organic acids, give rise to formation of complex with sesquioxide ions and transfer them to subsoil from the upper horizon and little amount inside the ground water. Elimination of iron out of ferromagnesian minerals is increased owing to this activity. The overall process of weathering as reported by Jackson and Hseung in the year 1952 [16] was influenced because of elimination of iron oxides from horizon A and accumulation in horizon B. As per Vagelor et al., in the year 1933 [102–104], and Mohr et al., in the year 1944 [96], it was reported that in tropical areas vegetal canopy is highly significant. According to Mohr et al., in the year 1944, it was reported that air temperature above the soil is considerably less in case of canopy forest. Similarly, soil enveloped by forest has 10°C to 15°C. The decrease in the temperature makes all the chemical reaction slower. Organic matter decomposition is slower, causing deposition of organic substances either in or at horizon surface. The condition in deciduous tropical forest and evergreen tropical forest is considerably different. Gupta and Griffith et al., in the year 1947 [105], reported that when teak is planted in laterite soil then a crust of laterite is formed due to the soil dehydration during the dormant leafless stage or drought period. The laterite soil formed hampers the tree growth. Sherman et al., in the year 1953 [106], verified these findings in case of Hawaiian Islands.
2.3.2.5 Reduction and Oxidation Factor
Reduction and oxidation reaction influences the process of chemical weathering. As per Jackson et al. in the year 1948 [37], in equation of weathering, positive sign is assigned to oxidation. Hence, iron occurrence in ferrous state or reduction favoring conditions enabled the formation of montmorin in the intermediate stage of weathering as per Wendricks and Ross in the year 1945 [107]. Moreover, occurrence of iron in ferric state or oxidation favoring conditions favored free oxides and kaolin formation in higher weathering stage. According to Marshall and Humbert et al., in the year 1943 [13], oxidation role in weathering was reported as ferric oxide formation in quartz grains cracks which breaks the quartz crystal. Oxidation rate also has an impact on the accumulated organic matter prevailing in soil which ultimately influences the rate of chemical weathering.
2.3.2.6 Influence of Time on the Rate of Chemical Weathering
According Jackson et al., in the year 1948 [37], it was reported that for a particular particle size range and mineral species, the stages of weathering of the colloid weathering are the result of time duration of weathering and intensity function multiplication. Thorp et al., in the year 1944 [108], reported that soils present in some of the mountain displayed considerable development of soil and weathering after a particular duration of time. Retzer et al., in the year 1949 [63], reported great significance of the age of the mineral weathering and formation of dense, unique subsoils which are oftenly highly thick in case of Rocky Mountains of Central Colorado. The time of exposure or age exhibits crucial part for determining the type of mineral existing at a particular time in tropical soils. Mohr et al., in the year 1944 [96], reported five stages of weathering for the development of tropical soils. The stages include the following:
Beginning stage (unweathered virgin material)
Juvenile stage (point where there is beginning of weathering)
Virile stage (in this stage, the weathering is in highly advanced stage where the percentage of unweathered material is negligible)
Senile stage (at this point, there is completion of unweathered material weathering)
Final or end stage (at this point, development has reached to completion and the soil has been weathered.)
The above proposal displays that the weathering of mineral which contributes in formation of soil remains in equilibrium (dynamic) with the factors prevailing in the environment. According to the above proposal, at the final stage, there is the establishment of static equilibrium.
2.4 Conclusion
In this chapter, a brief summarization of process of chemical weathering and various factors like specific surface area, oxidation and reduction, biotic process, temperature, time, acidity, leaching, effect of water, etc., responsible for controlling the rate of chemical weathering is discussed.
References
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