MATERIALS COMPOSING THE LAND 



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groups in accordance with the manner in which they were 

 formed. These groups are igneous, sedimentary and meta- 

 morphic. 



The igneous rocks are those which have solidified from 

 a melted condition. They may have solidified deep down 

 within the crust, or on the surface, or somewhere between 

 the depths and the surface. If these rocks cooled slowly. 



CONGLOMERATE. 

 A sedimentary rock formed from old gravel beds. 



they will have a crystalline structure, as in granite, and if 

 very rapidly, a glassy structure, as in obsidian. Their 

 structure can vary anywhere between these two extremes. 

 A common dark colored variety of this kind of rock is 

 called basalt. There are many varieties of igneous rocks, 

 but they need not be considered here. 



The sedimentary rocks are those that are made by 

 deposition in water. When rocks are worn away into 

 fragments and these fragments are deposited in water 



