MOUNTAINS AND PLATEAUS 



361 



limestone. A load of shot, representing the weight of the overlying 

 strata, was then placed on top of the layers. Upon the application 

 of lateral pressure it was found that, by varying the rigidity and 



Fig. 350. — Machine for experimenting in mountains of folded structure. 

 (U. S. Geol. Surv.) 



thickness of individual layers and of the layers as a whole, the phe- 

 nomena observed in folded regions were reproduced. A study of the 

 apparatus (Fig. 350) gives a better idea of the conditions of the experi- 

 ment than a written description. 



ANC/ENT CO/VT/NENT 



ANC/Efi/T CONT/f/ENT ' FOLDED ZOUE 



SURFACE FACTS AND UNDERGROUND INFERENCES 



ANC/Ef/T CONT/A/EHT 



RESTORATION OF SURFACE, EXCLUDING EROSION 



'ZONE OE POLOI/VG 



RESTORATION OF RELATIONS OF LAND AND SEA AND OF POSITION OF STRATA PRIORTO FOLDING 



Fig. 351. — Diagrams showing the theoretical history of a folded region. The 

 lowest figure shows the region when the present site of the mountains was a great 

 geosyncline in which a load of sediment, 25,000 to 40,000 feet thick, had been laid 

 down. The middle figure shows the region after it had yielded to great lateral pres- 

 sure and had been folded and faulted. The upper figure shows the region as it is 

 to-day. (Redrawn after Willis.) 



