SUBMARINE VOLCANOES, 



309 



all considerable. If the depth be slight, or the 

 activity of the volcano very great, the water bubbles ; 

 a column of smoke rises above the level of the 

 sea ; flames, scoria3, or incandescent stcmes demon- 

 strate the presence of a volcano. The sea changes 

 colour to a greater or less extent, and becomes warm. 

 Ships receive a shock as if they had struck a rock ; 

 indeed, in some cases the concussion is so violent 

 that vessels have lost their masts. 



Volcanic products of every kind, however, ac- 

 cumulate at the bottom of the sea, covering every 



r-. C 



Fig. 60. — Eruption of a Submarine Volcano. 



living thing ; streams of lava, masses of scoriae, and 

 rocks, contribute to an elevation of the soil which 

 must eventually raise it to the light of day. Such 

 is often the origin of volcanic islands. 



Submarine earthquakes disturb the sea through- 

 out its whole depth, causing the terrible waves of 



