THE (ilJF.AT ERUPTION OF SAKURA-JIMA IN 1914. lOH 



According to Omoki, the stronger outbursts (second column) 

 were non -detonating and intratelluric, with comparatively large 

 earthquake motions, the double amplitude being 0.1 mm., and they 

 were followed by forcible ejections of ash clouds. The activity, 

 unsuccessful attempts at complete explosion, must have been taking 

 place deep in the channel. 



The weaker outbursts (third column) were of a surface nature, 

 accompanied by loud cannonading'^ and echoes of sound, and pro- 

 ducing air-concussions which shook windows at a distance. The 

 earthquake motions were, however, feeble, being ten times less 

 than the former. They were the result of the breaking open of 

 the cooled crust of lava vents by pent-up gases. As the detonat- 

 ing velocity was very great, the works of the blasting which were 

 achieved within a very short moment, were correspondingly of 

 considerable magnitude. It is a noteworthy fact that the number 



A 



of weaker outbursts, as Omoki says, is inversely proportional to 

 that of the stronger till the end of the fourth phase. 



The phenomena'^ of eruptions, macroscopically observed daily 

 by the writer on the field, were of two kinds, vu., a) the can- 

 nonading with shocks and quaking of ground occurred at the time 

 when a new or renewed fissure was opened, or a subterranean 

 gush of lava was caused by gaseous pressure conditioned by sudden 

 expansion at the orifices, and b) the thundering and roaring"^ with 



1) About the detonations see p. 6G, footnote. 



2) The writer carefully observed the night scene of the eastern vents at Fukiiyama. Single 

 booming was accompanied with shocks of the ground, emission of sparks and hurling of red-hot 

 stones. Continuous roarings and clinldngs, which immediately followed the preceding, signalized 

 the outwelhng of fluent lava and the subsequent down- rush of it from the margin of vents. 

 The two did not necessarily follow one another, but occurred quite indeiiendently. 



After his numerous observations in Stromboli, A. Sieberg found that strong exjilosions begin 

 with weak momentary tremthngs or oscillations of the ground, followed a few seconds later 

 by either a dull long thundering or a sharp booming. At the same time fumarole steam rises 

 accompanied with the trajection of lava fragments. — ' Einführung in die Erdbeben-und Vulkan- 

 kunde Süditaliens,' Jena, 1914, 8. 203. 



