424 M. JEFFERSON GLACIAL EROSION IN THE NORTHFIORD 



into a pit on the mountain side, whence flows the stream that has built 

 the huge fan of excavated material on the shore of the lake; the lower 

 caps the fan with snow-ice from the cone above. The falling of water 

 has doubtless aided here in digging the pit. All along Stryn lake bot- 

 ners are seen; all along the Northfiord they are sighted, not remnants of 

 valley glaciers, but pockets of ice eating their way into the mountain. 



Origin of Botner-like Fiord Heads 



The fiord heads themselves, in which lie the great ice-tongues from the 

 Jostedal glacier, head up in the same amphitheater form. Plate 42 shows 

 [sic] this for the Brixdalsbrae ; Kjendals, Kvandals, and the Maelke- 

 voldsbraes show the same thing. . The headward branches of the North- 

 fiord are three or four thousand feet deep within a mile or two of the 

 great ice sheet on the plateau. It is difficult to think of the erosion of a 

 sixty-mile-long canyon by a plucking, grinding ice stream in this extra- 

 ordinary form, almost equally deep from mouth to source. The width 

 has diminished by a half or two-thirds from sea to head, the depth but a 

 fourth to a third. 



Kichter (1896) has pointed out that the process of carving the great 

 fiords is quite different from that by which Alpine valleys have been 

 made, and refers most of their excavation to the interglacial periods. 

 The ice river below carried off the fragments that frost and other stib- 

 aerial agents strip from the walling cliff, and a stagnating ice sheet above 

 mainly served to protect the plateau surface from erosion. These were 

 the agents at work when the ice was diminishing after a period of in- 

 tense glaciation. These conditions are still present at the fiord heads. 

 The material excavated here is sufficient to make a flat filling that floors 

 the head of the valley to unknown depths — spread out thus in the enor- 

 mous volumes of water that issue from the melting ice. 



Erosion on Lofjeld 



Some notion of the style of erosion that is going on beneath the ice- 

 sheet may be had by examining lower border parts of the upland from 

 which the ice has now withdrawn. The only place at which this was 

 done was the mountain top that overhangs Loen, the Lofjeld, the part of 

 the Skaala outlier of the Jostedalsbrae that lies west of the Tjugedal. 

 It is now bare of ice except in a few sheltered spots. It has a rounding 

 summit at 3,800 feet. The crest is of ledges of gneiss, glaciated from 

 south 70 degrees east to north 70 degrees west. This comes out in 

 rounded lee-and-stoss forms. The motion was parallel to the fiord. No 



