102 THE GLACIAL LAKE AGASSIZ. 



by the chain of great hikes from Ontario to Superior, the west end of which 

 is close to the east border of the submerg-ed beh. At that time, and 

 onward through the Tertiary era, mucli of this eastern land area appears 

 to have been elevated at least several hundred feet above its present level, 

 so that streams eroded the deep basins which are now occupied by these 

 lakes, but then had a continuous westward descent. It seems probable 

 also that other great tributaries may have flowed westward and southward 

 into the Cretaceous sea, Ijringing sediments eroded from the areas of Hud- 

 son Bay, Lake Athabasca, and Great Slave and Great Bear lakes. The 

 absence of Mesozoic and Tertiary formations on the east border of the con- 

 tinent north of the southern coast of New England shows that from the 

 Gulf of Maine to Labrador and Hudson Bay the laud during these eras 

 stood higher above the sea-level than now. So long-continued high eleva- 

 tion, probably culminating at the beginning of the Glacial period, enabled 

 streams to erode the fjords of Maine, Newfoundland, and Labrador, the 

 gulf and estuary of the St. Lawrence, the deep channel of the Saguenay, 

 and the broad straits and bays dividing the lands of the Arctic archipelago 

 and separating them from Greenland. 



DENUDATION OF THE CRETACEOUS AREA. 



EROSION OF THE PLAINS TO A BASELEVEL. 



Rains, rills and rivulets, creeks and rivers have been slowly but con- 

 stantly wearing away the Cretaceous formations since their elevation above 

 the sea and the drainage of the immense Laramie lake, which for a long 

 period covered much of their area. When these marine and lacustrine 

 deposits were first raised to be dry land, they had a monotonously flat sur- 

 face; and they probably extended east, as we have seen, over the entire 

 basin of the Red River of the North and of the great lakes of Manitoba, 

 from which they now reach to the Rocky Mountains. The greater part of 

 the present Cretaceous area, though eroded far below its original surface, 

 is flat, undulating, or only moderately rolling, and conet'+utes a broad 

 expanse of plains with very slow ascent westward. But here and there 

 isolated areas of much higher hilly land, as the Turtle Mountain, consist of 

 reimiants of horizontal Cretaceous strata which elsewhere have suffered 



