154 



ICE DEPOSITS 



balance each other, all the burden which it is transporting is 

 deposited in a great mound or ridge, the terminal moraine. 

 Moving ice does not sort the material which it carries, as flowing 

 water does, because in a glacier there is no such definite relation 

 between velocity and transporting power. Hence, the terminal 

 moraine is unstratified and is composed of materials of all sizes, 

 from dust and sand up to great boulders weighing hundreds of 

 tons, all mingled together in confusion. In the case of a glacier 



FIG. 58. — Perched block of sandstone resting on trap, Palisade Ridge, N.J. 

 (Photograph by Salisbury.) 



which carries the principal part of its burden upon its upper sur- 

 face, the terminal moraine is chiefly made up of angular blocks 

 that have undergone little or no abrasion, together with earth, 

 sand, gravel, and whatever kind of material the overhanging cliffs 

 may have delivered to the moving ice. Mingled with these 

 materials, however, will be found more or fewer of the character- 

 istically worn and grooved glacial pebbles and boulders, which 

 have been dragged along under the ice, and scored and polished 

 by the rocky bed. There will also be found some, at least, of 

 the sand and fine rock flour which the glacier's own movement 



