90 
EXPLORATIONS IN TURKESTAN. 
The crest lines of the nonnally carved mature ridges are rather sharp and 
somewhat serrate. The slight convexity of the slope lines as they reach the crest 
shows that those processes of weathering in which changes of volume act nearly 
nonnally outwards from the weathered surface there have a relati\-el}- large share, 
along with gravitative down-slope washing, in the reduction of the mountain mass. 
This systematic coml)ination of nonnally eroded fonns was seen not only 
about Kugart pass, but in various other ranges, and in var)'ing degrees of develop- 
ment; but many of the liigher ranges exhibited fonns of another kind, imposed, 
as it were, upon the nonnal fonns of the valley heads ; and as these additional 
fonns were, in all cases where they could be closely examined, sj'stematically asso- 
ciated with moraines, they may at once be ascribed to glacial erosion and called 
glacial fonns. The glacial fonns are no novelty ; they are well known in other 
mountains. They are described here merely to show how systematically they 
repeat the features of similar fonns seen elsewhere. Their most significant features 
are as follows : They occur at great altitudes, such as 8,000 feet, in ranges that 
rise to still greater altitudes, such 
as 12,000 feet or more. They are 
independent of rock structures. 
When considered in profile they 
involve a double change of slope 
from that of nonnal fonns. If 
ABC (fig 53) represents a nor- 
mal slope, a glaciated slope, DEB, 
is steeper than nonnal in the 
upper part, D E, and less steep 
than normal in the lower part, 
E B. The steeper upper slope, 
D E, may be sunnounted by a less steep slope, A D, or it may rise directly to the 
crest line. When two such slopes meet, back to back, the crest is an unusually 
sharp and serrate arete. The lower slope, E B, may be hollowed to a basin form. 
When considered in plan, the glacial forms are simpler than the nonnal fonns 
that they have replaced, for they involve 
the substitution of a single broad-floored 
concave fonn for a number of inter- 
locking ravines and spurs. When two 
simple fonns of this kind are associated, 
the smaller one may open its floor in 
the wall of the larger one, so that the 
two floors do not join at accordant grade. 
Glaciated valle}' heads are so well defined that they have received a special name 
from mountaineers in different countries — cirque and kar in the Alps, botn in 
Norway, rMm in Wales, corrie in Scotland. All these features have been abundantly 
described by various writers — Bohm, Richter, De Martonne, Marker, Johnson, 
Gannett, Gilbert, L,awson, to name no more. 
Fig. 53. — Profile of a Cirque at the Head of a nonnal Valley. 
Fig. 54.— Cirque in the Kalkagar-tau. 
