RELIEF FEATURES 



13 



Origin. Mountains are made in many different ways, but the 

 great systems of mountains are the result of warpings and foldings 

 of the earth's crust. These will be studied later. 



Habitability. Because of their low temperature, their steep 

 slopes, and their scanty soil, many mountains are ill-adapted to 

 farming purposes. The valleys of mountain regions are, however, 

 often fertile. Since transportation in mountains is difficult, they 



RELIEF MAP 

 CALIFORNIA 



Fig. 9. Topographic map of California. The state is largely mountainous, 

 but the central plain is conspicuous. 



are ill-adapted to most industries which depend on easy transpor- 

 tation. The most distinctive industry of mountains is mining; yet 

 many mountains have no ores or mineral matter of commercial 

 value, while many ores, and many mineral substances which are not 

 ores, are mined in plains and plateaus. 



Mountains in history. Mountains have played an important 

 part in history, partly because they are formidable barriers. They 

 have sheltered their inhabitants from invasion, and they have 



