Chemical or physical changes in soil minerals and organic matter represents what type of soil forming process?
Answers
Answer:
Explanation:
Soil is generally defined as the top layer of the earth's crust, formed by mineral particles, organic matter, water, air, and living organisms. It is the interface between earth, air, and water and hosts most of the biosphere [1]. Soil, however, is not merely the sum of these constituents, but a product of their interactions. Soil is an extremely complex and variable medium; a typical sample of mineral soil comprises 45% minerals, 25% water, 25% air, and 5% organic matter; however, these proportions may vary [2].
Weathering is the driving process of soil development and describes the means by which soil, rocks, and minerals are changed by physical and chemical processes into other soil components. Therefore, weathering is an integral part of soil development. Depending on the soil-forming factors in an area, weathering may proceed rapidly over a decade or slowly over millions of years. Because it develops over very long timescales, soil can be considered a nonrenewable natural resource.
Soil formation is a dynamic rather than a static process [3] while five major factors influence the kinds of soil that develop. Wherever these five factors have been the same on the landscape, the soil will be the same. However, if one or more of the factors differ, the soils will be different. The factors are [4]:
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Climate (mainly temperature and precipitation). Climate determines the nature of the weathering that occurs. Temperature and precipitation, for example, affect the rates of physical, chemical, and biological processes that define the profile development.
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Living organisms. Native vegetation, microbes, soil animals, and human beings are factors that influence organic matter accumulation, profile mixing, nutrient cycling, and soil structural stability.
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Nature of parent material. Geological processes have brought to the Earth's surface numerous parent materials in which soils form. The nature of parent materials influence mainly soil texture1 and thus many physical properties of soil such as downward movement of water, composition, natural vegetation, and the quantity and type of clay minerals present in the soil profile.
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Topography of the site, which relates to the configuration of the land surface and is described in terms of difference in elevation, slope, etc. The topography of the land can hasten or delay the processes of climate forces and therefore can modify their effects as well as the vegetative effects, having a major direct effect on soil formation and on the type of soil that forms.
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The length of time that parent material have been subjected to weathering. The time required for the development of a horizon, however, is influenced by the parent material, the climate, and the vegetation, emphasizing the interaction of time with the other soil-forming factors.
A soil is distinguished from weathered parent material by the vertical differentiation it exhibits due to biological activity, so that the properties that are singled out in most systems of soil classification must be displayed in the soil profile [5]. Soil only develops where there is a dynamic interaction between the air, water, living organisms, and geology. It is these dynamic interactions, which contribute to the multiple functions that soils perform.
Despite the above theoretical terms, there are different concepts as to what soils are, depending on the purpose for which a soil is used. For example, to a mining engineer, soil is the debris covering the rocks or minerals that must be quarried. It is, therefore, a nuisance and must be removed. To a highway engineer, soil may be the material on which a roadbed is to be placed and if its properties are unsuitable, it will need to be removed and replaced with rocks and gravels. To an average homeowner a good soil is rich, dark, and crumbly as opposed to “hard clay,” which resists being spaded into a seedbed for a flower or vegetable garden. The farmer, along with the homeowner, looks upon the soil as a habitat for plants. However, the farmer earns a living from the soil and is therefore forced to pay more attention to its characteristics. For the farmer, soil is more than useful—it is indispensable. All these different perspectives of what this medium is, have led to a misunderstanding and devaluation of soil importance for our life and made soil the poor relevant of the other two major life components, ie, water and air. One more reason for this devaluation is that although water and air degradation are fast-seen processes with obvious consequences on human health and the quality of the environment, the degradation of soil is a very slow process that may occur for many years without giving obvious consequences or with consequences that may be easily underestimated (eg, reduced fertility, need of more intense fertilization), but when at the last stage degradation is nonreversible.