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44 FUNDAMENTALS OF PHYSICAL GEOGRAPHY in the next chapter on landforms and their Is weathering solely responsible for soil evolution. formation? If not, why? There is a shift of materials in mass movements as well as in erosion from one Pedology is soil science. A pedologist is a place to the other. So, why can’t both be treated as one and the same? Can there soil-scientist. be appreciable erosion without rocks undergoing weathering? Soil-forming Factors Five basic factors control the formation of soils: S OILF ORMATION (i) parent material; (ii) topography; (iii) climate; (iv) biological activity; (v) time. In fact soil You see plants growing in soils. You play in forming factors act in union and affect the the ground and come into contact with soil. action of one another. You touch and feel soil and soil your clothes while playing. Can you describe it? Parent Material Soil is a dynamic medium in which many chemical, physical and biological Parent material is a passive control factor in activities go on constantly. Soil is a result soil formation. Parent materials can be any in-situ or on-site weathered rock debris of decay, it is also the medium for growth. (residual soils) or transported deposits It is a changing and developing body. It has many characteristics that fluctuate with the (transported soils). Soil formation depends seasons. It may be alternatively cold and upon the texture (sizes of debris) and structure (disposition of individual grains/particles of warm or dry and moist. Biological activity debris) as well as the mineral and chemical is slowed or stopped if the soil becomes too cold or too dry. Organic matter increases composition of the rock debris/deposits. when leaves fall or grasses die. Nature and rate of weathering and depth of weatheringmantleareimportantconsiderations under parent materials. There may be Process of Soil Formation differences in soil over similar bedrock and Soil formation or pedogenesis depends first dissimilar bedrocks may have similar soils on weathering. It is this weathering mantle above them. But when soils are very young (depth of the weathered material) which is and have not matured these show strong links the basic input for soil to form. First, the with the type of parent rock. Also, in case of weathered material or transported deposits are colonised by bacteria and other inferior some limestone areas, where the weathering processes are specific and peculiar, soils will plant bodies like mosses and lichens. Also, show clear relation with the parent rock. several minor organisms may take shelter within the mantle and deposits. The dead Topography remains of organisms and plants help in humus accumulation. Minor grasses and Topography like parent materials is another passive control factor. The influence of ferns may grow; later, bushes and trees will start growing through seeds brought in by topography is felt through the amount of birds and wind. Plant roots penetrate down, exposure of a surface covered by parent burrowing animals bring up particles, mass materials to sunlight and the amount of surface and sub-surface drainage over and of material becomes porous and sponge-like with a capacity to retain water and to permit throughtheparentmaterials. Soilswillbethin on the passage of air and finally a mature soil, a steep slopes and thick over flat upland areas. complex mixture of mineral and organic Over gentle slopes where erosion is slow and products forms. percolation of water is good, soil formation is Reprint 2026-27