REPORT OF THE DIRECTOR I917 



139 



The Origin of Lake Clear 



The great sand plain, left by the Saranac waters about the junction, 

 is without much question fairly thick and buries a fault line valley 

 that may have been a preglacial stream course. The rock bottom 

 of this valley may have been deepened at the spot where Lake Clear 

 is now situated by virtue of the weakness of the rocks at the crossing 

 of the two fault lines (see petrological map) , enabling the glacier to 

 hollow out a basin. At this point, when the glacier was melting it 

 perhaps left a block of ice in the depression which eventually became 

 buried by the outwash and lake sands. The block was thus placed 

 in a natural refrigerator and hence remained unmelted long after 

 the withdrawal of the ice sheet and the draining away of the Saranac 











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.1 



Fig. 2 Diagram illustrating the origin of Lake Clear. BR=bedrock (Anor- 

 thosite), F, F=fault line, I=buried block of glacial ice, T=till, SS=stratified sand, 

 L=lake (a stage in the Saranac glacial waters), B, B=beaches of the lake. 



The glacier excavated the basin in which a block of ice was left on retreat. 

 The block became covered by ground moraine (till). The Saranac glacial 

 waters then deposited fine sand on top of the till. When the ice block melted 

 it left a depression in which Lake Clear accumulated. 



waters. In time, however, it melted, lowering the surface, forming 

 a depression which became filled with rain water, and marking the 

 beginning of Lake Clear. There are a large number of these ice- 

 block kettle holes, as they are called, all about Lake Clear, in the 

 junction plain, and on the moraines, but in most cases they are 

 small topographic features. 



With the extinction of the Saranac waters we should have to pass 

 to other districts to follow the succession of glacial lakes in the 

 central Adirondacks, but as they have no significance here they will 

 not be discussed. 



