250 THE ILLINOIS GLACIAL LOBE. 



Meridian westward to northern Bureau County, there are numerous sand 

 knolls and ridges, 10 to 40 feet in height, which add greatly to the inequal- 

 ities i >f the surface. These sand accumulations follow the lines of ridges or 

 knolls in the moraine, rather than the depressions between them. The sand 

 is still subject to slight modification by wind action, and its ridges, as well 

 as its presence on the moraine, are probably the result of wind transportation 

 from the Green River Basin, which borders this portion of the moraine on 

 the west. 



The inner belt of this system, as noted above, is merged with the outer 

 from the vicinity of Shabbona southwestward to Pawpaw, and presents a 

 knob-and-basin topography along the line of junction. Upon separating 

 from the outer belt the topography changes to gentle undulations, and 

 there is also a tendency to ridging in the line of the belt. In places a cross 

 section would lead over at least three nearly parallel ridges separated by 

 narrow sags, the whole series occupying a width of scarcely 2 miles. The 

 ridges are, however, not distinctly maintained for long distances, but are at 

 intervals crowded together. These ridges are of about equal heig'ht and 

 rise only 25 to 50 feet above the plain on their outer border. The relief 

 on the inner or southeast border is nearly 150 feet in eastern Lee County, 

 and this great relief is maintained for 10 or 12 miles southwestward in south- 

 eastern Lee and northwestern Lasalle counties. Upon entering Bureau 

 County the relief decreases rapidly, as already noted, but the expression 

 continues as strong as in the portion having greater relief. Knolls 20 feet 

 or more in height are closely aggregated, and are disposed in chains trending 

 in line with the belt. Upon approaching the Illinois Valley they become 

 more scattering, and the belt fades out about 2 miles north of Depue. The 

 feeblv developed portion of this belt is shown in the northwest corner of 

 the Lasalle topographic sheet and in the eastern part of the Hennepin 

 sheet between East Bureau and Brush creeks. The ridge which leads south- 

 ward from Earlville past Utica, a few miles east of this moraine, is discussed 

 farther on, as is also the topography in the line of continuation of this moraine 

 in Putnam, Marshall, Woodford, and McLean counties. (See pp. 261, 281.) 



In Bureau, Marshall, and Peoria counties Tll6 tllil'd SeCtioil of tile BloOmingtOll 



morainic system embraces the portion of the moraine west of the Illinois 

 River in Bureau, Marshall, and Peoria counties. This consists mainly of 

 a large ridge, -4 to 6 miles in width and 100 feet or more in height above 



