CHAPTER V 



THE PLACING OF SOIL MATERIAL (Continued) 

 III. EOLIAL OR WIND-LAID DEPOSITS 



THE statement has been made that every square mile on the 

 earth's surface has received particles from every other square mile. 

 Whether this is absolutely true or not, it shows that a very wide 

 distribution of material has been going on, and this distribution 

 has been brought about by the agency of wind. Xo place on the 

 earth's surface is free from dust. Even the snow on the great 

 continental ice sheet of Greenland contains a perceptible amount. 

 Dust storms all over the world are carrying fine material into tho 

 upper atmosphere, where it is transported for thousands of miles, 

 falling on all parts of the earth. Dust falls have occurred in which 

 a measurable amount has fallen in a few hours. In Indiana in 1895 

 a snow fall was colored brown by the large amount of dust it con- 

 tained. One sample, collected just after the storm, contained .37 

 per cent of dust by weight. The same year a sample of snow 

 collected in London contained 10.05 grains of solid material per 

 gallon of water from the melted snow. Darwin observed that the 

 water in tbe Atlantic 300 miles from the coast of northern Africa 

 was distinctly colored by the dust, and that dust was falling in the 

 ocean in perceptible quantities 1,(!00 miles from the Desert of 

 Sahara. The sirocco winds of the Sahara sometimes carry dust in 

 perceptible quantities as far north as Scotland. Professor J. A. 

 Udden 1 estimated that during an ordinary breeze a cubic mile of 

 air will contain 225 tons of dust, while in a heavy storm it will 

 contain 12(5,000 tons (Fig. -IS). The dust picked up by winds 

 together with that thrown into the atmosphere by volcanoes has 

 played an important part in the formation of soils. 



Classes of Wind-laid Material. The wind-laid deposits are 

 dunes, loess in part, adobe in part and volcanic dust. 



1. Dunes. Sand is the common constituent forming dunes, 

 but other materials sometimes compose them, (lay and silt dunes 

 are not unusual. Coffey - found clay dunes in southern Texas, 

 while silt dunes are frequently met with in areas of deep loess. 

 Many of these are found on the eastern borders of the Mississippi 



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