BEACHES OF LAKE MALIMEE. 739 



VARIATIONS IN ALTITUDE. 



There appears to have been very Httle warping- of the south shore of 

 Lake Maumee west of the Ohio-Pennsylvania line. The slight variations 

 displayed by each of its beaches are no g-reater than may be found along 

 the present shore of Lake Erie; but near the Ohio-Pennsylvania line a 

 differential uplift had caused the beaches to increase perceptibly in altitude 

 in passing- eastward. This, however, affects only the second beach of Lake 

 Maumee, and that for but a few miles. The discussion of the uplift may 

 therefore be taken up to better advantage in connection with the beaches of 

 Lake Whittlesey and Lake Warren. 



The upper beach of Lake Maumee stands about 775 to 785 feet above 

 tide throughout its course from Fort Wayne to Cleveland. The second 

 beach stands about 765 feet above tide in the same interval, but rises about 

 10 feet between Cleveland and the Ohio-Pennsylvania line, and attains near 

 its terminus in northwestern Pennsylvania an altitude of about 780 feet. 



RELATION TO THE ICE SHEET. 



The dvdndling and disappearance, of the beaches of Lake Maumee in 

 passing from northeastern Ohio into northwestern Pennsylvania, taken in 

 connection with the fact that the ice sheet withdrew in that direction, makes 

 it practically certain that the eastern limits of the lake were determined by 

 the ice sheet. It appears, also, that the presence of the ice sheet in the low 

 places on the rim of the Erie-Huron basin in Michigan and' of the Ontario 

 basin in New York caused the lake to rise to the Fort Wayne and Imlay 

 outlets. The withdrawal of the ice sheet from these low places, as indicated 

 farther on, brought them into use as outlets and thus allowed the lake level 

 to become lower. It is probable, also, that the Lake Escarpment morainic 

 system was in process of formation during most of the time that Lake 

 Maumee stood at the level of the second beach, and that the Cleveland and 

 Defiance moraines were formed while it occupied the upper beach. 



The strength of the portion of the upper beach inside the Defiance 

 moraine is about as great on the south shore as the portion outside that 

 moraine; but on the west shore, as already indicated, the portion inside 

 the Defiance moraine is decidedly weaker than that outside. It is not 

 difficult to find an explanation for the strength of the portion of the south 

 shore inside the Defiance moraine. Much of this part of the shore fronts 



