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GEOMORPHIC PROCESSES 43 beddingplanesthatdipsteeply.Rockfallisfree by rock debris carried by these geomorphic falling of rock blocks over any steep slope agents also aids greatly in erosion. By erosion, keeping itself away from the slope. Rock falls relief degrades, i.e., the landscape is worn occurfromthesuperficiallayersoftherockface, down. That means, though weathering aids an occurrence that distinguishes it from erosion it is not a pre-condition for erosion to rockslide which affects materials up to a take place. Weathering, mass-wasting and substantialdepth. erosion are degradational processes. It is erosion that is largely responsible for Between mass wasting and mass continuous changes that the earth’s surface movements, which term do you feel is is undergoing. As indicated in Figure 6.1, most appropriate? Why? Can solifluction denudational processes like erosion and be included under rapid flow movements? transportationarecontrolledbykinetic energy. Why it can be and can’t be? The erosion and transportation of earth materials is brought about by wind, running water, glaciers, waves and ground water. Of In our country, debris avalanches and these the first three agents are controlled by landslides occur very frequently in the Himalayas. There are many reasons for climaticconditions.Theyrepresentthree states this. One, the Himalayas are tectonically of matter —gaseous (wind), liquid (running water) and solid (glacier) respectively. active. They are mostly made up of sedimentary rocks and unconsolidated Can you compare the three climatically and semi-consolidated deposits. The slopes are very steep. Compared to the controlled agents? Himalayas, the Nilgiris bordering Tamilnadu, Karnataka, Kerala and the The work of the other two agents of Western Ghats along the west coast are erosion-waves and ground water is not relatively tectonically stable and are controlled by climate. In case of waves it is mostly made up of very hard rocks; but, the location along the interface of litho and still, debris avalanches and landslides occur though not as frequently as in the hydro sphere — coastal region — that will Himalayas, in these hills. Why? Many determine the work of waves, whereas the work of ground water is determined more by slopes are steeper with almost vertical the lithological character of the region. If the cliffs and escarpments in the Western Ghats and Nilgiris. Mechanical weathering rocks are permeable and soluble and water due to temperature changes and ranges is available only then karst topography is pronounced. They receive heavy develops. In the next chapter we shall be amounts of rainfall over short periods. dealing with the landforms produced by each So, there is almost direct rock fall quite of these agents of erosion. frequently in these places along with Deposition is a consequence of erosion. landslides and debris avalanches. The erosional agents loose their velocity and hence energy on gentler slopes and the E ROSION AND DEPOSITION materials carried by them start to settle themselves. In other words, deposition is not Erosioninvolvesacquisitionandtransportation actually the work of any agent. The coarser of rock debris. When massive rocks break materials get deposited first and finer ones into smaller fragments through weathering later. By deposition depressions get filled up. and any other process, erosional geomorphic The same erosional agents viz., running water, agents like running water, groundwater, glaciers, wind, waves and groundwater act as glaciers, wind and waves remove and aggradational or depositional agents also. transport it to other places depending upon What happens to the surface of the earth the dynamics of each of these agents. Abrasion due to erosion and deposition is elaborated Reprint 2026-27