Named for their origin. Soils, as we have seen, may be 

 divided into residual and drift soils, depending upon whether 

 they have originated from the underlying rocks or have been 

 transported from distant regions by water and other agencies. 



FIG. 10. Vegetation invading a shallow lake 



It is possible, also, to name the soils from the agencies most 

 active in forming them, and the principal groups thus natu- 

 rally break up into smaller divisions. The residual soils may be 

 divided into the true sedimentary and the lacustrine, while drift 

 soils include the aeolian, volcanic, colluvial, glacial, and alluvial. 



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