6o XEW YORK STATE :MUSEUM 



pond, and west of Salmon pond. In many other places more or less 

 exfoliation was observed, but the ones above mentioned are the 

 most interesting. 



Influence of Glaciation 



The glaciation of the quadrangle having already been described, 

 it is now necessary to refer briefly to only a few effects of the 

 ice sheet which have modified the relief. 



Ice erosion appears to have modified the rehef to a very minor 

 extent only. The soil and rotten rock were largely scraped off down 

 to the fresh rock particularly on the higher lands. Mountain masses 

 may have been somewhat rounded off. As already pointed out, 

 the basins of Long lake, Blue Mountain lake, and the third of the 

 Chain lakes may have been locally slightly deepened by ice erosion. 



The principal topographic effect of glaciation has been the almost 

 universal tendency to accumulate the scraped oft" soil and rotten 

 rock in the valleys. Accordingly the rehef is lower now than at the 

 time immediately preceding the ice age. Most of the valleys contain 

 large accumulations of glacial debris, stratified and unstratified, with 

 thickness up to several hundred feet. Most of the streams have 

 only here and there cut through these deposits to the underlying 

 rock. 



The Cretaceous Peneplain 



It is well known that toward the close of the Cretaceous period, 

 a more or less well-developed peneplain existed over the northern 

 Appalachian district, central and southern Xew York, the western 

 side of the Adirondacks, and southern New England. As a result 

 of the uplift and dissection of this great peneplain, the chief relief 

 features of the northern Atlantic coast have been produced. Any 

 very satisfactory' evidence for a well-developed Cretaceous pene- 

 plain over the central and eastern Adirondacks has so far not been 

 obtained, and the topography of the Blue ^Mountain quadrangle does 

 not throw much light upon the problem. The most probable 

 explanation is that the great masses of very resistant igneous rocks 

 in the Adirondack region favored the existence of rather numerous 

 and prominent monadnocks which rose above only a crudely devel- 

 oped peneplain surface. Hence it is difficult, if not impossible, to 

 locate remnants of the peneplain surface with any certainty. 



Within the Blue Mountain quadrangle, many mountain summits 

 lie at altitudes of from 3000 to 3500 feet, with many others only a 

 little higher or lower. This is well shown in the large mountain 



