THE GREAT ERUPTION OF SAKURA-JIMA IN 1914. 145 



overcome tlie burden of the higher part of tlic crater bottom, the 

 magma sought easy and sliort ways of escape to the surface, 

 where the mountain flanks i"emained yet uncovered with a lava 

 coat of mail. ïlio naked slopes on both sides, the only weak 

 portions of the whole mountain side, gave opportunity for the sites 

 of surfiice activity by means of two series of ventholes, one on 

 the front, the other on the rear. See Text-fig. 30. 



The ventholes were not in direct communication with the 

 local main reservoir, but only indirectly, where lavas were injected 

 sideways^ ^ through narrow and long passages from the main conduit 

 of the top- crater. It is the satellitic injection chamber, and there 

 were two of them which fed one or a number of vents overlying 

 them, and in turn were fed from the main channel. The vents 

 were mere openings of secondary injection chambers through a 

 thin skin of rock-crust which separated them. 



That the sateUitic chambers were supported with magma fi-om 

 the main channel is evident from the fact, that at the beginning of 

 the activity threads of steam clouds ascended from the top-crater 

 (Text-fig. 14 a [1]), which signahzed the immediate explosion on 

 the western flank [2] and ten minutes later on the eastern (Text- fig. 

 14 6 [3]). While the lava made its way through melting up the 

 crater conduit, partial gravitative differentiation took place, where- 

 by the lower column of lava changed in its chemical nature to a 

 heavy and basic one, and this lower column reënforced tlie 

 sateUitic chamber of Nabé-yama (Text-fig. 30). The fluent lava of 

 the east therefore consolidated to an olivine-bearing heavy and 

 basic rock, while that of the west solidified usually without the 

 above-mentioned mineral component. 



1) It is the subnormal eruption in the sense in which Perret understands such a motle of 

 subterrane lateral flow of lava. 



