The Personality of India: Pre- and Proto-historic Foundation of India and Pakistan c13.s1.4

c13.s1.4

The glaciers, flow with a tremendous weight or mass and can grind and carry large masses of rock and other debris on their sides and at the tip of the tongue. This debris constitutes moraines, which survive the glacier and provide evidence of former glaciations. Outside these glacial areas and particularly in the foot-hills called 'Peri-glacial zones', the rivers which drain the uplands are also affected by these changes. During the glacial periods, a large amount of debris was brought down, but there was not sufficient water in the rivers to carry them. Hence all this additional load was deposited by the rivers in their upper courses. During the Inter-glacial periods, however, the additional water released by the melting of the ice increased the velocity of the rivers, which cut through their previous deposits leaving a portion of their former beds on the flanks, which survive as terraces. This process of building and cutting, technically called 'aggradation' and 'erosion' respectively, can be noticed by a study of the river valleys. Since the man and his contemporary animals met at this life-giving rendezvous viz. the river, the rivers tell the story of the man who lived on its banks. Since the rivers are very sensitive to the climatic changes, which directly influence the volume of water in the bed, the rivers throw light on their environment too.