THE VALPARAISO MORAINIC SYSTEM. 347 



system, as indicated below, is deeply trenched by the outlet from the gla- 

 cial Lake Chicago, which discharged from the southern end of the Lake 

 Michigan Basin through the Des Plaines Valley. 



In Lake County, Indiana, the contours are generally subdued, there 

 being few knolls more than 20 or 30 feet in height, Tributaries of the 

 Kankakee lead southward from the belt on the north border, greatly inter- 

 rupting the continuity of the main ridge. Similarly in Will County, 

 Illinois, the main ridge is trenched by the headwater tributaries of Hick- 

 ory Creek and of other streams flowing southward to the Des Plaines or 

 Kankakee. 



In Porter and Laporte counties, Indiana, the moraine is characterized 

 by sharper knolls than in Lake County and, as noted above, rises with 

 great prominence on its inner border. Lakelets are inclosed among the 

 knolls and occur also on the outer border of the morainic system in basins 

 occupying the edge of the overwash gravel apron. 



From the line of Indiana and Michigan northward the morainic system 

 usually presents sharp contours. The knolls range in height from 15 or 20 

 feet up to 60 or 80 feet. There are several places in which elevated tracts 

 several square miles in extent rise above the general level of neighboring 

 portions of the moraine. The most notable instances are as follows: In 

 Bainbridge Township, Berrien County; in central Lawrence Township, 

 Van Buren County; in southern Arlington Township, Van Buren County; 

 in northern Bloomingdale Township, Van Buren County; in northwestern 

 Trowbridge and northern Cheshire townships, Allegan Count}^, and in a 

 tract north of Allegan. There is usually an abrupt border on two or more 

 sides of these tracts, with a relief of 60 to 100 feet above neighboring por- 

 tions of the moraine. In the elevated tract north of Allegan the descent is 

 abrupt both on the north and east sides, and in Cheshire Township on the 

 north and west sides. The morainic tracts in northern Bloomingdale and 

 southern Cheshire have no very abrupt borders. The tract in Arlington 

 Township, with arm-like projections into Hartford Township, has an abrupt 

 border on all sides. The tract in Bainbridge Township has an abrupt border 

 on the north and west and also on portions of the east and south. Were 

 it not for the relief, these tracts would differ but little from the neighboring 

 lower portions of the morainic system, for they usually present only small 

 knolls and ridges on their surfaces. 



