QUATERNARY 655 



the old Chicago outlet. During an early part of the stage Lake Huron 

 probably emptied into Lake Erie, but later, when the ice front had 

 melted back farther to the north, drained through the Trent River in 

 Canada to Lake Ontario (named Lake Iroquois), reducing Lake Erie to 

 such an extent that the amount of water flowing over Niagara falls was 

 probably not greater than that now pouring over the American falls. 

 As the land was uplifted in the north (as the weight of the ice was re- 

 moved), the drainage of Lake Huron was again discharged over 

 Niagara Falls. The fifth stage (Fig. 571) began with the opening of 

 an eastern passage along the ice border into the Ottawa valley, which 

 lowered the surface of the lakes (forming Lake Nipissing). The 

 drainage passed through this outlet until the elevation of the land 

 on the north was sufficient to send the waters into their present course. 

 The beach lines of this fifth stage rise at the north (are higher at the 

 north than at the south), showing an uplift of 100 feet at the head of 

 the Ottawa River since it was abandoned. 



There seems little doubt that at each advance and retreat of the 

 ice, during the different stages, lakes were formed in somewhat the 

 same position as at the close of the last ice (Wisconsin) invasion. 

 The proof of such, lakes is not abundant, but is indicated by the 

 sandy character of the drift in the moraines at the south end of Lake 

 Michigan, the sand having probably been obtained by the ice from 

 the deposits of a former Lake Michigan. 



REFERENCES OX THE HISTORY OF THE GREAT LAKES 



Chamberlin and Salisbury, — Geology, Vol. 3. 

 Tarr, R. S., — Physical Geography of New York State. 



Taylor, F. B., — The Glacial and Postglacial Lakes of the Great Lake Region: Smith- 

 sonian Rept., 1912, pp. 291-327. 



The Champlain Subsidence. — The fifth stage (Fig. 571) of the 

 Great Lakes was coincident with a great subsidence of the north- 

 eastern Atlantic coast, which permitted the sea to spread over the 

 St. Lawrence valley, Lake Ontario, Lake Champlain, and the Hudson 

 River, thus making New England an island. 



The sediments carried into these bodies of water at that time contain 

 marine shells and even the skeletons of whales, one of which was found 

 in a Lake Champlain terrace, and another in the Ottawa valley. 

 The terraces near Montreal which are 600 feet above the sea, those of 

 Lake Champlain which are 500 feet at the northern end and 400 feet 

 cleland geol. — 42 



