(a) Explain briefly four factors of soil formation. (b) List four chemical processes in the weathering of rocks.
Explanation
(a) Factors of soil formation are: (1) parent material (2) climate (3) organisms (4) topography (5) time.
(1)Parent materials: (i) constitute the major material from which soil is formed. (ii) they are igneous, sedimentary and meta-morphic rocks. (iii) That determine the chemical composition of the soil that is formed. (iv) They also contain different minerals which account for differences in the fertility of soils formed from each of the different types. (v) determine the physical characteristic of the soil. (vi) hardness of parent material affects the rate of soil formation.
(2) Climate: (1) The two main elements of climate which affect soil formation are rainfall and temperature. (ii) rainfall affects soil formation through erosion, solution, chemical reactions and enhancement of vegetative growth whose roots cause further breakdown of rocks. (iii) temperature affects the rate of chemical weathering of rocks; (iv) temperature also causes the expansion and contraction of rocks leading to disintegration. (v) wind blast also causes abrassion of rocks. (vi) rain water transports rock particles after disintegration.
(3) Organisms: (i) organism produces CO which forms carbonic acid with water and enhances the weathering of rocks. (ii) these include microbes such as bacteria and macrobes such as earthworms. (iii) macrobes help in weathering by burrowing and creating crevices and turning or mixing soil particles. (iv) macrobes also improve soil aeration and water percolation which will enhance chemical and physical weathering. (v) microbes help in the decomposition of organic matter in the soil. (vi) they increases soil fertility. (vii) activities of man, animals and micro-organism influence the development of soil.
(4) Topography: (i) affects the rate of run-off and erosion. (ii) steep slopes encourage erosion and retard soil formation. (iii) soil formation is faster in the valley than on slopes. (iv) steepness of the slope affects the rate of abrassion of rocks and hence, soil formation.
(5) Time: (i) is very important in soil formation. (ii) a long period of time allows for the formation of matured soils (iii) a short time results in the formation of immature soils. (iv) It determines whether the soil is well developed or not. (b) Chemical processes in the weathering of rocks include: (i) hydrolysis (ii) hydration (iii) carbonation (iv) oxidation or reduction. (v) solutiorn