1111. GLACIAL LAKES 



twenty to forty feet deep, leading from the present Lake 

 Gogebic to Presque Isle River, thence in a northward loop 

 almost to Lake Superior, thence westward again past Bes- 

 semer, Michigan, and Saxon, Wisconsin, into glacial Lake 

 Ashland in the norihwcsiern corner of Iron County, Wiscon- 

 sin, The ice border drainage from Baraga County eastward 

 drained southward into glacial Lake Chicago. The old beds of 

 glacial lakes Brule, Ashland and Ontonagon are the fertile 

 agricultural lands in an otherwise rocky infertile region. 



Lakl Warrln' 

 At length came another oscillation of the ice, and the east- 

 ern outlet for the lakes in the Huron-Erie basin was closed. 

 The lake waters again were raised above the level of Lake 

 Wayne and created the lake known as glacial Lake \\'\irren. 

 (Figure 9.) It was at the level of Lake Saginaw and once 

 more deprived that lake of its independence. But despite the 

 southward oscillation of the ice front which closed the east- 

 ern outlet, the ice had melted far enough north so that now 

 the lakes entered the Ontario basin. The outlet returned to 

 Grand River, and the waters from all the lakes, including the 

 waters of the Finger Lakes region of New York and of Lake 

 Simcoe in Ontario, drained to the enlarged Lake Chicago and 

 thence to the Des Plaines-Illinois, or Chicago, outlet to the 

 Mississippi. Lake Warren repeated the history of Lake Whit- 

 tlesey : it was the result of an ice advance, its waters were raised 

 above the level of its immediate predecessor lake, and its 

 violent storm waves tore into the material of the Lake Wayne 

 beaches to build its own strong, sandy and gravelly beaches, 

 which also have been used by men for travel routes. 



Laki: Dulu ih 



In the Superior basin the ice retreated step by step until the 



western end of the basin was uncovered. Lakes St. Louis and 



Nemadji drained into Lake Brule, and all became a part of 



Lake Duluth — the ancestral Lake Superior. This was a cres- 



47 



