GEOLOGY: W. E. EKBLAW 
291 
Mr. Eakin that I merely call attention to this phase dependent upon the 
melting of the dome-shaped drifts. 
The piedmont drifts formed on the lee slopes, or at the foot of the lee 
cliffs, act somewhat differently. The melting edges are at the top of the drift, 
and at the bottom. At the top the process is a sapping one, cutting back the 
cliff; at the bottom solhiuction is the dominant process, though generally 
there is also some direct transportation by excess surface water that does not 
seep through the soil. The drift melts down from the top, and back from the 
foot. F. E. Mathes, 2 in his discussion of the glacial sculpture of the Bighorn 
Mountains, illustrates a cross section of such a drift, and the direction of the 
erosive attack upon the cliff. From the lower edge of the cliff where soli- 
fluction begins, the movement of the soil may continue to the foot of the slope, 
in one continuous sheet, or it may progress in a series of steplike slopes, or 
sloping terraces, with crescentic terminal margins, like festoons. Throughout 
northern Greenland these piedmont drifts are numerous, and almost invari- 
ably they give rise to similar solirluction slopes. When they occur on both 
sides of a V-shaped valley they tend to grade the sides and build up the 
bottom until it becomes U-shaped, as Mathes has described. 
The wedge drifts formed in gullies and small gorges near the tops of cliffs, 
while acting in the same way as the piedmont drifts, produce different re- 
sults. When these wedge drifts melt, the sapping process mentioned in the 
piedmont drifts cuts back the sides and the head of the gully or gorge in 
such a way as gradually to give it the form of a segment of a circle, the depth 
and extent of the segment depending upon the amount of snow blown into it. 
In this way a typical cirque may be initiated. When the snowdrifts become 
so large that they do not melt during the summer, ice gradually forms and a 
glacier occupies the floor of the cirque; frequently, though, the snow all melts 
away during the summer and no ice is formed, yet the cirque-form continues 
and the process goes on. A cirque in which ice has played no part can usu- 
ally be distinguished by its rough and uneven floor, not at all like the scoured 
floor of a cirque once containing a glacier. The bergshrund in these high 
latitudes does not play an important part in cirque formationas it 
apparently does farther south, even in those cirques in which glaciers are 
formed; in the cirques carved by nivation alone there is, of course, no 
bergshrund at all. 
Nivation is unquestionably of prime importance in the development of 
some of the topographic forms of the Greenland coast, and plays no small 
part in the degradation of the high cliffs, and the grading of the slopes. 
Solirluction as defined by J. G. Andersson 3 is the process by which masses 
of the regolith saturated with water (which may come from melting snow or 
rain), flow slowly from higher to lower ground. This saturated, semi-fluid 
substance, not at all assorted as to size of fragments, moves along in much 
the same way as a glacier. H. M. Eakin 1 defined the process of solifluction 
as the migration of detritus under the thrust and heave of frost action. He 
