THE PLEISTOCENE OR GLACIAL PERIOD 869 



constant or nearly constant position for a sufficiently long period, 

 a terminal moraine (called a recessional moraine) was developed. 

 The not uncommon impression that a terminal moraine is one 

 which marks the terminus of the drift, is erroneous. The word 

 terminal refers to the terminus of the ice at the time when it formed 



the moraine. 



Fluvio-glacial Deposits 



The waters arising from the melting of the ice-sheets organized 

 themselves to a greater or less extent into streams before they left 



Fig. 579. Terminal moraine topography. (Alden, U. S. Geol. Surv.) 



the ice. 1 Ultimately, the subglacial and englacial waters escaped 

 from the ice, and when this took place, the conditions of flow were 

 changed more or less suddenly, and deposits were made in several 

 classes of situations. 



1. At the edge of the ice. Where subglacial streams flowed 

 under "head," the pressure was relieved when they escaped from 

 the ice, and decrease of velocity and deposition of load were the 

 common results. In many cases, the deposits were made at the 

 edge of the ice. After the ice melted, the deposits which had 



1 The general topic of ice drainage is discussed in Glacial Geology of New 

 Jersey, p. 113 et seq., and Jour. Geol., Vol. IV, p. 950 et seq. 



