426 M. JEFFERSON GLACIAL EROSION IN THE NORTHFIORD 



gen has 70 inches of rain, but has known no temperature under 5 degrees 

 Fahrenheit, and sheer cliffs of gneiss there, as on the face of Blaamanden 

 1,000 feet above the city and fully exposed to the Atlantic winds, stand 

 almost without talus at their foot, with hardly a scar on the purple 

 weathered rock. 



Unweathered Detrirus 



The most striking evidence of the high erosive activity of the ISTor- 

 wegian streams is the fresh, light-colored detritus that they handle. The 

 Northfiord gneisses weather to a dull purplish red, being light gray when 

 fresh. Many of the side tributary streams, like the Tjugevoss, carry 

 only gray boulders, pebbles, and sand in their bed. As I have already 

 stated, only fresh unweathered rock is seen, either as ledge or detritus 

 for a mile or two from the glaciers at the heads of the fiord. Above the 

 snowline the frost-shattered blocks are not thus fresh. Discolored fel- 

 spars, with pink and reddish tints, are characteristic, attesting a long 

 stay on that spot. 



" Conclusions 



I saw in the Northfiord moderate evidence of a glacier's power to grind 

 its bed of rock with rock fragments for tools, some hanging valleys that 

 may be the work of tributary valleys, as in the current explanation ; more 

 that seemed due to the enormous headward erosion of botner glaciers 

 near the snowline; great activity of frost at all levels away from the 

 coast and of running water below four or five thousand feet above the 

 sea, operating to carry rock waste seaward so rapidly that it had little 

 chance to weather during the trip. 



References 



1879. Albeecht Penck : Die Gletscher Norwegens. Mittheilungen des Vereins 



fiir Erdkunde zu Leipzig, p. 11. 

 1887. Israel Cook Russell : Quaternary history of Mono valley, California, in 



Eighth Annual Report, Director U. S. Geological Survey, p. 353. 

 1896. Edward Richter: Geomorphologische Beobachtungen aus Norwegen. 



Sitzungsberichte der Kaiserlicheu Akademie der Wissenschaften, math- 



ematisch-uaturwissenschaftliche Classe, Band CV, Abtheilung I, 1896, 



p. 179. 

 1902. Carl Feed. Kolderup : Fjeldbygningen og Bergarterne ved Bergen. Ber- 



gens, Museum, Aarbog, 1902, no. 10, map. 



