WIND CORRASION 



53 



gillaceoiis rock surfaces, and separated by more or less fluted 

 ridges. (Fig. I3-) ' 



Such structures in an early stage are also found in the region 

 near Biggs, Oregon. What may be a similar structure is seen in 

 the contact of the Upper Cambric Olelius limestones with the high- 

 est bed of the Ceratopyge limestone in central Sweden, the lower 



Fig. 13. 



Diagrammatic section of yardangs of Central Asia, the deeper de- 

 pressions filled by sand. (After Sven Hedin.) 



limestone surface being grooved irregularly, sometimes for a depth 

 of a few centimeters, and the succeeding limestone filling the 

 crevices. Other eolian erosion features are seen in the Bad Land 

 , topography of western North America, the remarkable sandstone 

 pillars of the Bastei, in Saxony, the equally remarkable stone pillars 



Fig. 14. 



Erosion columns \n sandstone. 1 he result of eolian 

 Monument Park, Colorado. (After Haydtn.) 



of Tertiary sandstone, capped by harder iron-cemented layers, found 

 in Monument Park, Colorado, and the similar erosion pillars or 

 gour (singular gara) of Egypt. In part these are probably due to 

 deflation of material previously disintegrated. (Fig. 14.) 



The natural' sand-blast in the San Bernardino Pass, in southern 

 California, is so powerful that the modern telegraph poles of the 

 Southern Pacific Railway are greatly damaged and have to be pro- 



