366 SEE— THE CAUSE OF EARTHQUAKES. [October 19, 



Let the accompanying figure illustrate a section perpendicular 

 to the shore of the sea and land, on a coast like that of Chili or Peru, 

 where this phenomenon has so often been observed in a typical way, 

 and the water is deep. 



Suppose a volcano to be formed at some distance, say 50 or 100 

 kilometers from the shore. If a great wave is produced we may 

 assume the volcano to be raised to a height of 1,000 or 2,000 meters, 

 or even higher ; but as the sea is seven or eight kilometers deep, this 

 will only reach one-seventh or, at most, one-fourth of the way to the 

 surface. In the throes 01 the earthquake the volcano is raised, and 

 the water forced up immediately over the eruptive center; and the 

 steam, stones, lava, dust and ashes are driven upward towards the 

 surface, as in the explosion of a land volcano. The explosion is 



Fig. 14. 



Submarine volcano. 



resisted by the great depth of the water, which is hurled upward in 

 a violent current from the orifice. The steam condenses to water 

 by the low temperature of the ocean, and the other gases are ab- 

 sorbed, whether coming from the bed of the sea or formed in the 

 water by the intense heat of the red hot lava. The current of steam 

 and flying stones, lava, sand and ashes, by beating against the over- 

 lying stratum of water, forces such rapid upward movement that the 

 level above is forced bodily upward, it may be several hundred 

 meters. But the fluid medium is continuous and presses in on all 

 sides, and is therefore drawn upward on all sides about the base of 

 the cone to supply the uprush of water. The currents thus forced 

 with enormous violence are shown in the figure. The drawing 

 upward of the water about the base of the cone causes the inflow 

 of water from the bed of the sea towards the base to maintain the 

 upward movement, following the upheaval and explosion of the 

 volcano. Thus the water near the shore some distance away is 

 sucked down in the general lowering of the level and the sea is 

 observed to slowly recede at the shore. All this is done in a short 



