CHAPTER XVI 



VOLCANOES AND MOUNTAIN 

 FORMATION 



THE great prominence which we have given in the 

 preceding pages to earthquakes is owing to the 

 growing belief in the influence of earthquakes on 

 the appearance and structure of those portions of the 

 world's crust which are known to us. There are two 

 views which we can take of earthquakes. One is to 

 regard the larger number of them as being caused by 

 slipping movements of the earth's crust. Looking at 

 things in this way we should say that whenever there 

 was a sudden break in the earth's strata, such as might 

 occur (in accordance with an illustration given in a pre- 

 vious chapter) if all the level strata were broken up 

 like a crumpled page of type then that an earthquake 

 would result. So that whenever we saw what geologists 

 call a "fault" in strata we should know that an earth- 

 quake had occurred there. And why did it occur? 

 Well, if we had a massive column of steel or of granite 

 five miles high, the steel or granite at the bottom of 

 the column would have to sustain such an enormous 

 weight of material above it that it would begin to 



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