PHYSIOGRAPHIC STUDIES IN PENNSYLVANIA 



477 



Cross Mountain has resisted erosion, and its flat, broad top is prob- 

 ably a remnant of the old peneplain surface. 



Northward beyond Cove Gap the structure of Cove Mountain 

 is synclinal, but is compHcated by faulting. Although some of its 

 summits rise to 2,050 feet, its general elevation is not over 1,800. 



The western monoclinal ridge, Tuscarora Mountain, is more 

 massive than Cove Mountain because the rocks are not so steeply 

 inclined and have withstood erosion better. Consequently it has a 

 greater altitude, ranging from 1,950 to 2,050 feet, and a smoother 



The middle-ground is the gently rolling upland north of St. Thomas. 



crest line. Northward this monoclinal mountain forks by the develop- 

 ment of a synclinal valley and another monoclinal ridge on the western 

 side, the eastern ridge becoming anticlinal for a short distance. 

 The anticlinal portion of the ridge is 2,450 feet in elevation, and is 

 very broad and flat-topped. From its summit one looks over the 

 tops of the other ridges, whose general level is 300 and more feet 

 lower. It is evident that this peak was a monadnock in the old pene- 

 plain. Its broad, rounded character is due to its partial reduction 

 to the graded plain. Northward the eastern limb of the anticline 

 is faulted off and the ridge continues as a monocline at about 2,250 

 feet elevation. 



The monoclinal ridge, which branches off to the west, has an 



