THE MAKING OF MOUNTAINS 41 



built up after the fashion of volcanoes, for example, 

 neither do they owe their existence directly to deforma- 

 tion of the crust. On the contrary, their most char- 

 acteristic representatives are remnants of formerly 

 more or less extensive high grounds or plateaus of one 

 kind or another. The strata with which they were once 

 continuous have been gradually reduced and removed 

 by surface weathering. Relict mountains are thus 

 monuments of erosion; they have been carved out of 

 rock masses, the geological structure of which varies 

 indefinitely, but rarely coincides with the outline of the 

 ground." 



Let us follow Professor Geikie farther. An Original 

 or Tectonic mountain may be eroded down to its roots, 

 to its base-level. In this way an undulating plain 

 a plain of erosion comes to replace the vanished 

 mountain. If the plain is gradually uplifted again it 

 becomes a plateau of erosion. Or if the plain is sub- 

 merged beneath the sea and sediment accumulates 

 upon it in the form of gravel, sand, or mud, and if the 

 drowned and buried plain be bulged up again, it be- 

 comes a plateau of accumulation. If the erosion of 

 the Original or Tectonic mountain was not so 

 thoroughgoing as we supposed there might be (after 

 re-elevation) a plateau of erosion with a more or less 

 irregular surface, or a plateau of accumulation the 

 lowest parts of which showed the irregular stumps or 

 roots of the Original mountain, while the upper parts 

 consisted of more or less horizontal beds of sedimen- 

 tary rock. 



Now the point is, that Relict or Residual mountains 

 may be carved out of a plateau of accumulation, out 

 of an accumulation tableland, and such mountains are 



