THE ADIRONDACK MOUNTAINS 



73 



these tide-water beach deposits show how much lower the land was 

 during the time of greatest submergence, and that the subsidence 

 was most toward the north. 



The most recent movement of the earth's crust over the area of 

 northern New York was the very recent gradual elevation which 

 expelled the tide waters and left the land at its present altitude. 

 The increasing altitudes of the beaches northward prove that the 

 greatest upward movement was on the north. This recent elevation 

 is also clearly registered by the delta sand plains which were formed 

 in the larger glacial lakes of northern New York as, for example, 

 Black lake and Lake Pottersville already described. The delta 

 deposits of these extinct lakes gradually increase in altitude several 

 feet a mile northward. 



Fig. 15 The time of the Nipissing Great Lakes and Champlain submer- 

 gence. The shaded area on the east was covered by sea water. 



(After F. B. Taylor) 



