648 H. L. ALLING GLACIAL LAKES OF CENTRAL ADIRONDACKS 



an average direction of about south 45° west, influenced, no doubt, by 

 radial flow and to a greater extent by the topographical features that 

 culminate in the major faults which make the region interesting to the 

 physiographer. The striae in the valleys are, undoubtedly, due to the last 

 stages of the ice-movement, for subsequent weathering has entirely de- 

 stroyed the glacial scratches on the mountains which would have indicated 

 the general direction of the ice-flow. 



EROSIONAL WORK 



Although there is a difference of opinion as to the destructive power 

 of the continental glacier, the mountains must have been scraped clean 

 of the decomposed rock surface resulting from atmospheric action. The 

 bare slopes of Pitchoff Mountain, on the southern edge of the Lake Placid 

 sheet, furnish an excellent example of such action. 



The many amphitheaters and little rocky pockets on the mountain 

 sides, so noticeable in the Adirondacks, are due, in all probability, to the 

 erosive action of ice. These cirques have been by some attributed to the 

 work of local glaciers. 3 Excellent examples are visible on the slopes of 

 the highest mountains, such as Giant, the Gothics, and Basin, as well as 

 on the sides of Whiteface and Sentinel. 4 



The origin of rocky pockets occupied by ponds on the southwestern 

 slopes of some of the mountains is not clearly understood, but the pluck- 

 ing action of the ice may be regarded as a contributing cause. Lost Pond, 

 in the southwest corner of the Ausable sheet; Little Pond, on Ellis Moun- 

 tain, and the Giant' s Washbowl are typical. The almost universal posi- 

 tion of these little lakes on the southwestern slopes of the mountains 

 gives weight to such a theory. 



In pushing through the major faults, such as that of the Cascade Lakes, 

 the Wilmington Notch, and the fault of the Middle Kilns, the ice carried 

 Avith it the talus material that had accumulated during interglacial 

 periods; freshened up the valley walls, and left U-shaped valleys, blocking 

 both ends with crescent-shaped moraines as it retreated. 



The occurrence of glacial boulders is quite common, some of which 

 appear to have been transported great distances, while others can be traced 

 to parent ledges in the neighborhood. In Keene Valley the boulders are 

 often quite large, sometimes as large as a small house. They are much 

 more plentiful on the west side of the valley than on the other, again 

 indicating the south westward ice-flow. Bounded boulders of Potsdam 



8 I. H. Ogilvie : Glacial phenomena in the Adirondacks. Jour. Geol., vol. 10, 1902, pp. 

 397-412. 



* J. F. Kemp : N. Y. State Mus. Bull., vol. 21, p. 62, 



