340 NEW YORK STATE MUSEUM 



terraces. This we may assume to be the norm for it is not likely, 

 except in rare cases, that the upper cliff will retreat so rapidly 

 that the space between the two becomes broad enough to have the 

 characters of a second inner lowland, separating two cuestas. 

 Conditions of multiple cuestas exist, as for example the two 

 cuestas of the ancient (Postpaleozoic) coastal plains of central 



Fig. 213 Outcrops of hard strata (2 & 3) after peneplenation to dotted line in fig-. 212 



England, described by Davis 1 , or the Niagara and Onondaga cues- 

 tas of western New York. 2 Such conditions are explainable in 

 one of two ways. Peneplenation obliquely across the strata and 

 recarving of the valleys on the softer beds. This appears to have 

 been the method which has given rise to the repeated cuestas of 



Fig. 214 Two escarpments resulting from erosion on soft strata after peneplenation 

 (compare dotted lines of fig. 213) 



western New York. This method is illustrated in the above 

 diagrams [fig. 213, 214] and will be more fully discussed below. 

 A partial elevation of the coastal plain may occur and while a 

 cuesta, topography is gradually carved out of the strata of this 

 plain, a new coastal plain may be deposited with the older one for 

 its shore and old land. Then on a second elevation the cuesta 

 topography may be carved out of the later coastal plain as shown 



'Textbook of Physical Geography. 



2Grabau. Geology of Niagara Kails. N. Y. State Mus. Bui. 45. p. 44. 



