THE CAUSES OF EARTHQUAKES 



written about the shifting of materials from the land to 

 the sea by the processes of denudation and erosion set 

 up by rain and wind and carried out by streams and 

 rivers, will easily discover where and how the shifting of 

 great weights of the earth's surface goes on. Little 

 by little great weights are taken from one place on the 

 earth's surface to another, as we might shift the weights 

 in balanced scale-pans grain by grain, till at last the 

 heavier scale-pan goes down quickly, or it may be with 

 a crash, and the " fault " occurs, while the earthquake 

 follows. 



There remains another question, however, to be an- 

 swered, and it is, How were the mountains formed? 

 Mountains are very closely connected with earthquakes, 

 for nearly all the regions of the earth where the great 

 disturbances take place are in the neighbourhood of great 

 mountain ranges ; and many, indeed most, of the students 

 of earthquakes believe this to be the case, because the 

 great weight of the mountains, especially when near the 

 deep sea, induces pressure on the rocks, and consequently 

 slipping and "faults." But the causes of mountain forma- 

 tion are very difficult to show with certainty. One such 

 explanation, that of the continual shifting of portions by 

 weight of the earth, we have already given. There is 

 another one which may perhaps supply an additional 

 cause. It is that just as " faults " produce earthquakes, 

 perhaps in some cases earthquakes produce " faults." In 

 the illustration we gave of the bottle-neck being broken 

 by continual pressure, or the slide of a microscope 

 suddenly breaking with a crash, because the increasing 



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