362 
SUMMIT PLAIN OF ROCKIES 
patches of the sandstone which still persist on the back of the 
Cordillera, the two coincide. Moreover, it appears that the so- 
called Summit Plain is present chiefly only near the isolated tracts 
of the Dakotan sandstone. In some places it is seen to pass ben- 
neath the sandstone. 
Therefore, it seems very clear that the Summit Plain cannot 
possibly be the remnantal extension of any hypothetical surface 
the position of which was formerly high above the Great Plains 
to the eastward. Neither can it possibly be an uplifted part of 
the present surface of the Great Plains that has become separated 
by deformation and erosion. ,It is apparently a detached area 
of the old Comanchan peneplain, that has been recently exhumed 
through the peeling off of the protecting Dakotan sandstone. 
There is one thing for which the Front Range of the Rockies 
is especially notable in a literary way. It is made the theme of 
extended physiographic description in which geologic features 
and geologic terms have no essential part. Were it not for the 
fact that in this method of geographic treatment there lurks 
great inherent dangers of defective visualization of the true 
succession of events the plan might find wide application. By 
ignoring the geologic setting the Summit Plain becomes a section 
of the newest peneplain, whereas it really appears adjusted more 
properly to the oldest of the four peneplains of the region. It 
is an unearthed product of remote Comanchan times rather than 
a structure originating in the Recent epoch. With this con¬ 
clusion our ideas concerning the physiography of the entire 
Rocky Mountain region stands sorely in need of complete re¬ 
vision. 
