THE 



AMERICAN JOURNAL OF SCIENCE ''' 



[FOURTH SERIES.] 



Art. IX. — Physiographic Development of the Tarumai Dome 

 in Japan ; by Hidezo Simotomai (Tanakadats), Tohoku 

 University, Japan. , 



The rise of a new dome on the top of Tarumai volcano in 

 Japan attracted much attention among the naturalists of the 

 world. Though it was not an unusual type of lava eruption, 

 itsphysiographic development is observed better than others 

 of the same kind. As the structure of the volcano and the 

 history of its recent eruption in the year 1909 have been 

 described by many authors, they will be touched upon only 

 briefly here. 



Tarumai is a flat volcanic cone formed principally of andesitic 

 scorias and ejectas and its site is in the volcanic region 

 of Hokkaido in lat. 42° 41^ 30^' IN", and long. 141° 21' 40'^ E. 

 Towards the south it slopes gradually to the Faciflc coast, while 

 to the north a short ridge connects it with an extinct volcano 

 called Hu-uppusi-nuppuri. Both cones rise from the deep water 

 of Sikots Lake, of which the area is 78 sq. km., with surface 

 298"" above sea-level and bottom about 60"' below sea-level. 



The volcano has a double crater on its summit and the 

 Som7na-w2^\ is much dissected on the southwest and southeast. 

 The eastern side culminates in Higasiyama at the height of 

 1016"" above sea-level and before the eruption this was the 

 highest point of the volcano. 



According to Prof. Oinoue, the inner crater, which is now 

 full of the recent lava, was formerly oval in shape, with major 

 axis of 670"' running ]N'.10°W. and minor axis of 550™; its 

 depth was about 80™. The circular bottom of the crater had 

 a diameter of 60™, and from some pits in it sulphurous gas 

 continuously issued. 



Am. Jour. Sci.— Fourth Series, Vol. XLIV, No. 260.— August, 1917. 



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