erosion essay

Erosion is the eating or wearing away of land features. It is caused by a variety of factors, some natural, others man-made. The consequences can be serious both for the natural world and for man himself. The natural causes are weathering, water, ice, wind and change of temperature. The changes may be very gradual, sometimes taking millions of years and dating back to the major upheavals on the planet when the earth was very young. Wind and rain driving incessantly against sandstone, formed originally by immense pressures on early sea-beds and then lifted above sea-level by volcanic eruption or the clash of land-plates, wears the stone back into sand, thus creating beaches along the sea-shore. In the case of harder rock such as granite, surfaces are worn smooth. Weathering also erodes exposed coastlines in temperate zones. Often cliffs and dunes simply disappear over perhaps a short period of two or three hundred years. The sea encroaches, and sometimes coastal villages are lost. There is written evidence of English villages having been lost under the waves.  The sea also plays its part in the erosion process. The Netherlands, facing the turbulent North Sea, have for centuries fought the battle against salt water encroachment due to erosion. Great dykes have been built to exclude the sea, and gradually the low-lying salt flats have been sweetened and fertilized for agriculture and bulb-growing. In another way, the sea also erodes rock fragments by friction due to the tides. The smooth pebbles on northern beaches are the result of their having rubbed together over millions of years. The great ice-floes attached to the poles play a conspicuous part in regulating sea levels. In general, sea levels are thought to be rising, though opinions vary as to the rate. At present, many fear what is called the 'greenhouse effect', i.e. the punching of holes in the ozone layer due.
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While the nature takes from 100 to 400 years to build one centimetre of top soil, man can and often does destroy it almost overnight by haphazard land use and improvident husbandry. Irrational methods of cultivation, deforestation, destruction of natural vegetation due to over­grazing by pasturing animals etc., accelerate denudation. Besides, failure of rains, floods, depopulation and loss of cattle caused by famine and pestilence, disturbance caused by war and interference with or change in the natural drainage system have had their deleterious effect on the soil at some time or the other. (a) Irrational Methods of Cultivation (i) Faulty method of cultivation Particularly on the steeper slopes when the virgin land is ploughed and naked soil is exposed to the rain, the loss of fertile soil is enormous. The potato cultiva­tion in the Himalayas and the Nilgiris, where the rows run straight up and down hill, causes an abnormal rapid loss of soil. (ii) Shifting cultivation It is a primitive form of soil utilization. In shifting cultivation, framers grow food only for themselves and their families. In this system of farming a patch of forest is selected. Its tree and bushes are than cut and burnt down on the ground in order to clear room for a field. The ground is then lightly ploughed and seed is sown broadcast and racked into the soil at the first fall of rain. The soil gives rise to a better yield as it is immensely fertile owing to the wood ashes and accumu­lated humus. After two or three years' crop, when the fertility of the soil is seriously reduced, the people again change their land of cultivation. Thus the essential feature of shifting cultiva­tion is the rotation of fields rather than crops. As a result more and more land are exposed to erosion. (iii) Nature of crop grown In India, as it has been noticed the dry crop producing regions (such as millet, maize.