THE GREAT RELIEF FEATURES OF THE LAND 275 



Compared with the diameter of the earth, even the loftiest 

 mountains are insignificant protrusions of the lithosphere. 



Mountain ridges and peaks are grouped commonly in 

 relatively long and narrow belts, called mountain ranges. 

 When several more or less parallel ranges are grouped to- 

 gether, they constitute a mountain system. Thus, one speaks 

 of the Wasatch Range of Utah, but of the Rocky Mountain 

 System. 



Distribution of mountains. It is noteworthy that moun- 

 tain ranges are situated in general near the edges, rather 

 than in the interiors, of the land masses. It is striking, also, 



FIG. 287. Mountains rising conspicuously above an aggraded plain. 

 Alaska. (Netland, U.S. Boundary Commission.) 



that most of the loftiest mountain chains are not far from 

 the shores of the greatest sea, the Pacific Ocean. In a general 

 sense, the land masses accordingly have two very unequal 

 slopes, a short and relatively steep one toward the Indian- 

 Pacific, a long and gentle one toward the Atlantic or Arctic 

 Ocean. What is most significant probably is that most 

 mountain chains are near the junctions of the continental 

 plateaus and the ocean basins, and that most of the longest 

 and highest ones are near the edges of the greatest basin. 

 The settling of the larger and heavier ocean basins, due to 

 the cooling and consequent contraction of the earth, possibly 

 may have been an important cause of the deformation of the 



