PHYSIOGRAPHIC RELATIONS OF SERPENTINE 



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almost precipitous, the boldness of the ridge being, in general, one 

 of its most impressive aspects. It is noteworthy, also, that it con- 

 sists entirely of serpentine and embraces the entire known area of 

 the serpentine. The Manhattan schist on the southeast side of the 

 ridge and the Triassic trap and sandstone on the northwest side, are 

 wholly outside of the highland area, being strictly confined to the 

 lowland or, rather, to the underlying peneplain, although the trap, 

 at least is far more resistant than the serpentine. 



The serpentine relief clearly holds the general or formal relation 

 of a monadnock to the Cretaceous peneplain above which it towers; 



\*- 



•Vert. = <foof*. 



Fig. I. — Cross-section of Staten Island, showing the geologic and topographic 

 relations of the stock of serpentine. 



and this most obvious interpretation of the Staten Island bedrock 

 relief demands the first consideration. In this connection it may 

 be noted that serpentine, owing to its insolubility and general 

 chemical stability, imperviousness, massive structure, and tight 

 joints offers greater resistance to erosion than its inferior hardness 

 would indicate ; and it is not improbable that in the relatively inert 

 nature of the stone we have an adequate explanation of some of its 

 topographic reliefs, especially where the surrounding formations are 

 of a weak and yielding character. A general survey of serpentine 

 occurrences, the world over, shows, however, that, almost regardless 

 of the geologic environment, they are, if of a massive character 

 (stocks, dikes, etc.), characterized by topographic relief. 



