April, 1902.] .4 Possible Cause of Osars. 257 



A POSSIBLE CAUSE OF OSARS. 



Geo. H. C01.TON. 



On the 20th of April, 1901, there fell in north-eastern Ohio an 

 unusually heavy snow covering the ground to a depth of from 

 twenty inches on a level to seven feet in drifts. The snow came 

 very rapidly and went very rapidl3\ During the period of rapid 

 melting strong currents of w^ater ilowed beneath the .snow which 

 in some cases carried along much sediment. It was my good 

 fortune to observe a point near the borders of a gently sloping 

 plowed field where one of these streams, becoming clogged, rose 

 to the surface and flowed for a short distance over the dense 

 snow, spreading the abundant sediment, which it carried in a 

 sinuous belt along its channel. After a time the stream deserted 

 this surface channel and found a new one beneath the .snow. As 

 the snow melted the belt of sediment which had accumulated in 

 the channel on its surface gradually settled, and when the snow 

 had disappeared it rested upon the turf that bordered the plowed 

 field as a minature osar. 



While it is rightly assumed that the surface of the glacial ice- 

 sheet was for the most part clean and free from earth}- deposits, 

 5^et near its southern margin there may have been much sediment 

 on its surface. Streams of great force and volume, heavily laden 

 with glacial detritus, flowed beneath the ice, and it is possible, 

 and even probable, that the shifting of the melting ice, under- 

 mined by the flowing waters, and the displacement of the loose 

 material of the deep moraine as the ice reacted upon it, would 

 occasionally clog the channels of these streams and compel them to 

 find new ones. In most cases the new courses would be beneath 

 the ice as before, but it is reasonable to assume that sometimes 

 the obstructed stream, like the rill in the snow-field described 

 above, would rise through some crevasse and flow for a time over 

 the surface of the ice. Such a stream w^ould have its rapids 

 swept clean of sediment, and its stretches of deep and sluggish 

 water in which would accumulate belts of sand and gravel. 

 When the stream deserted its ice channel, as it surely would in 

 time, these sinuous belts of sediment would lie almost undisturbed 

 upon the surface of the glacier, and they would be left finally, 

 when the ice had disappeared, as ridges over the surface of the 

 land, forming what glacialists call osars, or serpent kames. 

 Indeed, such surface accumulations would be far less likely to be 

 disturbed and obliterated by subsequent changes than would 

 those gravel belts which, in spite of the many difficulties involved, 

 it has been assumed, might be formed beneath the ice by sub- 

 glacial streams. 



Hiram College, Hiram, O. 



