EOLIAL OR WIND-LAID DEPOSITS 



65 



Chemical Analyses of Loess from Various Sources * 



* Contains H of organic matter. 

 t Organic matter dried at 100 C. 

 t Ignition. 



3. Adobe. Adobe is a calcareous clay of a gray, gray-brown 

 or dull yellowish color, very fine grained and porous, friable and yet 

 standing in vertical escarpments for many years. The adobe soils 

 are found in the arid and semi-arid regions and represent both wind 

 and water deposits. Much of the adobe was undoubtedly formed in 

 shallow lakes by the deposition of very fine material which con- 

 tained a large amount of carbonate, resembling loess in this respect. 

 Professor Russell r> speaks of this deposit as assorted and spread out 

 over the valley bottom by the action of ephemeral streams where it 

 becomes mixed with dust blown by the winds from the neighboring 

 mountains and rendered more or less coherent by the cementing 

 action of carbonate of lime. It occurs from Mexico northward to 

 Oregon and Idaho and from California to Colorado. In altitude it 

 varies from sea level in Arizona to 8,000 feet and in thickness from 

 a few feet to 3,000 feet or more. 



4. Volcanic Dust. During the explosive eruptions of vol- 

 canoes large quantities of dust and ashes are thrown into the air 

 which may be carried long distances by the wind. Volcanoes 

 existed formerly where no active ones are found at present. Xorth- 

 western United States was a region of great volcanic activity in 



