A FEW INTERESTING PHENOMENA ON THE ERUPTION 



OF USU 



Y. OINOUYE 



Imperial Tohoku University, Sapporo, Japan 



The eruptions of Japanese volcanoes for the past fifty years 

 have been almost invariably of the Strombolian type. But recently 

 there have been displayed five different types which may be listed 

 as follows: (i) an appearance of a new volcanic island, 1 (2) a new 

 lava dome in the crater of Tarumai, (3) 45 craterlets on the slope 

 of Mount Usu, (4) ejecting lava up in the craters of Asama 2 and 

 Mihara, 3 and (5) lava flows on Sakurajima. Partial descriptions 

 of the Tarumai and Usu have been published by the writer, 4 while 

 an account by Professor B. Koto of the third will appear in the 

 near future. 



In the southern part of Hokkaido, in North Japan, three vol- 

 canic eruptions took place between 1905 and 19 10. Komagatake 

 was in eruption in August, 1905, Tarumai in April, 1909, and Usu 

 in July, 1910. A line connecting these three volcanoes lies in a 

 northeast to southwest direction and represents the northern 

 extremity of the Nasu volcanic chain. The three volcanoes men- 

 tioned are about equally distant from each other (48 km.). The 

 explosion of Komagatake was simple and on a small scale, ejecting 

 fragments around the crater and ashes around the foot of the 

 volcano for a few days only, while that of the Tarumai 5 was more 



1 T. Wakimidzut, "Report on the Ephemeral Volcanic Island in the Iwojima 

 Group," Bulletin of the Imperial Earthquake Investigation Committee, No. 56 (1907). 



2 F. Omori, Bulletin of the Imperial Earthquake Investigation Committee, VI, No. 1 

 (1912). 



3 Y. Okamura, Bulletin of the Imperial Geological Survey of Japan, No. 48 (1914). 



4 Report of the Imperial Earthquake Investigation Committee, No. 64 (1909). Offi- 

 cial Report of Hokkaido Colonization (1910). 



5 Y. Oinouye: Report of the Imperial Earthquake Investigation Committee, No. 64 

 (191 1); H. Shimotomai, Zeitschrift der Gesellschaft fur Erdkunde zu Berlin, No. 9 

 (1912). 



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