Chapter 1 



E'HYSIOGRAPHY OF THE HUDSON AND OHAMPLAIN 

 VALLEYS IN RELATION TO THE CONTROL OF GLACIAL 

 PRODUCTS 



PHYSIOGRAPHY OF THE HUDSON VALLEY 



The valley of the Hudson river, from the point of view of the 

 stream bearing that name, is a. geographic group of drainage 

 slopes whose axial trough, if we except the Adirondack portion 

 of the river, has a nearly north and south direction, traversing 

 a geologic area of variable structure formed of rocks of widely 

 different ages in its various parts, and having different degrees 

 of topographic development. The order and structure of the 

 rocks of its valley have long been portrayed on the geologic maps 

 of the State, and the contour of the land forms bordering the 

 river are now faithfully delineated on topographic maps, but the 

 precise history of the origin of this river has not been determined. 

 The reader must, therefore, be content with a statement of the 

 main facts in the form and cross-section of this valley and it is 

 important that these features should be understood in following 

 any attempt to unravel the Pleistocene history of the valley, 

 particularly in relation to its occupation by the last ice sheet 

 and to the retreat of that ice from eastern New York and the 

 subsequent invasion by the sea of at least the neighboring Cham- 

 plain valley. 



For the greater portion of its length, the Hudson valley con- 

 sists of a gorge within a valley. Both" the valley and the gorge 

 vary so greatly in minor detail from point to point that it is desir- 

 able first to generalize the parts in which the valley, as a whole, 

 has something like a characteristic geologic and geographic ex- 

 pression. From this point of view there are four longitudinal 

 divisions of the Hudson valley each with a landscape somewhat 

 peculiar to itself. 



longitudinal divisions of the Hudson valley. The four segments 

 of the Hudson valley above referred to comprise two regions of 

 mountainous relief and two of lowlands, one of the latter being 

 relatively roughened by somewhat advanced dissection. 



