REPORT OF THE DIRECTOR I919 53 



ends of the hanging valleys is the distinctive mark of a notable inter- 

 ruption in the stream erosion and weathering development of the 

 side valleys; and the measure of the depth and enlargement of the 

 side valleys indicates the degree to which the postglacial stream 

 drainage has attained readjustment to the accordant slopes normal to 

 purely stream-erosion and weathering cutting of valleys. 



The morainic loop. Continuing up the trough valley there is 

 next encountered the morainic loop or terminal moraine accumula- 

 tion developed at the end of the Onondaga lobe during the halt 

 period. This is at once the most conspicuous and spectacular 

 feature of the glacial series, for it blocks the valley completely with 

 a massive earth barrier. Its inner or northern side, against which 

 the ice end rested, is so steep as to make it a very noticeable topo- 

 graphic feature. 



Plate 3 shows this steep front as viewed from the west end of 

 the moraine itself ; plate 9 is a view also from the west side of the 

 valley but from a point farther north along the Onondaga trough 

 side, and therefore shows better the general configuration of the 

 mass. The moraine makes a vast amphitheater of the head of the 

 valley on its north side, with sides 300 feet high in the steeper upper 

 part and a further slope of 200 feet more in the gently inclined 

 portion at the base. 



Against these slopes the ice tongue rested while discharging the 

 material forming the moraine. The form of the slopes may, there- 

 fore, be regarded as a mold of the form of the ice itself for the 

 depth up to which the moraine stuff was banked against its front. 

 Beginning at the elevation of the relatively level crest Une of the 

 moraine, the ice is to be conceived as rising steeply northward, and 

 within a few miles attaining sufficient thickness to fill the trough 

 valley to the height of its bounding walls. This would mean that 

 near the moraine front there was an ice slope of perhaps 400 feet 

 down to the moraine summit. 



The terminus of the lobe would thus have a very distinct wedge- 

 shape, convex on both sides, like the blade of an axe made very thick 

 behind the edge, the horizontal front edge of the wedge being dis- 

 posed always along the crest line of the moraine during the progres- 

 sive stages of its upbuilding in mass and height. Blocks of rock, 

 melting out of the ice above the level of the crest at any stage, would 

 roll and slide down the steep frontal slope of the ice until they 

 lodged on the moraine; melting water would wash down the finer 

 gravels and sand; drainage in streams of considerable volume at 

 each margin of the lobe would sweep down larger quantities of such 



