- Mountain peaks in Teton Range, Wyoming. 
306 ELEMENTARY GEOLOGY 
Since its main characteristics are unusual elevation, 
and a more or less conical form, and since the present 
height and outline are largely due to the fact that the 
peak has better resisted the action of denudation than 
has the neighboring land, it seems fair to include 
among mountain peaks any unusual elevation, of a 
somewhat conical form, which has resisted denudation. 
So, therefore, the buttes 
or hills of circumdenu- 
dation (Fig. 180) (the 
hills which have been 
left because denudation 
has cut the rock mate- 
rial away from them on 
all sides) of the western 
plains, may properly be 
called mountain peaks. 
Fic. 179. 
It is also customary to 
class volcanic cones as mountain peaks, but although 
this is certainly defensible, these are such typical 
geographic forms, that it is well to give them a 
separate name. 
Not only may individual peaks result from greater 
durability of certain classes of rocks, but great groups 
of peaks may be formed in the same way. For 
instance, this is particularly the case in the Catskills, 
which are not folded into anticlines and synclines, as 
