STUDIES OF THE CYCLE OF GLACIATION 375 
gently sloping summit plane of Quadrant Mountain in the Yellow- 
stone National Park at an elevation of between 9,000 and 10,000 
feet' (Fig. 9), since Antler Peak and Bannock Peak guard the 
entrance to the cirque. 
It is especially because the comb ridges in the highest levels 
are precipitous and correspondingly thin that a continuation of 
Fic. 7—Gunsight Pass, seen from Gunsight Chalets looking across Gunsight 
Lake, Glacier National Park. 
the process removes their pinnacles while the broader ridges some- 
what farther out and just below the mother-cirques are being 
sharpened into peaks, both alike through sapping from the cirques. 
To bring together the extremes of mountain glacier erosion 
which are represented by the Bighorn Range and the Glacier 
National Park with the intermediate stages which connect them, 
the four generalized plans of Figure 1o have been prepared. In 
order, these are: 
T. The youthful channeled or grooved upland 
II. The adolescent early fretted upland 
III. The fretted upland of full maturity 
IV. The monumented upland of old age 
“The Cycle of Mountain Glaciation,” Geogr. Jour., Vol. XXXVI (1910), 
Figs. 8, 14. 
