46 



SOIL PHYSICS AND MANAGEMENT 



cumulation existed in the Rocky and Sierra Nevada Mountains and 

 on the Island of Newfoundland. In Europe (Fig. 43) the Scandina- 

 vian was the principal and the Ural, a secondary center. The glaciers 

 of the Alps and Caucasus were much more extensive than at present, 

 (a) The Jerseyan or Nebraskan Glaciation and Aftonian 

 Interglacial Stage. The first glacial advance probably came from 

 the Keewatin center and is called the Jerseyan or the Nebraskan, 

 because small areas of surface deposits made by this glacier are 

 found in those states. All other deposits of this advance have been 

 buried by subsequent ice sheets and it is difficult to make a careful 

 study of them because of superposed material. There is no evidence 

 that the area between New Jersey and Nebraska was covered by 



Fio. 41. Map showing extent and southern limit of glaciation in North America. 

 Also Lakes Agassiz, Lahonton and Bonneville. (Compiled from several sources.) 



this ice sheet. This glacier receded and the drift deposited by it 

 became eroded, weathered and the surface was changed into soil. 

 Even peat beds were formed in undrained areas. This inter- 

 glacial stage is known as the Aftonian. 



(b) The Kansan Glaciation and Yarmouth Interglacial 

 Stage. The second glacial advance was from the Keewatin center 

 also, and extended into Iowa, Illinois, Nebraska, and Kansas, and 

 derived its name from the exposure of drift in the latter . state. 

 After the ice receded soil was formed from the surface of the drift 



