90 NEW YORK STATE MUSEUM 



lake spread out over the sites of the present Paradox, Brant and 

 Loon lakes. Figure 9 shows the general extent of the waters of 

 this great lake. 



Glacial Lake Pottersville came into existence after the retreat of 

 the ice because of a dam, probably morainic, across the Schroon 

 valley east of Chestertown. 



The former existence of this large body of water is demon- 

 strated by the presence of numerous almost perfectly preserved 

 very typical delta sand flats or plains at nearly accordant levels. 

 Such deposits must have formed in standing water. In the 

 vicinity of Pottersville the highest water-laid lake deposits are a 

 little beloiw the 900- foot contour; near Schroon Lake village they 

 are at about 920 feet, and at North Hudson about 960 feet. In the 

 Schroon valley of the Paradox Lake quadrangle there is an almost 

 continuous succession of finely developed sand flats or terraces. 

 The northward increase in altitude of these high level lake deposits 

 is due to postglacial differential uplift of the land with a northward 

 increase at the rate of several feet a mile. This harmonizes with 

 similar findings regarding postglacial changes of level in the Cham- 

 plain valley. 



A fine section exhibiting the structure of the delta material occurs 

 along the state road just west of Schroon Lake village. The delta 

 terrace is well displayed for 2 miles northward from the village, 

 several kettle-holes occurring on it, these having probably resulted 

 from the melting of stranded icebergs which had been surrounded 

 by, or possibly buried under, the delta sands. The steep eastern 

 front of this terrace, so clearly shown on the contour map for 2 

 miles northward from the village, is the result of erosion by the 

 meandering Schroon river. 



Glacial Lake Pottersville was destroyed as such by cutting down 

 its outlet east of Chestertown. Schroon lake is but a remnant of 

 the former great lake. 



Glacial Lake Minerva. This former lake is so named because it 

 lay in the valley of Minerva stream in the town of Minerva. 

 Moxham pond is a tiny remnant of this body of water which was 

 fully 6 miles long. The area of the lake was almost exactly the 

 same as that of the area of Pleistocene represented on the geologic 

 map. A morainic dam at Olmstedville was quite certainly the 

 cause of the ponding of this water. At the village, Minerva stream 

 has cut a deep channel through this morainic deposit, and thus the 

 lake has been drained. The water level stood at what is now the 



