalagmite often join together to form vertical columns in the caverns.

In Brief, It Can Be Said That:

Among the agents of gradation, the running water is most effective and important. A river has three-fold action- erosion, transportation and deposition. The ability of a river to move rock material depends upon- the speed of water, the volume of water, the land structure, and the size, shape and weight of load. The work of river erosion is accomplished in four different ways-corrasion, corrosion, hydraulic action, and attrition. The river transports its load in four different ways- by traction, saltation, suspension and solution. The deposition starts in plains and low-lying areas.

The whole path followed by a river is called its course. The course of a river is divided into three sections- the upper course, the middle course, and the lower course. The upper course lies in the mountains where vertical cutting is more important. The landforms features produced are gorges, canyons, rapids, waterfalls. The middle course lies at the junction of mountain and plains. The work of river is mainly transportation with some deposition. The land feature produced is meander. The lower course lies in the plain area. Here the work of river is mainly deposition. The land features produced are ox-bow lakes, braided streams, alluvial and flood plains, delta, and estuary.

The water which percolates inside the earth is called underground water. The upper limit of underground water is called water-table. The level of water table is not uniform but it varies seasonally. Consequently, the water-table is of two types permanent water table and temporary water table. Underground water comes to the surface through wells, tube wells and springs. Wells and tube wells are manmade holes dug into the earth surface through which water is obtained. In addition to these ordinary wells, there is a special type of well in which water flows out automatically under hydraulic pressure.

They are called artesian wells. Surface outpour of ground water that from rock opening under its own pressure is called a spring. Sometimes the water flows out of springs is hot, such springs are called hot springs. When the hot springs emits water in the form of a fountain, they are called geysers.

Underground water does the work of erosion, transportation and deposition which result in number of topographical features. The major depositional features made by underground water are stalactites and stalagmites, which develop in the caverns.