THE ADIRONDACK MOUNTAINS 57 



This domelike character of the Adirondacks has apparently been a 

 very persistent feature for many millions of years, or at least since 

 the beginning of the Paleozoic era, and this in spite of profound 

 erosion. It will be recalled that the interior of the region was a 

 large, low island in the midst of the early Paleozoic seas. Uplift of 

 northern New York toward the close of the Paleozoic era, and con- 

 sequent removal by erosion or much of the bordering Paleozoic strata, 

 no doubt renewed the prominence of the Adirondack dome. Next, 

 during the long time of the Alesozoic era, the region was worn down 

 to a fairly good peneplain except from the central to the east- 

 central portion. Then came the late Mesozoic or early Cenozoic 

 uplift of this peneplain, apparently with greatest elevation corres- 

 ponding roughly to the present north-northeast by south-southwest 

 main axis (see above) which extends across the Adirondack region. 

 Naturally the streams which began to operate upon this newly 

 upraised domelike surface flowed outward from the highest or 

 central to eastcentral Adirondack district. During the long Ceno- 

 zoic time, the weak Paleozoic strata were still further removed from 

 the sides of the ancient dome of the Adirondack (Prepaleozoicj 

 rock, thus accentuating it as a topographic feature and permitting 

 the streams to adjust themselves to a more and more perfect radia- 

 tion in all directions from the higher central portion. Certain im- 

 portant drainage changes have been brought about by the recent Ice 

 Age and these will be described below, but they do not seriously 

 afifect the conclusions just reached regarding the drainage. 



Immediately after the uplift of the peneplain, some of the 

 easterly headwaters of the Susquehanna river came out of the 

 southwestern Adirondack district. Among the evidences are the 

 following : The Mohawk valley had not then come into existence 

 the slope of the upraised peneplain surface was there southward; 

 and the numerous sources of the Susquehanna which now rise at 

 the very brink of the Mohawk valley on the south side strongly 

 suggest that these streams once started some miles farther north- 

 ward. As a result of the development of the Mohawk valley, these 

 upper waters of the Susquehanna in the southern Adirondacks have 

 been captured and diverted into the Mohawk river. 



The Great Ice Age 



Ice extent and direction of movement. The Quaternary is the 

 last period of earth history and it still continues for it has led up to 

 the present-day conditions. This period was ushered in by the 

 spreading of vast ice sheets over much of northern North America 



