PHYSIOGRAPHIC STUDIES IN PENNSYLVANIA 479 



Schooley's Mountain, N. J., and Willis^ later called it the Kittatinny 

 peneplain after the mountain of that name. It has been traced east- 

 ward under the deposits of Cretaceous sediments on the eastern 

 border of the continent, and is therefore shown to have been formed 

 by aerial erosion while the land stood approximately 2,000 feet lower 

 than at present. The plain extended over the present Cumberland 

 Valley, where its surface was composed largely of Hmestone and shale, 



Fig. 3. — The Schooley peneplain preserved on Cross Mountain in the center, 

 with the lower comby ridge of Cove Mountain on the right. 



but in part, probably, of overlying quartzites. These rocks have 

 been removed during subsequent uplift and erosion. The resistant 

 quartzites forming the mountains have withstood erosion, and rise 

 approximately to the level of the former peneplain. The present 

 altitude of the plain in South Mountain is about 2,000 feet, and in 

 Tuscarora and associated mountains from 2,000 to 2,100 feet, which 

 may indicate that in the uplift there was tilting toward the southeast. 

 At lower altitudes in the mountainous areas there are broad, flat, 

 terrace-like features, which probably represent prolonged stages of 

 erosion during local halts in the elevation of the land. A broad flat 



I "The Northern Appalachians," National Geographic Monographs, Vol. I, 

 p. 189. 



