THE ADIRONDACK MOUNTAINS 5I 



topographic (relief) features of northern New York, inchiding the 

 Adirondacks, as we see them today have been largely produced by 

 the erosion or dissection of this upraised peneplain. This being 

 so, are there any remnants of that upraised surface still visible? 

 Where best developed, in the northern Appalachians, the upraised 

 plain has trenches or valleys cut in the belts of weak rock to below 

 the surface of the plain, while the ridge summits at concordant 

 altitudes practically represent portions of the old peneplain surface. 

 In New York State the concordant altitudes are not so well shown 

 both because the peneplain was there not so well developed and 

 because the attitude of the rock masses was largely unfavorable to 

 the production of long, distinct ridges. Remnants of the peneplain 

 are, however, unmistakably present in New York as, for example, 

 on a very large scale over the southwestern plateau district covering 

 thousands of square miles where the highest points mostly reach 

 altitudes of about 2000 feet. The summit of the Tug Hill plateau, 

 just west of the Black River valley also lies at about 2000 feet and is 

 clearly a remnant of the upraised peneplain which formerly con- 

 nected with the southwestern plateau. As one looks out over the 

 western slope of the Adirondacks from the summit of the Tug 

 Hill plateau, he is impressed by the remarkably even sky line there 

 shown at an altitude of a little over 2000 feet. The central and 

 east-central Adirondacks are exceptional because considerable 

 masses there stood out above the general level of the old peneplain. 

 It is important to note that, as a result of the long time of erosion 

 before and during the Mesozoic era, the Paleozoic strata, which 

 had been deposited well over the borders of the Adirondacks, were 

 considerably removed. 



Since the actual work of erosion or dissection of the upraised 

 peneplain in northern New York took place during the next or 

 Cenozoic era, further discussion of this subject is reserved till the 

 consideration of that era. 



The great fractures (faults) of the southeastern Adirondacks. 

 Examination of the detailed topographic maps of the eastern and 

 southeastern half of the Adirondacks shows that there are many 

 ridges and valleys, streams and lakes, which trend in a north-north- 

 east by south-southwest direction. What is the explanation of these 

 features? This region has been extensively fractured or faulted. 

 In fact, the major relief features are largely dependent upon this 

 faulted structure. A few words of explanation regarding faults are 

 here in order. Whenever a fracture has developed in the earth's 

 crust and one portion of the earth has slipped by or been pushed 



