. Soil physics and management. areas (Fig. 42), and ice movement started from these inpractically all directions, but probably not from all centers at thesame time, or at least not to the same extent. Smaller centers of ac- 46 SOIL PHYSICS AND MANAGEMENT cumulation existed in the Kooky and Sierra Nevada Mountains andon the Island of ISIewfoundland. In Europe (Fig. 43) the Scandina-vian was the i^rincipal and the Ural, a secondary center. The glaciersof the Alps and Caucasus were much more extensive than at present,(a) The Jerseyan or Nebraskan Glaciation and AfIonianInterglacial Stage.—The fir
. Soil physics and management. areas (Fig. 42), and ice movement started from these inpractically all directions, but probably not from all centers at thesame time, or at least not to the same extent. Smaller centers of ac- 46 SOIL PHYSICS AND MANAGEMENT cumulation existed in the Kooky and Sierra Nevada Mountains andon the Island of ISIewfoundland. In Europe (Fig. 43) the Scandina-vian was the i^rincipal and the Ural, a secondary center. The glaciersof the Alps and Caucasus were much more extensive than at present,(a) The Jerseyan or Nebraskan Glaciation and AfIonianInterglacial Stage.—The first glacial advance probably came fromthe Keewatin center and is called the Jerseyan or the Nebraskan,because small areas of surface deposits made by this glacier arefound in those states. All other deposits of this advance have beenburied by subsequent ice sheets and it is difficult to make a carefulstudy of them because of superposed material. There is no evidencethat the area between New Jersey and Nebraska was covered by. Fig. 41.—Map showing extent and southern limit of glaciation in North Lakes Agassiz, Lahonton and Bonne\ilIe. (Compiled from several sources.) this ice sheet. This glacier receded and the drift deposited by itbecame eroded, weathered and the surface was changed into peat beds were formed in undrained areas. Tliis inter-glacial stage is knoT\Ti as the Aftonian. (b) The Kansan Glaciation and Yarmouth InterglacialStage.—The second glacial advance Avas from the Keewatin centeralso, and extended into Iowa, Illinois, Nebraska, and Kansas, andderived its name from the exposure of drift in the latter the ice receded soil was formed from the siirface of the drift GLACIAL OR ICE-LAID DEPOSITS 47 and organic matter accumulated as peat in some swampy stage is known as the Yarmouth. (c) The Illinoisan Glaciation and Sangamon InterglacialStage.—The third glacial advance was from the La1:)
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