256 R. S. TARR — FORMER EXTENSION OF CORNELL GLACIER. 



and distinctly above the currents caused by the topographic irregularities, 

 would be extensively worn. 



Extension of the Ice over the Upper Nugsuak Peninsula. 

 topography of the upper nugsuak. 



This peninsula, which was made the base of our studies, is the longest 

 arm of the land extending from this part of the Greenland coast. It 

 stretches about southwest from the general coastline, and hence is not 

 quite normal to its average course, which in this region is about north 

 15 to 20 degrees west (true north). From the ice-cap at the base to the 

 extreme end of the Upper Nugsuak peninsula to Wilcox Head the dis- 

 tance is from 23 to 25 miles, and 8 or 10 miles farther, in the same line, 

 are the Duck islands. Hence we have here a land area reaching to a 

 distance of 30 or 35 miles from the present ice-margin The width of 

 this land is nowhere more than 4 or 5 miles, and generally is only 2 or 3- 



The elevation of the peninsula varies up to 2,900 feet, and there are 

 many peaks reaching to heights between 1,000 and 2,500 feet. The to- 

 pography is extremely rugged. It is evident that the narrow peninsula 

 is a preglacial divide, and it is crossed by deep valle3 7 s, which often 

 end in bays and fiords. These valleys extend across the peninsula, 

 and in some cases have been perceptibly smoothed and grooved by 

 glacial erosion. They have the appearance of mountainous valleys 

 which have passed the stage of early youth, but were still young or ado- 

 lescent when submergence transformed their mouths to fiords. This 

 ruggedness of preglacial origin is increased by the effects of marked post- 

 glacial denudation. The hill tops and sides have been gullied by the 

 mountain torrents, furnished with floods of water when the snow melts 

 before the rising summer sun, and the valley sides and hill slopes have 

 been encumbered with extensive talus accumulations of frost-riven boul- 

 ders of great and small size. So rugged is the country from this cause 

 that our average rate of progress over its surface on foot probably did not 

 exceed one mile an hour. 



The rocks are of metamorphic origin, and from a field study appear to 

 have been derived from a sedimentary series. This has been intricately 

 folded and faulted.* Among the rocks there is much variation in tex- 

 ture and in resistance to denudation, and hence the topography is often 

 nearly related to the rock structure and position. This is especially well 

 shown where trap dikes cross the metamorphic series, for their position 

 is almost invariably marked by valleys. No sedimentary strata were 



* The bed-rock geology was studied by Professor Gill, and he will publish his results after study- 

 ing the thin-sections of rock. 



