(i) Incised meanders are formed during the youth stage of a river. With the passage of time, as the mountains and plateaus rise the meandering course starts vertical erosion and incised meanders are formed.
Meanders in plains of alluvium indicate formation during mature and old stage of the rivers.
(ii) The surface run off simply goes down shallow and sink holes and flow as underground streams and re-emerge at a distance downstream through a cave opening. When sink holes and dolines join together because of slumping of materials along their margins or due to roof collapse of caves, long narrow to wide trenches called valley sinks or Uvalas form.
(iii) Underground flow of water is more common than surface run-off in limestone areas because limestone is rich in calcium carbonate, the surface water as well as groundwater through the chemical process of solution and precipitation deposition, develop varieties of landform. These two processes of solution and precipitation are active in limestone occurring either exclusively or interbedded with rocks.
(iv) Glacier valleys show up many linear depositional forms. They are as follows:-
• Moraines- They are long ridges of glacial till. Terminal moraines are long ridges deposited at the end of the glaciers. Lateral moraines form along the sides parallel to the glacier valleys. Deposits varying greatly in thickness and in surface topography are called ground moraines.
• Eskers- It is a long winding ridge of a stratified sand or gravel found in glacier regions.
• Outwash Plains- The plains at the foot of the glacial mountains or beyond the limits of continental ice sheets.
• Drumlins- form beneath heavily loaded ice through fissures n the glacier.
(v) Wind is the primary agent for erosional features in deserts. It involves the lifting and removal of dust and smaller particles from the surface of the rocks. The wind creates a number of erosional and depositional features in the deserts.
Along with wind, running water or sheet erosion are also common in deserts.
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