RISE OF MOLTEN ROCK TO THE EARTH'S SURFACE 141 



Another agent which is effective in uncovering the buried struc- 

 tures of volcanoes is the action of waves on shores. Always a 

 relatively vigorous erosive agency, the softer structures of vol- 

 canic cones are removed with especial facility by this agent. On; 

 the shores of the island of Volcano, the little 

 cone of Vulcanello has been nearly half 

 carried away by the waves, so as to reveal 

 with especial perfection the structure of the 

 cinder beds as well as the internal rock 

 skeleton of the mass. Here the character- 

 istic dips of lava streams, intercalated as 

 they now are between tuff deposits and the 

 lava which consolidated in fissures, are both 

 revealed. 



In mid- Atlantic a quite perfect crater, the 

 St. Paul's Rocks, has been cut nearly in 

 half so as to produce a natural harbor FIG. 148. Map and gen- 

 (Fig. 148). 



In still other instances we may thank the 

 volcano itself for opening up the interior of 

 the mountain for our inspection. The eruption in 1888 of the 

 Japanese volcano of Bandai-san, by removing a considerable part 

 of the ancient cone, has afforded us a section completely through 

 the mountain. The summit and one side of the small Bandai was 

 carried completely away, and there was substituted a yawning 

 crater eccentric to the former mountain and having its highest 



wall no less than 1500 

 feet in height (Fig. 149). 

 In two hours from the 

 first warning of the ex- 

 plosion the catastrophe 

 was complete and the 

 eruption over. 



The eruption of Kra- 

 katoa in 1883, probably 



eral view of St. Paul's 

 Rocks, a volcanic cone 

 dissected by waves. 



IMtU 



FIG. 149. Dissection by explosion of Little 

 Bandai-san in 1888 (after Sekiya). 



the grandest observed volcanic explosion in historic times, left 

 a volcanic cone divided almost in half and open to inspection 

 (Fig. 150). Rakata, Danan, and Perbuatan had before con- 

 stituted a line of cones built up round individual craters sub- 



