

STRUCTURE AND SURFACE FEATURES 397 
1. Folded Mountains—This type is much the most 
important, comprising, as it does, the greatest chains and 
ranges of the Old and New Worlds. The Alps, the Pyrenees, 
the Carpathians, the Himalayas, are all folded mountains, 
and the same may be said of the great mountain chains 
which extend almost continuously along the western borders 
of North and South America, and the corresponding chains 
and ranges of Eastern Asia and its archipelagoes. 
All these mountains, however much they may differ in 
configuration, are characterised by a well-marked geological 
structure. They are composed essentially of highly flexed 
and folded strata. No doubt they show other structures— 
besides being folded, the rocks are often traversed by dis- 
locations large and small, and by eruptive masses of different 
kinds. But it is the folded character of the strata which is 
the most essential and typical structure. Sometimes the 
folding is ofa simple enough type. Occasionally, for example, 
the rocks entering into the formation of a mountain range 
are arched up in one single broad saddleback or anticline 
(Gee ic 138). Or in place of a great geanticline we 

FIG. 138.—SECTION ACROSS THE. UINTA MOUNTAINS—A BROAD ANTICLINE 
BROKEN BY A DISLOCATION OR FAULT. 
may have a series of many symmetrical folds—the rocks 
rising and falling, as it were, in a succession of uniform 
undulations (see Fig. 139). But usually the structure is much 

FIG, 139.—SYMMETRICAL FOLDS OF THE JURA MOUNTAINS, 
a, @, anticlines ; s, s, synclines. 
more complex—the folds being no longer open and sym- 
metrical, but closely compressed and inclined at all angles, 

