THE PLEISTOCENE OR GLACIAL PERIOD. 



379 



they often disregard topography to the extent of crossing ridges and 

 uplands a few hundred feet in height (200 to 400 feet in Maine 1 ). 

 Kame-terraces and deltas, also, are often well above the bottoms of 

 the depressions with which they are associated. 



. 



Fig. 507. — Section of glacial drift which, though not stratified, was largely worked 

 over by water. The stones are water-worn rather than glacier-worn. North- 

 east part of Newark, N. J. (N. J. Geol. Surv.) 



Changes in Drainage Effected by Glaeiation. 



The great and unequal erosion of the ice-sheets, and especially the 

 great and unequal deposition of the drift, produced a profound effect 

 upon the topography of the planer parts of the area affected by glaeia- 

 tion. One of the conspicuous results of this alteration of the topogra- 

 phy was the derangement of the drainage. One of the results is seen 



1 Stone, Mono. XXXIV. U. S. Geol Surv., p. 434. 



