THE (iEEAT ERUPTION OF SAKURA-.TIMA IN 1914. 185 



an altitude of 300 m. burst out 10 minutes later than the western 

 ones, located also at 300 m. {See Text-fig. 14 b, right west, left east). 

 The outpouring of fluent lava, which began eight hours after the 

 first outburst, must have been correspondingly later in the eastern 

 vents, and the latter lavas should be assumed to be of younger 

 birth. Consequently, it is not unreasonable to suppose that the 

 eastern flows came from a lower horizon {see Text-fig. 30) of reservoir 

 where, prior to the eruption after long quiescence, magmatic differ- 

 entiation might have taken place either by selective crystallization 

 or by gravitative concentration, or else in some other w^ay. 



The eastern lavas on tliis account are heavy, more Ijasic and 

 thin-fluid, flowing down farther seawards in submarine flows as 

 compared with the western ones. {See Text-figs. 19 and 24.) Again 

 the eastern lavas are less slaggy (comparatively compact), deeper 

 in color and higher in specific gravity, the lustre being, however, 

 variable in rocks on both sides ranging from pitch-black to vit- 

 reous and dull-gray. 



A peculiar feature, which attracted the writer's attention, is 

 the abundancy of lapilli on the eastern side.^^ The sea was at 

 that time thickly covered with floating pumice fragments only on 

 the eastern water but not the western channel. The basic eastern 

 lava, saturated with volatile constituents, seems to have been well 

 adapted to the formation of spongy éjecta. It is superflous to say 

 that the west winds during the eruption blew suspending and 

 projecting éjecta toward the east, thereby contributing a mass of 

 subaërial fi-agmentary volcanics to the eastern side in no small 

 measure. 



Phenocrysts. — Olivine,'^ which is always anhedral, is universally 



1) See aate, pp. 68 (footnote), 82. 

 '2) See tviüe, page 177. 



