234 PLEISTOCENE OF INDIANA AND MICHIGAN. 



from Clare County, where the West Branch morainic system is separated into several members, 

 the relief of each ridge is less than 100 feet except in northwestern Isabella and eastern Mecosta 

 counties, where it is 200 feet or more. 



Along the outer face of the West Branch morainic system throughout its entire length from 

 the Au Sable Valley to the Grand River outlet, the relief is moderate, being generaUy less than 

 100 feet. In northern Clare, southeastern Roscommon, and western Ogemaw County, how- 

 ever, it in places reaches 200 feet. 



The relief of the Gladwin Ridge is not more than 50 feet on either border except in Isabella 

 and southeastern Clare counties, where it reaches nearly 100 feet on the inner border. 



CHARACTER. 



The closely crowded parallel ridges of the more massive portion of the West Branch 

 morainic system become more and more distinctly separated in passing southward to the 

 Grand. River outlet. They are broken by a few gaps through which streams have passed from 

 the outer border district into the inner border plain, the most conspicuous being that utilized 

 by Chippewa River, which heads in the plains in southwestern Clare County and makes its way 

 through each and all the members of the system to the inner border plain at Mount Pleasant. 

 Pine River also cuts through several of the morainic ridges at places where they were weakly 

 developed. 



The great majority of the knolls through the entire length of the morainic system are 

 relatively inconspicuous, but in a few places they rise to 100 feet or more, the most conspicuous 

 bein<* in the highest part in Roscommon and neighboring parts of Clare and Ogemaw counties. 

 Ranges of hills in eastern Mecosta County also rise above 100 feet, but from the latitude of 

 Mount Pleasant southward the moraines generaUy are composed of low knolls. A few knobs 

 in the vicinity of Stanton are 100 feet more or less in height, but these seem to be outside the 

 system under discussion and were apparently formed during the retreat of the ice from the 

 Charlotte morainic system. 



Basins are conspicuous along the entire massive morainic belt and along its constituent 

 members toward the south. Many of them contain shallow tamarack swamps, but not a few 

 hold small lakes. 



The Gladwin Ridge has a swell and sag topography with fewer basins than characterize the 



main system. Its most hilly part is in Ogemaw County, where it also carries basins and some 



lakes. 



STRUCTURE OF THE DRIFT. 



The outer portion of the massive morainic tract from Au Sable River southwestward to 

 Mecosta County, west of Mount Pleasant, contains a large percentage of gravel and sand, but 

 much of its inner border carries a clayey till. In consequence much of the inner slope has been 

 converted into farming land, and the outer is in large part a desolate waste in which brush is 

 growing up to take the place of the pine forests that have been removed. In places the pro- 

 ductive agricultural lands extend nearly to the outer border of the morainic system, for instance 

 northeast and west of Harrison and in the northwest corner of Isabella County. The greater 

 part of the outer slope of the morainic system, however, seems better suited for forest than for 

 agriculture. 



The greater portion of the morainic system from Clare County southward to the Grand 

 River outlet has a soil suitable for productive farming and is largely under cultivation; the 

 moraines are better farming land than the depressions that separate them, the latter being 

 sandy and swampy lines of glacial drainage. In Gratiot, Montcalm, and central Isabella 

 counties the moraines are separated by broader strips of fertile till plain, which he on the inner 

 slopes of the moraines and not, like the drainage channels, on the outer slopes. The constant 

 repetition of the series, drainage channel, moraine, and till plain, brings out- clearly the glacial 

 and fluvioglacial relations and conditions. 



