CHAPTER V 



CLIMATIC AND GEOCHEMICAL RELATION- 

 SHIPS OF SOILS 



Although during the process of weathering the tendency 

 of all soil is toward a common composition, such a con- 

 dition is never reached, due to different kinds and varying 

 intensities of decay and disintegration. Soils lend them- 

 selves readily to a geological classification because of this 

 difference in mode of formation. Such a classification 

 really signifies a variation in composition. A difference 

 in age, a preponderance of physical agencies over chemi- 

 cal or vice versa, a difference in the transportive agencies, 

 or a variation in climatic conditions after a soil is once 

 formed, will assuredly give a different product, not only 

 chemically, but physically and biologically as well. 



51. Climatic relationships. — It is evident that climate 

 is a factor in all geochemical relationships of soils. Not 

 only does climate determine the kind of weathering and 

 its intensity, but in many ways it influences very largely 

 the characteristics of the soils of different provinces and 

 sections. Climate must be considered also in the geo- 

 logical classification of soils, since it plays such an im- 

 portant role in determining the kind and intensity of the 

 formative agents. In any scheme of grouping for the 

 systematic survey and mapping of soils, climate is the 

 very first factor to be considered. It gives three great 

 groups — tropical, subtropical, and temperate. These 

 may in turn be subdivided into arid, semiarid, and humid. 

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