ORIGIN OF FOLDED :\10UNTAINS ' 



By \V. F. Prouty 

 University of Norili Carolina 



I have chosen the origin of folded mountains as a subject for dis- 

 cussion for tlie reason that tliese great earth structures are of interest 

 to all of us, and because the theories of their origin are many and 

 Avidely divergent. For most of us the mountains are a great source of 

 inspiration and pleasure. Whether we see them from afar or near at 

 hand, there is always something about them that holds our attention. 

 We see in them the ever active forces of nature ; the rushing stream, 

 the avalanche, the massive glacier, the jagged peak, the lightning 

 flash, the ever-shifting clouds. From the earliest time man has 

 opposed his strength to the mountain mass and frequent!}^ he has 

 lost. 



Much of the history of the earth is written in the mountain rocks 

 and their structure. Man has learned much from this source but 

 he has yet much more to learn. Leonardo da Vinci, the great artist, 

 architect, and scientist, was convinced that the fossils in the rocks 

 of the high Alps were once sea shells. We know now that be was 

 right, that tliese shells were buried in the sands, clay, and ooze of 

 the sea bottom and later were elevated to their present position. Not 

 only were these sediments lifted, but they were folded, buckled, 

 sliced, and mashed, and in places greatly altered and injected by 

 igneous rock, so that the present mountain mass is a great structural 

 complex. Some mountains are less intricate in tlieir structure than 

 the Alps, but others are even more complex. 



From the study of mountains we get many facts. We find that 

 there are many active, unbalanced forces in the earth. The elevation 

 of the Colorado Plateau from below sea level to more than 8,000 

 feet above sea level shows a tremendous, persistent, and widesju'ead 

 vertical force. The rise and fall of many parts of the coast line 

 of Italy in historic time is a good example of the less constant ver- 

 tical forces. The folding, mashing, slicing, and shearing of the 

 rocks in many of the mountains is ample proof of the lateral com- 

 pressional forces in the earth's crust. Tensional forces, elsewhere, 



1 Presidential address delivered before the North Carolina Academy of Science, May 8. 

 1931. Reprinted by permission from the Journal of the EHsha Mitchell Scientific Society, 

 vol. 47, DO. 1, January 1932. 



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