O ground it corresponds to the surface portion of the Earth where most human activities are carried out. It is an integrated part of the landscape, responsible for sustaining plant life and maintaining related natural resources. Above all, soil is also an important natural resource.
The soil formation process is called pedogenesis and it occurs mainly due to the action of the weathering, responsible for the wear of an original rock (mother rock) and its gradual transformation into sediments, which give rise to the material that makes up the soils.
In this sense, it is important and necessary to note that the characteristic of the soils, their time of constitution, its depth and its structure will be related to the elements acting in this process, called soil formation factors, namely: the source material, O relief, you living organisms, O climate it's the time.
a) Source material
The source material corresponds to the original rock formation that was weathered to give rise to the soils, giving it its main characteristics. As much as there are soils whose composition comes from sedimentary deposits from different areas, it is the parent rock that determines its main characteristics.
Thus, rocky materials composed of sandstones, for example, will give rise to sandy soils; material composed of granite will give rise to other types of soils. A well-known example in Brazil is the formation of the so-called “purple earth”, which comes from rocks volcanic rocks – such as basalt – which are rich in sulfur and, therefore, gave rise to a very fertile.
b) Relief
The relief – that is, the external forms of the earth's crust – is also decisive in the process of soil formation, as it directly influences the way in which the agents responsible for weathering, such as water and winds.
In areas with more sloping relief, water infiltration is less, which causes less action of the weathering on the parent rock and also a greater removal of sediments on the surface, forming soils shallower. On the other hand, in lower areas, the accumulation of water is greater, causing greater weathering action and, on the other hand, making drainage difficult, which causes a reduction in iron and more organic soils. Furthermore, the degree of slope of the relief makes it less or more exposed to sunlight, which also affects its composition and texture.
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c) living organisms
Living organisms act continuously on the soil, both in its formation and its transformation, conserving it, degrading it or altering its physicochemical composition. In this category, we can include from micro-organisms to human beings.
Microorganisms, such as bacteria, algae and fungi, act in the action of biological weathering, being present in the decomposition of rocks and also in the alteration of plant or mineralogical compounds in soils, making them more fertile or more poor. Plants act to contain the transport of sediments and animals also exert influence and impacts. In the case of human beings, the impacts are quick and often deeply felt, as in the occurrence of erosion, desertification and other processes.
d) Weather
Most weathering agents are related to meteorological and climatological processes, such as rainwater, wind and temperature. Thus, the climatic type and its variations over time are decisive for the formation of soils and also for the speed of wear of the original material.
Warmer climate regions tend to have more accelerated soil formation processes, as heat accelerates chemical relationships. The intensity and frequency of rainfall, atmospheric pressure, the annual insolation rate and the strength of the winds are also important factors in this context.
it's time
The period of time also needs to be considered in the soil formation process. Areas formed in more recent geological times were exposed to agents for less time weathered and, therefore, have younger and shallower soils, generally with less material organic. Geologically older areas, on the other hand, may have deeper soils (depending on the factors mentioned above) and, in many cases, more “washed” and chemically altered.
By Me. Rodolfo Alves Pena
