90 GEOLOGY 



influence felt in the historic red sunsets which it occasioned. 1 It 

 is probable that dust from this eruption found its way to nearly 

 all parts of the earth. 



Volcanic dust is shot into the atmosphere rather than picked 

 up by it. Dust picked up by the win,d is perhaps transported not 

 less widely than volcanic dust, but, after settling, its point of origin 

 is less readily determined. It would perhaps be an exaggeration 

 to say that every square mile of land surface contains particles 



Fig. 52. Vertical face of loess near Huang-tu-Chai in northern Shan-si. 

 (Willis, Carnegie Institution.) 



of dust brought to it by the wind from every other square mile, 

 but such a statement would probably involve much less exaggera- 

 tion than might at first be supposed. 



Extensive deposits of dust blown about by the wind are known. 

 Considerable beds of volcanic dust, locally as much as 30 feet 

 thick, are known in various parts of Kansas and Nebraska, hun- 

 dreds of miles from the nearest known volcanic vents. In China 

 there is an extensive earthy formation, the loess (Fig. 52), some- 

 times reaching a thickness of hundreds of feet, which Baron von 

 Richtofen believed to have been deposited by the wind. 2 This 



1 A brief account of the influence of the dust on sunsets is found in Davis'a 

 Elementary Meteorology, pp. 85 and 119. 



2 Von Richtofen; "China." 



