SELUDIES OF THE CYCLE OF GLACIATION 379 
II. THE TRANSITIONS BETWEEN THE MOUNTAIN 
GLACIER AND THE ICE CAP 
_ From the standpoint of the sculpturing of the lithosphere, the 
ice cap is sharply set off from all types of mountain glacier through 
its inability to accomplish a sapping of rock surfaces due to rapid 
frost-weathering. Its sculpturing processes are therefore restricted 
to plucking, abrasion, and to a very limited extent frost-weathering 
on flattish surfaces—processes which in combination leave the 
rock rounded and presenting surfaces which are flatly convex 
ogo 
Fic. 11.—View of terraced cirque above Lake Grinnell, Glacier National Park 
skyward. ‘That these processes combined play but a subordinate 
role to frost-weathering in the case of all the types of mountain 
glaciers, would seem to be sufficiently attested by the sharply 
accented features which are brought about with their concavities 
toward the sky." 
Since the mountain glacier owes its very existence to a rock 
container within the lithosphere surface, the inclosing rock walls 
t Hobbs, Earth Features, etc. (1911), p. 379, Fig. 405. 
