THE MAKING OF MOUNTAINS 33 



less elevated tracts which have been gradually reduced 

 in extent, and largely subdued by the forces of decay. 

 Mountains of the second class are the remains of 

 plateaus or raised blocks of the earth's crust which 

 have been eaten away unequally by frost and rain and 

 other "weathering" agencies. But mountains of the 

 first class are elevations produced by uplifts and 

 crumplings of the earth's crust or by volcanic erup- 

 tions. This will become clearer after we have con- 

 sidered the different kinds in more detail. 



From a hole broken in the earth's crust there may 

 be an eruption of molten rock or lava, and the accumu- 

 lation of this, along with slags, cinders, rock frag- 

 ments, and dust may form Accumulation mountains of 

 the volcanic type. A simple volcano- may form a 

 conical mountain with a central pit or crater above the 

 mouth, and this may eventually become a crater lake. 

 When the looser materials are swept away the throat 

 of the old volcano, choked with solidified hard rock, 

 may be left as a central core or boss. Sometimes, to 

 take a very different case, the vents of the volcano may 

 have belched out floods of lava, burying a wide range 

 of country and forming lava plains and lava plateaus. 

 There are many different kinds of volcanic mountains, 

 but they do not concern us at present. All we need 

 just now is a clear picture of one of the ways in which 

 mountains are formed, and it should be noted that this 

 kind of mountain-making is still being illustrated 

 around more or less active volcanoes like Vesuvius 

 and the lofty Mauna Loa in Hawaii. 



As examples of volcanic mountains we may name : 

 Fuji-Yama, in Japan, Cotopaxi in Ecuador, Popocate- 

 petl in Mexico, the Peak of Teneriffe, the cone of 



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