26 Vol. XLIII.. Art. 6. — S. Tsnboi : 



at intervals. Moreover, as is indicated by their occurrence in 

 alternate layers with the somma lavas, tlie ejection of tliese scorise 

 and the extrusion of tlie somma lavas must liave succeeded one 

 another. 



Summarizing all that has been stated in the present chapter, 

 the volcanic actions liave taken place in various parts of tlie 

 island. They are represented by the extrusion of effluent flows, 

 the ejection of scoriaceous materials, the building oi parasitic knobs, 

 the injection of dykes, etc. Above all, the southeastern part of 

 the island was especially subject to volcanic actions : scoriae were 

 repeatedly ejected in thick accumulation; magmatic intrusion came 

 so near the surface as to cause phroatic explosions ; and numerous- 

 dykes were intruded, as we see on the sea clift' opposite to 

 Fudeshima.'^ 



The Caldera. 



The somma is truncated at the top with a ring- wall surround- 

 ing a huge oval caldera, the major and minor axes of which are 

 3.2 km. from N.N.W. to S.S.E. and 2.5 hm. from E.N.E. to W.S.W. 

 respectively. 



The crest line aroimd the ring- wall is not uniform in its 

 altitude. Its highest point is Shiroishi'^ (2d) on the southeast, at- 

 taining a height of 737 m. above sea level. The second highest, 

 Kagamihata'^ (Ic), lies on the northwest (604 m.). The rim of 

 the encircling cliff is, as a rule, higher on the east (620-720 m.) 

 than on the west (560-600 m.) (Fig. 15). 



There are two possible explanations for the genesis of the 

 caldera : (1) the blowing away of the apical part of the mountain 

 by explosive action, (2) the depression of the sunnnit. 



1) m% 2) öS 3) it's 



