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SAI International School
                                               Subject - Chemistry

                                                      Class - VII
                                      Topic - SOIL; A Natural Resource
                      Sub-topic - Soil Erosion, Soil Pollution, Soil Conservation


                                                   Lesson Notes


               Soil Erosion:

                 The gradual removal of the top soil by the action of flowing water, wind, waves
                   and snow is called soil erosion.
                 It occurs all the time and thus causes the degradation of soil.

               Factors affecting soil erosion can be both natural as well, as man-made.


                   (i)    Floods and heavy rains loosen the soil particles.
                   (ii)   Droughts result in the depletion of vegetation making it easier for rains and
                          winds to carry away soil particles.
                   (iii)   Deforestation makes the land barren. So there are no roots to hold the soil
                          together and it gets eroded easily by rain and wind.
                   (iv)   Poor farming or incorrect irrigation methods damage the soil and lead to
                          soil erosion.
                   (v)    Overgrazing  of  animals,  development  of  housing,  construction  of  roads
                          and occurrence of forest fires are some factors that lead to soil erosion.




























               Soil Pollution:


               Contamination of soil by presence of non-desirable substances and chemicals is
               known as soil pollution.


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