422 M. JEFFERSON GLACIAL EROSION IN THE NORTHFIORD 



The Skaala glaciers, facing northward, reach down below 4,500 feet. 

 Above 4,000 feet water rarely runs. A little patch of snow lay at the 

 back of this second botner, behind the lakelet of its rock basin, but is 

 probably not perennial. This botner is the bowl of little Skaala through 

 which the ascent to the crest of the mountain is made. Most of its floor 

 is occupied by an extensive field of broken stones, naked and somewhat 

 weather stained, under which water is heard running. This is in part 

 frost-shattered ledge, in part moraine from another botner that opens 

 into it behind and above. There is no moraine at the botner mouth, nor 

 resting place for it short of the valley floor, 1,500 feet below. 



Over across the Tjugedal valley, on the northern border of the snow- 

 field that lies near its head, an abundant talus of fine rocky fragments 

 rests against a strong, firm clifl: of gneiss. From below one sees nothing 

 but bare clifi^ above, but from the opposite crest of Skaala two botner 

 glaciers are seen to lie just over the shoulder of the valley wall. The 

 Skaala botners would probably overhang the valley by several hundred 

 feet if the ice were out of them, as the two on the north side are over 

 1,000 feet up and the little Skaala a good 1,500, having been excavated 

 probably when the snowline lay 600 or 700 feet lower than now. Here, 

 then, are hanging valleys that have originated by excavation at various 

 times and heights in the walls of a valley already excavated. 



HEADWARD EROSION OF HANGINO VALLEYS 



Tjugedal itself can hardly have any other explanation. It is not the 

 valley through which a snowfield drained. There is no snowfield at its 

 head. Like the Praestedal, it heads against a thin wall of rock that 

 alone separates it from the deep valley of Stryn. The snow and ice that 

 passed through it have always been what fell within its walls. Some ice 

 'may have cascaded into it once by. the valleys of little Skaala, but this 

 entered near the mouth, and can not have helped greatly in the excava- 

 tion of the valley, and it is likely that at the time the snowline was low 

 enough to fill the main valley with ice the stepped botner valleys in the 

 sides of Tjugedal were not yet existent. 



It is not inconceivable that some weakness of rock structure may have 

 guided headward erosion along it while the snowline was rising from the 

 1,800-foot level represented at the mouth to the 3,500 one at the head 

 wall by the process of sapping at the contact of ice and rock in the zone 

 of constant freezing and thawing. Such a process should cause a botner 

 to widen as well as deepen, as each wall should recede, and this process 

 is at work on the Norwegian plateau today, reducing every summit that 

 projects above the general level, as Eichter has pointed out. The Skaala 



