MORAINES OF LATERAL TONGUES 221 



steeply to the valley bottom, crossing it in a series of crescentic loops 

 with hummocky and often kamey fronts, against which the ice rested. 

 In some cases there is a succession of these terminal moraine loops 

 connected with the ice stands of various levels. In one case, southeast 

 of Watkins, loops correlated respectively with 1,000-foot and 1,800-foot 

 moraines in the Seneca valley are 6 miles apart. From this it is con- 

 cluded that a vertical recession of about 800 feet in the main valley is 

 represented in a lateral valley of this kind and position by a horizontal 

 recession of the ice tongue of about 6 miles. 



Marginal Lakes 



Where such lateral tongues extended into valleys whose slope was 

 toward the ice, each of the stands of the successive ice levels interfered 

 with preexisting drainage, and the ice front was in standing water ponded 

 back by the ice dam. Into these ice-dammed lakes debris was poured 

 not merely directly from the ice, but by the marginal streams and by 

 streams from the land which the ice no longer covered. In the area of 

 the Watkins Glen quadrangle there is represented every gradation in 

 the filling of such marginal lakes, proving that this condition was a 

 common one during the various stands of the waning ice sheet. 



In some cases the lake filling was completed and broad plains of 

 outwash gravel built back of kamey ice-front moraine deposits. In such 

 cases the vallej' bottom consists of a series of terrace steps, the terrace 

 front being moraine and the successive terrace tops being determined 

 by the different levels of lake outflow. Not uncommonly alluvial fan 

 deposits, brought both by marginal and land streams, have raised the 

 filled lake plains still higher. Doubtless many of these filled lake plains 

 were partly supplied by feeding eskers, later buried beneath moraines 

 and lake fillings of lower ice stands, but in only one place was such a 

 condition discovered. 



Unequal Development of Moraines of valley Lobes 



In the lateral valleys it is almost universally the case that moraines 

 are much better developed on one side of the valley than on the other. 

 In one case, for example, a remarkably perfect kame moraine is present 

 on the north side of a valley, while moraines of the same ice stand on 

 the south side are either weakly developed sag and swell type or else 

 morainic terraces of no great width. There is probably from 20 to 50 

 times more material in the moraine of the northern than of the southern 

 side. At times this unequal morainic development is so marked that, 

 whereas well denned morainic strands descend one of the valley walls, 

 no traceable moraines have been detected on the opposite wall. 



