152 NEW YORK STATE MUSEUM 



CJmpter 5 



RETREAT OF THE ICE SHEET IN THE OHAMPLAIN 



VALLEY 



The retreat of the ice sheet in the Champlain valley has been 

 largely obscured by the extensive modification of deposits at 

 low levels through the action of waves and running water. In 

 only one portion of the field was much attention paid in the 

 course of the present investigation to the ice retreat and at no 

 point in the length of the lake am I at present able to state the 

 precise line of ice frontage across the lake valley. The follow- 

 ing notes on such localities as chanced to be examined in the 

 course of the search for water levels by no means give a com- 

 plete account of the recession. 



As will be noted from allusions in these descriptions and from 

 the conclusions to which I have been led, a glacial lake appears 

 to have extended northward in the valley pari passu with the 

 retreat of the ice front. Still earlier as remarked by several 

 observers there were probably lakes held in along the margin of 

 tlie ice sheet both on the Adirondack and Green mountain sides. 

 Taylor has given the name of Lake Adirondack to such a body 

 of water whose traces he recognized in the region back of Platts- 

 burg. Probably other similar lakes existed in the upper basins 

 of the Winooski and Lamoille rivers in Vermont [see pi. 27]. 

 Some or all of these marginal lakes must have later become con- 

 fluent with or drained into the greater lake which was held in 

 by the ice sheet while its front stretched across the valley from 

 the Green mountains to the Adirondacks. 



Mr Baldwin has supposed this front to have been concave 

 northward on account of the melting effect of the water which 

 bathed it. This need not necessarily have been the case, how- 

 ever, provided the rate of the forward movement during the 

 retreat counterbalanced or exceeded at times the rate of melt- 

 ing. My studies on the Mooers quadrangle have led me to an 

 opinion just the opposite of that expressed by Mr Baldwin. All 

 the phenomena in that area show that the ice was "alive" even 

 at this late time in the retreat. It built frontal moraines; it 

 maintained its frontage for some time along the margin of 



