Wednesday, 13 April 2016

LANDFORMS PRODUCED BY UNDERGROUND WATER :


·        Topographical features formed by underground water can be seen particularly, in an 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.





·        ‘Karst’ word comes from the Karst region of Adriatic Sea coast in Croatia (Yugosalvia) 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.
(a) Topographical features formed on the surface, like sink holes and swallow holes.
(b) Topographical features formed underground like caverns, stalactites and stalgmites.
a) Topographical features formed on the surface :
1.   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 steepsided, dugholes.
·        They develop where the limestone is more susceptible to solution, weathering or where an underground cover near the surface has collapsed.





2.   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.




b) Topographical features formed underground :

3.   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 Kotamsar in the tribal district of Bastar in Chhattisgarh are famous caverns of India.





4.   Stalactites :
·        They are the major depositional features formed in the caverns in limestone regions.
·        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.




5.   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.
·        These type of depositional features are called stalagmites.
·        As the process grows, both stalactite and stalagmite often join together to form vertical columns in the caverns.




C.SPRINGS :

 ·     Springs are surface outflow of ground water through an opening in a rock under hydraulic pressure.
·     In such cases the aquifer is either exposed at the surface or it
   underlies an impermeable rocks.
·     The amount of water in the aquifer depends upon the amount of rainfall in that area, landform characteristic and the size of the aquifer.





Hot Spring :
·     Sometimes the water that flows out of the spring is hot.
·     Such springs are called hot springs.
·     They generally occurs in areas of active or recent vulcanism.
·     In volcanic regions the underground water gets heated up by coming in contact with hot rocks or steam.
·     Hot springs are found in many parts of India, especially in the Himalaya in Jammu and Kashmir and Himachal Pradesh.
·     They also occur in Uttarakhand, Jharkhand, Haryana and Assam. Manikaran in Kulu Valley, Tatapani near Shimla, Jwalamukhi in Kangra, Sohna in Haryana, Rajgir and Sitakund in Jharkhand and Badrinath in Uttarakhand have hot springs.



D.GEYSERS :
·     Springs emitting hot water and steam in forms of fountains or jets at regular intervals are called geysers.
·     In case of a geyser, hot water is ejected violently because of the pressure created by steam.
·     The water does not come out continuously but it flows out intermittently.

·     The period between two emissions is sometimes regular. 

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