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FIRST YEAR SCIENCE 



the general elevation of the country is great, as in the 

 lofty regions of the Rockies, an elevation to be termed a 

 mountain must rise to a striking height above the gener- 

 ally elevated surface, which is itself nearly everywhere 

 more than 4000 feet above the sea. 



195. Structure of Mountains. Mountains are the results 

 of deformations in the earth's crust, due to causes not 

 fully understood and the study of which is a part of geology. 



APPALACHIAN PLATEAU. 

 A range of old mountains greatly reduced in height. 



The crust of the earth has been folded, pushed up, crumpled 

 and in many ways distorted so -that some portions have 

 been elevated to a considerable height above sea level. 

 Where these elevated portions have not remained long 

 enough to be worn down, they form mountains. 



All lofty mountains have been elevated in comparatively 

 recent geological time, but this of course means millions 

 of years ago. If mountains now lofty were geologically 



