THE GLACIAL LAKES 



Eric and the other in the Huron basin. As the ice retreated 

 Lake Arkona tell to lower levels, building beaches at each halt 

 in the lowering process, and the outlet continued through 

 Grand River to Lake Chicago. 



Expanding Lake Chicago 



As Lake Chicago continued to receive the discharge through 

 Grand River from Lake Saginaw and Lake Arkona, the lake 

 increased in size, particularly to the eastward, so that the 

 river entered it near Grand Rapids, rather than near the 

 Indiana line as at the earlier stage. During the retreat of the 

 Lake Michigan ice lobe the crescent-shaped lake had developed 

 several large bays along its eastern border, near the present 

 mouth of St. Joseph River, along the lower course of Kalama- 

 zoo River, and in the region west of Grand Rapids. The St. 

 Joseph, Kalamazoo, and Grand rivers abandoned their former 

 united course to the Kankakee, past South Bend, Indiana, and 

 each, in the order named, became an independent stream en- 

 tering a bay of Lake Chicago. 



Restored Lake Saginaw; Lake Newberry 

 Then the ice made a powerful and rapid re-advance south- 

 ward. It cut off the waters in the Saginaw area and restored 

 Lake Saginaw to independence, but did not change its level 

 or its outlet to Grand River. It cut off the waters in the 

 Finger Lakes region of New York, to form independent Lake 

 Newberry, and caused them to find an outlet through Lake 

 Seneca and Susquehanna River. (Figure 8.) We know that 

 it was a re-advance of the ice which caused these changes, be- 

 cause the high Port Huron moraine — built when the glacier 

 halted — covers part of the Arkona beaches. As we trace the 

 Arkona beaches we find them suddenly disappearing under 

 the Port Huron moraine, south of Cass City, Michigan, but 

 they re-appear at the same level farther north in the Thumb 

 area and thus very evidently are buried under the mor.iine in 

 the intervening miles, 



4) 



