ORIGIN OF 



Wind Blown Soils. In any region where the soil becomes very 

 dry and is not covered with vegetation, as in deserts or arid 

 sections, the soil particles may be taken up by wind, and perhaps 

 carried considerable distances. The attrition of the wind-borne 

 particles reduces the softer minerals rapidly to dust, and harder 

 minerals, such as quartz, more slowly. The dust and sand are 

 separated, as the dust is carried farther. Wind-borne desert 

 sands thus consist largely of quartz. Dust carried by upward- 

 whirling winds into the higher currents of the air, is. often trans- 

 ported for hundreds of miles beyond the arid region from which 

 it is taken. In 1901 dust carried from the Sahara northward by 

 a storm, fell with rain over southern and central Europe and as 

 far north as central Germany and Denmark, causing a "black 

 rain." 



Fig. 2i. Dune sands, Lake Michigan. 



In northern China an area as large as France is deeply covered 

 with a yellow pulverulent earth called loess, but which many 

 consider a dust deposit blown from the great Mongolian desert 

 to the west of it. The soils of some of our western States are 

 wind-blown soils. 



Even in humid climates, in many places along the seashore, or 

 lake beaches, as in New Jersey or Michigan, the beach sand is 



