PHYSICAL FEATUEES. 57 



and fills much of the interval between the lake and the Kankakee marsh. Its knolls rarely 

 reach 50 feet in height, but they are closely aggregated and so interspersed with basins that the 

 expression is in striking contrast to the bordering plains. The third area is in southern Ran- 

 dolph, southeastern Delaware, and northern Henry counties, in the reentrant between the East 

 White lobe and the Miami lobe. As already noted, this reentrant occurs in the highest part of 

 Indiana, where the altitude was influential in preventing the extension of the ice so far south as 

 on bordering lower tracts. The area, which is 6 to 10 miles wide and 30 miles long, is not only 

 filled with sharp knolls inclosing deep basins and sloughs but is also thickly strewn with bowlders. 



The morainic tracts mentioned were formed at the last or Wisconsin stage of glaciation. 

 The exposed surface of the older or Illinoian drift sheet presents only a few developments of 

 ridged drift. Some of these, however, are prominent, reaching a height of 50 to 150 feet, as, for 

 example, Chestnut Ridge ha Jackson County and Mount Auburn in Shelby County. 



The few eskers in Indiana -are but 10 to 25 feet in height and 3 miles or less in length. No 

 drumlins have been observed, and few kames are found outside of the strong morainic belts. 



MICHIGAN. 



Strong moraines are numerous in the southern peninsula of Michigan. They rival and 

 some of them far exceed the strongest in Indiana, reaching heights of 300 to 400 feet or more. 

 In the southeastern part of the State some of the moraines of the Wisconsin stage override 

 a basal ridge of pre- Wisconsin drift, and possibly they form only the upper part of the high 

 land northwest of the Saginaw basin. The bulk of the drift accumulation may have been 

 developed in pre- Wisconsin stages of glaciation. The plane-surfaced portions of the drift of 

 Michigan are chiefly on the borders of the peninsula and in a broad belt extending southwestward 

 from the Saginaw basin beyond Lansing; the latter, however, is interrupted by a few morainic 

 ridges with gently undulating surface. A considerable part of the plains was covered by glacial 

 lake waters. 



Eskers are numerous on the slope that rises toward the south from the Saginaw basin. 

 (See Pis. VIII-XI.) Their height is commonly only 20 to 30 feet, but their very steep sides 

 make them conspicuous. 



Drumlins are numerous in Antrim and Charlevoix counties (figs. 2 and 3), and a few are 

 found in Emmet, Cheboygan, and Alpena counties. They range in height from 60 to 70 feet 

 down to barely perceptible ridges. 



The lines of glacial drainage and the outlets of the large glacial lakes are conspicuous, some 

 of them being many times the size of the valleys excavated by the postglacial streams. This 

 is very apparent where a stream passes from a modern or postglacial valley into a line of glacial 

 drainage. The shores of the glacial lakes are on the whole inconspicuous, though characteristic 

 enough to have been recognized and traced by pioneer students. The Algonquin and Nipissing 

 shores are much more conspicuous than those of the earlier lakes, and probably those lakes 

 were longer lived. 



Sand dunes are conspicuous on the border of Lake Michigan in Lake, Porter, and Laporte 

 counties, Ind., the highest having an altitude of about 200 feet. The wind which formed 

 them derived its material partly from the abandoned shores and beds of the glacial Lake 

 Chicago and partly from the present shore of Lake Michigan. The largest are built up from the 

 present shore, those connected with the shore of Lake Chicago being usually less than 50 feet in 

 height. Low sand ridges 10 to 20 feet high in the Kankakee and Tippecanoe drainage basins 

 in northern Indiana and on the borders of the White, East White, Eel, and Wabash valleys in 

 central and southwestern Indiana, are apparently the product of wind action. 



In Michigan sand dunes are prominent along much of the shore of Lake Michigan. They 

 are highest at the river deltas, where many of them rise 200 feet above the lake. A few low 

 dunes occur on the border of Saginaw Bay. Dunes have been formed in places on the sandy 

 outwash plains among the moraines, and sand storms occur even now when high winds sweep 

 across cleared fields in these plains. 



