188 



DYNAMICAL GEOLOGY. 



The results are the more marvelous in that they are the work of the later 

 part of geological time, commencing after the Tertiary era had begun. They 

 show that to produce a mountain group, with summits thousands of feet above 

 the plain around, it is only necessary that subterranean action should make 

 a plateau of sufficient extent and elevation. Through the rains, the sculp- 

 turing will all be done in time. Many of the so-called mountains of Colo 



179. 



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View of peaks and ridges within the Colorado Cafion, south of the Kaibah Plateau. W. H. Holmes. 



rado and other parts of the Rocky Mountain region, and some of those in 

 eastern America, as the Catskills in New York, and parts of the Alleghanies, 

 consist of nearly horizontal strata, and are examples — not of mountains made 

 by upturning, but of plateaus carved into models of mountains. Scotch val- 

 leys and elevations so modeled gave Hutton the first right ideas on this subject. 

 The "harder" rocks in the scenes described, it is to be understood, are 

 not granite, gneiss, syenyte, and the like ; they are not rocks of any particular 

 kind. Granite may constitute the loftiest and boldest of ridges and moun- 



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