GLACIAL OR ICE-LAID DEPOSITS 



43 



faces over which they moved (Fig. 35), producing immense quan- 

 tities of rock flour. The whole glacier was an immense mill that 

 was slowly grinding rocks into powder. This rock flour was lib- 



Fio. 35. Glacial grooves or stria? on rork surface. Northern Ohio. (From Elements of 

 Geology, Copy: i^ht 1911, by Kl.ot Black welder A llarlanH. Harrows. American Book Co.) 





Fid. 30. Typical topography of terminal moraine near Ocomowoo, Wisconsin. Wisconsin 

 Geol. Survey. (Fount-man.) 



erated by the melting ice and was distributed over the land by water 

 and wind, forming the very best of soil material. In some in- 

 stances it was carried much farther than tlu> limit of the ice sheet 

 and distributed as immense aprons beyond the ice front. 



