MOUNTAIN ORIGIN AND STRUCTURE. 



253 



There would be in the experiment, and much more would we expect 

 in Nature, some variety in the result depending upon the softness or 



Fig. 221. 



stiffness of the strata. This it is that gives rise to different types of 

 mountains. Sometimes the whole mass rises as one great fold (Fig. 220). 

 We have an example 

 of this in the Uintah 

 range, only that the 

 fold has broken down 

 on one side, forming a 

 great fault (Fig. 221). 

 Sometimes and of tener 

 there are produced 

 several open folds like 

 great earth-waves (Fig. 

 222). This is the case in the Jura (Fig. 223). Sometimes, and often- 

 est of all, there are produced many closely oppressed folds, as in the ex- 

 periment (Fig. 219, B). This is the case in the Coast Eange of Cali- 

 fornia (Fig. 224), or in the Appalachian (Fig. 225). Sometimes the 



Fig. 222.— Ideal Section of Jura if unaffected by Erosion. 



Fig. 223. — Section of Jura as modified by Erosion. 



mashing is so extreme that the sides are driven in under the swol- 

 len central parts, so that the strata are often reversed. This is the 

 case in the Alps (Fig. 226). 



Fig. 224.— Section of Coast Range, showing Plication by Horizontal Pressure. 



Proof of Elevation oy Lateral Pressure alone : 1. Folding. — It is 

 evident that foldings such as those represented in all the above figures, 



O 7 C B 3 2 / A 



Fig. 225.— Generalized and Simplified Section of the Appalachian Chain. 



