260 i 



i 



by the occurrence upon the highest level of a sharp kettle hole 300 feet in 

 diameter and 25 feet deep, marking the place where a detached ice block 

 stranded and melted. 



The occurrence of kettle holes in deltas is not uncommon. 1 A remark- 

 able ease of this kind has been described by the writer where an area of 

 ten acres of delta surface is thickly pitted with small kettles. 2 (Fig. 4.) 

 This delta is the joint product of a land stream and a valley glacier which 

 contributed ice blocks and an undetermined portion of the permanent ma- 

 terial. There are probably many intermediate forms between such a 

 morainal delta and one due wholly to stream work. 



.... *" . <-'"•„. 



Fig. 5. Outer Face of Morainal Delta. Fan in front of notch. 



When lake waters are withdrawn the bisection of a delta may result in 

 the formation of an alluvial fan in front of it. This gives a characteristic 

 combination of notched delta and fan. (Fig. 5). The fan of Mill Creek at 

 the foot of Honeoye Lake is a mile in diameter, and is responsible for the 

 existence of the lake, to which it acts as a dam. The fan of Canadice out- 

 let bears a similar relation to Hemlock Lake, which, however, is too deep 

 to owe its existence wbolly to that cause. 



Deltas occasionally take the form of long, narrow ridges upon one or 

 both sides of a stream, resembling the natural levees in "the goosefoot" 



1 Fairchild, Journal of Geology, Vol. 6, p. 589. 



2 Bulletin Geological Society of America, Vol. 15, p. 457. 



