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



till, sometimes of stratified drift, and sometimes of a mixture. They 

 vary in height, breadth, and details of form, but are most commonly 

 distinct ridges with undulating crests not more than 20 or 30 feet high. 

 While in some cases they have the appearance of erosional forms, as if 

 carved out of drift by streams descending the hill slope diagonally along 

 the margin of the ice tongues, they are more commonly evidently of 

 constructional origin. These forms are interpreted as marginal moraines 

 built along the side and end of minor tongues which extended from the 

 main valley tongues into the lateral valleys. In fact, in some cases the 

 ridges are directly continuous with lateral moraines of the main valleys 

 from which they extend, with greatly increased slope, often descending 

 as much as 100 or 200 feet in less than half a mile. 



A lateral moraine of one of the main valleys is not represented in the 

 side valleys by a single ridge, bub by a series of diagonally descending 

 ridges, radiating, fan-shaped, from the main valley lateral moraine. A 

 lateral moraine whose ridges and valleys on the main valley wall occupy 

 continuously a space of a quarter of a mile, with a vertical range of 100 

 feet, may, Qn entering a side valley, fray out into a dozen or more mo- 

 rainic ridges or strands, spread over a space of fully a mile. These 

 frayed moraines, which where best developed resemble a rope, the 

 strands of which are untwisted and spread apart, are found in many of 

 the valleys of the quadrangle, and are one of the most characteristic 

 morainic features of the area. 



It is evident that the separate strands represent halts in receding 

 tongues which extended into the lateral valleys. The distance between 

 the strands represents the distance through which the ice front retreated 

 horizontally during a vertical drop of a certain related number of feet 

 on the main valley side. The ridges of which the lateral moraines of 

 the main valley are composed are undoubtedly the correlative of the 

 strands of the lateral valleys ; but in the lateral moraines of the main 

 valley the ridges are so close together and so interwoven that they can 

 not be separated. How many times a foot of vertical recession in the 

 main tongue is multiplied in the horizontal recession of the lateral 

 tongues, as indicated by the strands, is uncertain ; but it is evident that 

 the amount varies with the width of the deflecting valley, the slope of 

 its sides, its bottom slope, and the angle and direction of ice approach. 



Moraines of lateral Tongues 



Into the larger valleys tributary to the main Cayuga and- Seneca 

 troughs the ice swung so far as to destroy the distinctly frayed appear- 

 ance of the morainic strands so characteristic of the smaller valle3's. In 

 such places distinct morainic bands and moraine terraces descend fairly 



