PRELIMINARY NOTES ON SOME IGNEOUS ROCKS OF 



JAPAN. IV 1 



S. KOZU 

 Imperial Geological Survey of Japan 



IV. ON LAVA AND ANORTHITE-CRYSTALS ERUPTED FROM THE 

 TARUMAI VOLCANO IN 1909 



Introduction. — The volcano Tarumai is located at a distance of 

 about 42 kilometers south of Sapporo, the chief city of Hokkaido. 

 Though the volcano has long been known as one of the active 

 volcanoes in the district, it has become the object of special atten- 

 tion since the outpouring of lava, which took place in April, 1909, 

 forming a dome of 134 meters in height as measured from the 

 neighboring ground, and adding 40 meters to the pre-existing 

 highest peak of the mountain, which is 1,015 meters above the sea- 

 level, according to Oinoue's report. 



A revival of the exhausted volcanic energy, which had remained 

 in the solfataric state since the comparatively great explosion of 

 August 17, 1895, took place at the beginning of the year 1909. 

 After that several outbursts and shocks were reported from the 

 region. At last, in the course of about 24 hours, from the evening 

 of the 17th to that of the 18th of April, lava of about 20,000,000 

 cubic meters in volume, measured by B. Koto, was poured out of 

 the explosive crater, and a dome was formed which is shown in the 

 accompanying photographs (Figs. 1 and 2). 



Reports of the event, written in Japanese by D. Sato and Y. 

 Oinoue, have been published by the Imperial Geological Survey of 

 Japan and the Earthquake Investigation Committee, respectively. 

 The following brief petrographic description was made by the 

 writer on the specimens collected by D. Sato. 



Megascopical characters. — The specimens at hand have in general 

 a glassy and ragged appearance. Those taken from the ejecta are 



1 Published by permission of the Director of the Imperial Geological Survey of 

 Japan. 



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