NOTES ON THE SAND DUNES OF NORTH- 

 WESTERN INDIANA 



GEORGE B. CRESSEY 



Yale University, New Haven, Connecticut 



Of the sand dunes of North America, few present more interest- 

 ing phenomena than those bordering the southern shore of Lake 

 Michigan. Not only do they illustrate all phases of dune activity 

 but they have a significance in ecology and post-glacial history as 

 well as rare scenic beauty. They are conspicuously developed in 

 northwestern Indiana, their maximum development being confined 

 to the 20 miles of shore between Gary and Michigan City. Heights 

 of 100 feet are common and the height of the frontal ridge along 

 the lake commonly ranges from 75 to 175 feet. Parts of the dune 

 complex are fixed and forested, while in other areas the sand is 

 being shifted. The dunes are limited largely to a belt about a 

 mile wide along the shore, although in places low dunes extend 

 several miles inland. 



Along the western shore of Lake Michigan for 20 miles north of 

 Chicago the waves are actively cutting into the thick drift, here 

 composed of rather fine materials. This wave-cut cliff may be 

 seen on the Highwood topographic map and in places is more than 

 80 feet high. A very considerable amount of erosion has taken 

 place and some of the debris has been transported southward by 

 the alongshore currents. Evidence of this movement is seen in 

 the accumulations of sand on the northern sides of piers and the 

 southerly deflection of streams' entering the lake where unprotected 

 by breakwaters. With the wear and sorting involved in the trans- 

 portation, the material which reaches the southern end of the lake is 

 almost exclusively quartz sand. Here the topography and prevail- 

 ing winds are such that deposition takes place. The shore sands 

 become the prey of the winds and the dunes reach their greatest 

 development. 



In order to examine the effect of the wind transportation on the 

 sand grains, nearly fifty samples were gathered along seven lines 



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