126 THE GLACIAL LAKE AGASSIZ. 



ice-slieets of Scandinavia and Scotland were Ijeing- accumulated these coun- 

 tries stood far above their present height, the maximum uplift Ijeing- at least 

 equal to 4,080 feet, which is the depth of Sogne Fjord, the longest and 

 deepest fjord of Norway.^ 



At the end of the Glacial period, however, the glaciated regions are 

 known to have been mostly depressed somewhat below their present level. 

 This change seems to be well accounted for by the vast weight of the ice- 

 sheet itself, causing the land to sink finally beneath its load; and the 

 subsequent rise of the land is an expression of the buoyancy of the earth's 

 crust when it had been relieved by the disappearance of the ice. The pre- 

 glacial elevation may well have produced a cool climate throughout the 

 year, with abundant snowfall and resulting ice accunmlation; and the sub- 

 sidence of the burdened land would cause rapid melting of the ice upon its 

 borders and thence backward progressively over its whole area. 



EECESSIOTs^ OF THE ICE-SHEET. 



During- the departure of the ice its melting was due to the influence 

 of sunshine and rains, the latter being doubtless brought then, as now, by 

 great storms sweeping across tlie continent in an eastward and northeast- 

 ward course. In consequence, the borders of the ice-sheet appear to have 

 been pushed back generally in the same northeastward direction, beginning 

 on the west in the region of the Missouri and upper Mississippi rivers and 

 of the Red River of the North, and yielding successively or almost con- 

 temporaneously the region of the Laurentian lakes. New England, and the 

 eastern provinces of Canada.' Thus Lake Agassiz was formed in the Red 

 River Valley, and the basins of the Lam'entian lakes became filled by 

 glacial lakes outflowing soutliwestward to the Mississippi, until the outlet 

 from Lake Ontario by the Mohawk and Hudson rivers was uncovered from 

 the ice. Along the valley of the St. Lawrence the glacial current, which 

 had before passed southeast transversely across it to the coast of New 

 England, was, during this recession of the border of the ice-sheet, deflected 

 toward the southwest, conforming to the laAV that the glacial motion near 

 the edge of the ice turned perpendicularly toward its boundary. 



'Geol. Magazine (3), Vol. VIII, pp. 387-392, Sept., 1891. 



^Compare Proc, A. A. A. S., Vol. XXXII, 1883, pp. 231-234 ; and Geology of Minnesota, Vol. I, p. 641. 



