CHAPTER II 

 THE MATERIALS OF THE EARTH AND THEIR ARRANGEMENT 



The mantle rock. The great body of the lithosphere is probably 

 composed of solid rock, but the solid rock is very generally covered 

 by a layer of loose material consisting of soil, clay, sand, gravel, 

 and broken rock, known collectively as mantle rock. The mantle 

 rock of many places consists of the disintegrated products of under- 

 lying rock formations. The upper part of such mantle rock is 

 constantly being blown away by wind and washed away by water, 

 but it is being constantly renewed by the decay of the rock below. 

 The mantle rock of some other areas, as the northern part of North 

 America and the northwestern part of Europe, consists chiefly of 

 an irregular sheet of commingled clay, sand, gravel, and bowlders, 

 known as drift. The drift was deposited by great glaciers, corn- 



Fig. 1. Soil and subsoil arising from the decay of limestone resting on the 

 uneven surface of the rock beneath. Southeastern Missouri. (Buckley.) 



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