Fig. 360.—Map to show the first stages of the ice-dammed lakes within the St. Lawrence basin (after Leverett and Taylor).
Within each of the Great Lake basins a crescentic lake early appeared at that end of the depression which was first uncovered by the glacier: Lake Duluth in the Superior basin, Lake Chicago in the Michigan basin, and Lake Maumee in the Huron-Erie basin ([Fig. 360]).
We may now, with profit, trace the successive episodes of the glacial lake history, considering for the earlier stages those changes which occurred within the Huron-Erie basin, since, these are in essential respects like those of the Michigan and Superior basins, although worked out in greater detail. Lake Chicago must, however, be brought into consideration, since in all save the earliest and the later stages, the waters from the Huron-Erie depression were discharged through the Grand River into this lake and thence by the so-called “Chicago outlet” into the Mississippi ([plate 20 A]).
The early Lake Maumee.—The area, outline, and outlet of this lake are indicated upon [Fig. 360]. Its ancient beaches have been traced, as well as the water-laid moraine beneath its former ice cliff; and no observant traveler who should take his way down the ancient outlet from Fort Wayne, Indiana, past the town of Huntington, could fail to be impressed by its size, suggesting as it does the great volume of water which must once have flowed along it. Now a channel a mile or more in width, its bed for the twenty-five miles between Fort Wayne and Huntington may be seen from the tracks of the Wabash Railway as a series of swamps merely, while at Huntington the Wabash river enters by a young V-shaped valley at the side, much as the Mississippi emerges into the old channel of the Warren River at Fort Snelling, Minnesota (see [p. 327]).
The Huron River of southern Michigan, which now discharges into Lake Erie, then found its lower course blocked by the glacier and was thus compelled to find a southerly directed channel now easily followed to the northern horn of the crescent of Lake Maumee.
The later Lake Maumee.—When the ice lobe had retired its front sufficiently, an outlet lower than that at Fort Wayne was uncovered past the city of Imlay, Michigan, into the Grand River, and thence through Lake Chicago and its outlet into the Mississippi. This old outlet south of Chicago follows the course of the present Drainage Canal and the line of the Chicago & Alton Railway. The traveler journeying southward by train from Chicago has thus the opportunity of observing first the beaches of the former lake, and then the several channels which were joined in the main outlet at the station of Sag ([plate 20 A]).
Fig. 361.—Outline map of the later Lake Maumee and of its “Imlay outlet” to Lake Chicago (after Leverett).
In this stage of our history Lake Maumee pushed a shrunk arm up past the site of Ypsilanti in Michigan ([Fig. 361]), the well-marked beach being found on Summit Street opposite the State Normal College. The Huron River, which in the first lake stage had followed the valley now occupied by the Raisin River southward into Indiana, now discharged directly into a bay upon this arm of Lake Maumee, and so formed a delta at Ann Arbor.