PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOROUGH OF QUEENS Gtti 



miles at the rate of 30 feet to the mile. Such an elevation of the 

 ice sheet increasing northward over the sound and on the mainland 

 would give great hydrostatic pressure to the subglacial drainage, the 

 elfect of which would be to produce violent discharge at the front 

 in any direction, outward or upward, in free coursing streams on 

 the one hand and in fountains along the crevassed, drift-blocked ice 

 margin on the other hand, in the manner of the discharge from the 

 border of the Malaspina glacier as described by Russell.^ An over- 

 laden stream, scouring the gravelly bed of the glacier and rising at 

 the front tlirough a sliaft to a point of discharge on the margin, 

 would drop that material at the margin in a high cone, whose ulti- 

 mate form would depend on the degree to wliich it was deformed 

 by irregular deposition on buried masses of ice, the melting of 

 w^hich would let down those huge kamelike heaps of gravel in the 

 form of mounds along the ice front. 



Distinction hetiueen outer and inner moraine. Two viery distinct 

 lines of moraines, designated as the inner and the outer, typically 

 developed on Cape Cod on the one hand and on Nantucket and 

 Marthas Vineyard on the other, have long been recognized by 

 American geologists, and have been traced with much certainty 

 across the intervening stretches of sea and land or islands to Long 

 Island, most successfully by Warren Upham,~ whose name and labors 

 must ever be associated with the glacial deposits of this region. 

 Mr Upham evidently regarded the inner of these two lines of 

 moraines as terminating, so far as its relief above sealevel is con- 

 cerned, at Port Jefferson. The morainal ridge which extends from 

 the vicinity of Coldspring to Xew York narrows was regarded as 

 the outer moraine. This interpretation has, so far as I know, ever 

 since been generally accepted,'^ and tlie moraines have so been repre- 

 sented on compiled maps, leaving as an unsolved problem the ques- 

 tion of what has become of so well defined a moraine as that which 

 from Port Jefferson eastward has been known as the inner moraine, 



r — ■ —— — — — — -~ ~~" ■ ■" 



1 Russell, I. C. Second expedition to Mt St Elias. U. S. geol. sur. 13th an. 

 rep't. 1893. pt 2, p. 81. 



- Upham, Warren. Glacial history of the New England islands. Am. geol. 

 1899. 24 : 79-89. 



^Chamberlin, T. C. U. S. geol. sur. 3d an. rep't. 1883. map, pi. 33. 



