﻿I56 NEW YORK STATE MUSEUM 



and if that gorge represents stream erosion to such depth (over 750 

 feet) it would indicate a gradient of nearly 300 feet to the mile 

 for the last 2 miles of the Moodna — a condition to say the least 

 decidedly unfavorable to the development of a flat-bottomed valley. 



Of course, if the profile as determined can be assumed to run 

 exactly parallel to the old stream channel for half a mile it would 

 be less surprising. But even then it is too flat. For so short a dis- 

 tance from the Hudson gorge the gradient ought to be much 

 greater than the variation observed in the Moodna channel. There 

 are certainly reasons in the structural geology favoring a northeast 

 course instead of one parallel to the profile line. And if the 

 stream really did flow across this structure, the differences of 

 hardness of beds ought to have encouraged a much greater differ- 

 ence in depth of channel than the profile presents. With structures 

 all running northeast there is every reason to expect the stream 

 to follow them. 



Recent exploratory data strongly supports the theory that the 

 Hudson gorge at Storm King gap is widened and possibly some- 

 what overdeepened by glacial ice. Under normal stream relations 

 one might consider the Moodna a tributary hanging valley, itself 

 rounded and smoothed to a broad U-shape by ice. This would be 

 a very easy solution if it were not for the fact that this tributary 

 Moodna opens into the Hudson as a reversed stream, i. e. it opens 

 against the flow of the Hudson and more or less directly against 

 the known ice movement. Tit can not be a hanging valley there- 

 fore of the normal sort. If a hanging valley of ice origin at all 

 it would necessarily be one therefore gouged out by ice moving 

 from its mouth toward its head, a case that so far as the writer 

 knows has never been observed. The chief objection to this theory 

 is that in no other gorge or channel (with one exception, the Hud- 

 son at Storm King gap) anywhere in the region, so far as known 

 is there any evidence of serious modification of an original stream 

 channel by the ice invasion. Of course, the axis of the valley is 

 favorable and the situation is peculiar in that it parallels the High- 

 lands front in this vicinity and the action of the ice may be as- 

 sumed to have been somewhat concentrated along this margin be- 

 cause of the obstruction. 



Inner notch or secondary gorge. Those who habitually em- 

 phasize ice action would no doubt choose to regard this whole val- 

 ley as shown in the profile, as chiefly glacial in character and 

 origin. If that explanation is the true one, then it must be ad- 

 mitted that a deeper smaller inner notch or gorge is unnecessary 

 and indeed unlikely. 



