i9o6.) SEE— THE CAUSE OF EARTHQUAKES. 395 



the mountains were formed. On this view, earthquakes would be 

 of very small consequence geologically, because they are associated 

 only with destructive and not with constructive processes. But is 

 such a view tenable ? If earthquakes are not due to the same forces 

 which upheaved the mountains, what other forces besides these have 

 been active in the development of the globe? The only forces of 

 construction now felt upon the earth are those exerted in earth- 

 quakes. So far as we can see, no other constructive forces are at 

 work. Therefore, the forces felt in earthquakes are identical with 

 those which formed the mountains, and this is sometimes admitted, 

 though mountain formation itself is assigned to the wrong cause. 



Destructive forces such as erosion are wearing down the struc- 

 ture of the globe, while earthquakes are the only known forces which 

 are building it up. We take it, therefore, that so far from being of 

 little importance geologically the forces felt in earthquakes are of 

 the greatest importance, and most of the constructive forces in the 

 development of the earth are due to this cause. The destructive 

 effects of earthquakes are only incidental to the more fundamental 

 constructive purpose which underlies the operation of these forces. 

 When an earthquake occurs rocks in unstable positions fall, loose 

 sediment is shaken down, and other settlements occur, but the real 

 constructive work consists in upheavals, little by little it may be, 

 of mountains, islands, coasts, plateaus and larger areas. These 

 elevations are actually witnessed in certain earthquakes, and could 

 not possibly arise from any processes of collapse. Sometimes these 

 constructive forces work slowly and quietly, but usually with more 

 or less violence; and the usual method of elevation is by the injec- 

 tion of lava saturated with steam. 



What has been taken to be the cause of earthquakes, namely, 

 the slipping of rocks, is really the effects of more deep-seated ex- 

 plosive forces. Earthquakes^, therefore, are not due to the effects 

 of secular cooling, but to the vapor of steam arising from the pene- 

 tration of water into the heated layers just beneath the crust. If 

 earthquakes were due to cooling they ought to be as frequent in 

 desert regions as in deep seas along the shores of continents, where 

 they really are abundant. 



