GEOLOGY OF THE WEST POINT QUADRANGLE, NEW YORK II 



The fact that the Hudson is a drowned river affects its present 

 appearance and behavior to a much greater degree than is usually 

 appreciated. Although the Highlands area is 50 miles from the 

 sea, the water level in the river is essentially sea level and is affected 

 by the daily tides and is also contafpiinated by the mingling of waters 

 from the sea. Superficially the gorge does not appear extraordinary, 

 but the rock floor of the trench is very deep, though heavily filled 

 with drift and silts and the present water level of this drowned 

 river materially reduces the visible depth of the gorge and thus 

 in part destroys its conspicuousness. 



The exact depth of the gorge is not known at any point, but 

 explorations that have been conducted in connection with the con- 

 struction of the Catskill aqueduct have shown that it is several 

 hundred feet deep and that at the northern gateway between Storm 

 King and Breakneck mountain it extends more than 765 feet below 

 the present water level. Boring operations at that point penetrated 

 to this depth without encountering bedrock, and indicate that the 

 gorge is filled with a great variety of drift materials and water-laid 

 deposits. The fact that other tests of the rock floor showed solid 

 rock at an estimated depth of 950 feet and the fact that the Catskill 

 tunnel was actually constructed in solid rock at a depth of iioo feet 

 proves that the rock floor river bottom is somewhere between 765 

 and 950 feet. (For a fuller discussion of this question, see the 

 chapter on Engineering geology under the item Storm King 

 crossing.) No one knows whether or not the gorge is as deep as 

 this throughout the Highlands, but this is probably its deepest and 

 widest point. The gorge at water level is 3000 feet wide on the 

 average. 



There are three remarkably sharp turns or angles, at West Point, 

 at Anthony's Nose and at Dunderberg. These changes in course 

 undoubtedly are induced by the structure of the rock to which the 

 river has become somewhat adjusted. But the river does not follow 

 any single structure entirely across the Highlands belt, and thus it 

 appears that these structures are incidental rather than primary con- 

 trols in the original course of the river. 



Terraces about 150 feet above sea level are very well marked 

 within the Highlands belt at certain places, but it is a very striking 

 thing indeed that there is almost no trace of terrace development at 

 Storm King, Crows Nest, Dunderberg. Anthony's Nose or Bull Hill. 

 In other words, the massive granite belts show absolutely no develop- 

 ment of terraces whereas terraces are prominently developed on the 



