QUATERNARY 



653 



Lake Maumee) came into existence near the western end of what is 

 now Lake Erie, and which emptied through the Wabash River into 

 the Mississippi River. This may, for convenience, be called the 

 first stage (Fig. 568) in the history. In the second stage, the ice 

 front had retreated to such an extent that a greatly expanded Lake 

 Erie (glacial Lake Warren) was formed which emptied through 

 the Illinois River into the Mississippi River. Upon a further retreat 

 of the ice, a third stage (Fig. 569) was inaugurated, with the resulting 



Fig. 569. — A {third) stage, in which three Great Lakes with separate outlets were 

 formed by the further retreat of the ice front. (After Taylor and Leverett.) 



formation of three Great Lakes with three outlets ; Lake Superior 

 (glacial Lake Duluth) discharging over the divide at Duluth through 

 the St. Croix into the Mississippi River, Lake Michigan (glacial Lake 

 Chicago) through the Illinois River as before, and lakes Erie and 

 Huron (glacial Lake Lundy) through the Mohawk River in New 

 York to the Hudson River. In the fourth stage (Fig. 570) the 

 region of the Great Lakes was entirely uncovered with the exception 

 of the St. Lawrence River ; at this time the present lakes Michigan, 

 Superior, and Huron were greatly expanded to form a lake which 

 covered a greater area than that occupied by all of the present Great 

 Lakes. This lake (named Lake Algonquin) discharged through the 

 Mohawk River to the Hudson and probably also for a time through 



