58 SOILS: PROPERTIES AND MANAGEMENT 



45. .flSolian soils. During glaciation much fine ma- 

 terial was carried miles below the front of the glaciers 

 by streams that found their sources therein. This fine 

 sediment was deposited over wide areas by the over- 

 loaded rivers. The accumulations occurred below the 

 ice front at all points, but seem to have reached their 

 greatest development in what is now the Missouri Valley. 

 There, too, the sediment seemed finest, and, coming 

 mainly from glaciated limestones, was very rich in cal- 

 cium. It is generally agreed by glacialists that a period 

 of aridity, at least as far as this particular region is con- 

 cerned, immediately followed the retreat of the ice. 

 The low rainfall of this period was accompanied by 

 strong westerly winds. These winds, active perhaps 

 through centuries, were instrumental in the picking-up 

 and distributing of this fine material over wide areas 

 of the Mississippi, Ohio, and Missouri valleys. One 

 strong argument for this^Eolian origin is that the soil is 

 found in its deepest and most characteristic development 

 along the eastern banks of the large streams. Especially 

 noticeable is the extension down the eastern side of the 

 Mississippi River almost to the Gulf of Mexico. This 

 wind-blown material, called loess, is found over wide 

 areas in the United States, in most cases covering the 

 original till mantle. It covers eastern Nebraska and 

 Kansas, southern and central Iowa and Illinois, northern 

 Missouri, and parts of Ohio and Indiana, besides a wide 

 band, as already noted, extending southward along the 

 eastern border of the Mississippi River. Due to its 

 mode of origin, its depth is always greatest near the 

 streams and gradually becomes less farther inland. In 

 places, notably along the Missouri and Mississippi rivers, 

 its accumulation has given rise to great bluffs which 



