THE GREAT RELIEF FEATURES OF THE LAND 277 



maturely dissected. There are many faulted mountains in 

 the Great Basin region, where they are perhaps the leading 

 type of mountain structure (Fig. 289). 



FIG. 289. Diagram showing the general arrangement of block mountains 

 in the Great Basin. Each mountain block is tilted in the direction indi- 

 cated by the light slanting lines. The broken lines show the profiles of 

 the mountains before erosion. The dotted portions of the diagram rep- 

 resent the accumulation of waste. Length of the section, 120 miles. 

 (Gilbert.) 



Folded mountains. Mountains consisting of a series of 

 earth folds are a common type. In the Jura Mountains of 

 France and Switzerland, open, symmetrical anticlines form 

 parallel ridges, separated by synclinal troughs (Fig. 290). 

 The structure of most folded mountains is much more com- 



FIG. 290. Diagram showing symmetrical folds of the Jura Mountains. 



plex than that of the Juras. In parts of the Appalachians, 

 for example, the folds are closed, unsymmetrical, and often 

 overturned, and the structure is complicated by many faults, 

 some of which have a vertical displacement of several thou- 

 sand feet (Figs. 291 and 292). Here the strata were sub- 



FIG. 291. Structure section in the Appalachian Mountains. South- 

 western corner of North Carolina. (From Nantahala, N. C. Tenn., 

 Geologic Folio, U.S. Geol. Sun.) 



jected to much greater compression than in the Jura Moun- 

 tains. Most of the strike faults in folded mountain regions 

 are overthrusts (Why?). Where the folding of the beds 

 was intense, the larger folds are composed commonly of a 

 diminishing series of minor folds (Fig. 291), the smallest of 



