DEPTHS OF FJORDS. 199 



at least several thousand feet above their present altitudes. These 

 epeirogenic movements of uplift, suggested by the ice-sheet of Green- 

 land, I believe to have been the cause of the climatic changes by which 

 the ice-sheets of North America and Europe were accumulated. 



The depth of the fjords and now submarine valleys on the coasts of 

 the northern half of our continent indicate that the borders of our glaci- 

 ated area were mostly uplifted 2,000 to 3,000 feet, and the preglacial ele- 

 vation of the central parts of Canada was probably 5,000 feet or more, 

 giving the necessary slope for the outflow of the ice-sheet, excepting so 

 far as that outflow was due to the thickness of the ice. The same argu- 

 ments for high preglacial altitude of Scandinavia have been recently well 

 stated by Mr T. F. Jamieson, who notes the depth of the Christiania 

 fjord as 1,380 feet, of the Hardanger fjord, 2,624 feet, and of Sogne fjord, 

 the longest in Norway, 4,080 feet.* 



Probable Rates of Erosion by Pleistocene Ice-sheets. — The Muir glacier is 

 found to be eroding its rock bed at the rate of about three-fourths of an 

 inch yearly, or one foot in sixteen years, and six feet in a century. 

 Doubtless the erosion by the ice-sheets of the glacial period was equally 

 rapid in the zone of most efficient action, which may have been usually 

 from 50 to 200 miles inside the ice boundary. In 1,000 years this zone 

 would be eroded to an average depth of 40 feet, and in 5,000 years 200 

 feet. Farther within the ice-covered area the erosion was probably some- 

 what less, but during the recession of the ice-sheet, and perhaps also dur- 

 ing its accumulation, the maximum rate of erosion would prevail succes- 

 sively upon all parts of the drift-bearing regions. In the light of this 

 comparison with the modern Muir glacier, it is evident, from the volume 

 of the drift and the topographic features of the country, that a geologic- 

 ally brief period, at the longest perhaps 10,000 or 20,000 years, would 

 suffice for the observed volume of the Pleistocene glacial erosion and re- 

 sulting drift. 



Subglacial and englaciat Transportation of Drift. — Under this heading an 

 ample discussion would require much space. It may be therefore suf- 

 ficient to state that the observations of the inland ice of Greenland by 

 Hoist and of the Malaspina glacier by Russell, reaffirming the conclu- 

 sions reached through investigations of the North American drift by 

 Dana, Shaler, C. H. Hitchcock, N. H. Winchell and others, including 

 myself, seem to me to prove undeniably that the Pleistocene ice-sheets 

 contained much drift in their lower portions to heights of probably 1,000 

 to 1,500 feet above the ground. This transportation of drift within the 

 ice seems to me to have been equally important, and almost equal in 

 amount, with the subglacial transportation. Professor James Geikie, 



*Geol. Mag., Ill, vol. viii, pp. 387-392, September, 1891. 

 XXX— Bull. Gkol. Soc. Am., Vol 4, 1892. 



