THE GREAT RELIEF FEATURES OF THE LAND 281 



Certain mountains with the general structure of laccoliths 

 for example, the Adirondack Mountains are not due 

 directly to the intrusion and doming effect of their igneous 

 cores. The original mountains formed by the intrusions were 

 worn away in former 

 cycles of erosion. The 

 present mountains are 

 residuals of strong 

 rocks left standing by 

 the removal of the 

 surrounding weaker 

 rocks. 



Mountains of un- 

 equal erosion. As 

 already indicated, 

 many mountains owe 

 their existence simply 

 to the superior resist- 

 ance of their rocks, 

 which have remained 

 in bold relief after the 

 removal of the sur- 



FIG. 295. A peak in the Wasatch Mountains, 

 with large accumulations of talus about its 

 base. (R. T. Chamberlin.) 



rounding softer rocks, or to a favorable position among 

 drainage lines. Such mountains are sometimes called moun- 

 tains of tircumerosion or circumdenudation. Most mountain 

 peaks (aside from volcanic peaks) are of this origin (Fig. 295). 

 Pikes Peak, Colorado, and Mt. Mitchell, North Carolina, the 

 highest peak in the Appalachian Mountains, are notable ex- 

 amples. The Catskill Mountains of southeastern New York 

 are really a dissected plateau. Any maturely dissected plateau 

 of considerable relief might similarly be called a group of 

 mountains (Fig. 296). 



Combination mountains. Folding and faulting, vulcan- 

 ism and unequal erosion, may all be concerned in the forma- 

 tion of lofty mountains. Many mountainous regions, fur- 

 thermore, have had several periods of growth, between 



