226 R. S. TARR — MORAINES OF SENECA AND CAYUGA LAKE VALLEYS 



northernmost portions of the valley-bottom moraines, which are, as 

 would be expected from this theory, much less well developed than those 

 portions farther south to which the definite lateral moraines descend. 



Borings in the moraine, which attain depths of from 100 to 400 feet, 

 together with cuts at the surface, prove that the morainic materials in 

 this valley-bottom complex are very variable in kind and in position. 

 Till is revealed in some of the cuts, but the moraine is largely composed 

 of stratified clay, sand, and gravel. Small cuts often reveal two or three 

 different kinds of drift, and these are usually confusedly thrown together. 

 Both faults and crumpling are frequently revealed in the cuts, proving 

 movements subsequent to deposition. While some of the faulting is 

 undoubtedly associated with recent slipping, most of the deformation of 

 the layers is evidently due to conditions associated with the morainic 

 accumulation, such as the shove of the ice tongue or of icebergs and the 

 melting out of stranded ice blocks. 



In topography there is much irregularity and usually little appear- 

 ance of system. In general the moraine consists of a series of hummocks 

 and short, irregular ridges, some of which rise fully 200 feet above the 

 valley bottom. The overlapping of the hummocks and ridges has given 

 rise to many kettles, some of large size, in which swamps and ponds 

 occur where the material inclosing them is not too gravelly. Stream 

 erosion has in places deeply dissected the unconsolidated morainic de- 

 posits, adding greatly to the topographic irregularity. By the slipping 

 down of the sides of the small, steep-sided valleys a very perfect type of 

 landslide topography is often caused. 



The valley-bottom moraine varies in character from south to north, 

 or between the divide and its northern edge, where it disappears beneath 

 the modern deltas of Cayuga and Seneca lakes. It exhibits three quite 

 different types of morainic form, most perfectly developed in the Cayuga 

 valley. The southernmost of these is the most normal morainic type, 

 in which the lateral moraine terraces extend into perfect terminal mo- 

 raine loops. Where best developed, as on the divide south of Cayuga 

 lake, there is a crescentic ridge, concave toward the north, and with out- 

 wash gravel terraces extending southward from each end. Near the 

 middle the distinct ridge form disappears, being replaced by a maze of 

 kame moraine, with many gravel hillocks and deep kettles. Just north 

 of this are one or two less perfect terminal moraine loops. These loops 

 were built in the air and not in lake water. 



Farther north in each valley, but especially in the Cayuga valley, 

 there is a series of broad, rather flat-topped ridges, roughly crescentic, 

 with concave faces toward the north, and with crests reaching to a nearly 

 uniform level. These are interpreted as the result of ice stands in a 



