376 



EARTH FEATURES AND THEIR MEANING 



rock surface below from the jagged and precipitous one above 

 (Fig. 400). Inasmuch as this boundary usually separates the 

 scalable from the inaccessible slopes above, snow is apt to lodge 

 at this level and make it strikingly apparent. 



If uplift of the land occurs while glaciers occupy the valleys of 

 mountains, an increased capacity for deepening the valley is im- 

 parted to these ice 

 streams, ana We find, 

 as ag^g^feftti a deep 

 central valley "d'f U 

 cross section exca- 

 vated within a rela- 

 tively broad trough 

 visible above the 

 shoulder oneither side 

 of the later furrow. 

 Save only for its 

 characteristic curves, 

 such a valley bears 

 close resemblance to 

 a mature stream val- 

 ley which has been rejuvenated (see p. 173). The remnants of the 

 earlier glacier-carved valley are, as already stated, gently curving 

 high terraces so common in Switzerland, where they are known as 

 albs or high mountain meadows. These albs may be seen to special 

 advantage on the sides of the Chamonix valley (Fig. 401), the 

 Lauterbrunnen valley, or in fact almost any of the larger Alpine 

 valleys. 



The cascade stairway in glacier-carved valleys. If now, instead 

 of giving our attention to the cross section, we follow the course 

 of the valley that has been occupied by a glacier, we find that it 

 descends by a series of steps or terraces having many backwardly 

 directed treads (plate 19), whereas a normal and well-established 

 river valley has only forward grades. Because of these back- 

 ward grades the stream waters are impounded, and so lakes 

 are found strung along the valley in chains as the larger beads 

 are found in a rosary, and these are the characteristic rock basin 

 lakes sometimes referred to as "Paternoster Lakes" (see *p. 412 

 and Fig. 402). 



FIG. 401. View of the Vale of Chamonix from the 

 se'racs of the Glacier des Bossons. The alb of the 

 opposite side is well brought out. 



