J32 ^'ol. XLni., Art. fi. — S. Tsnboi : 



Kôzushima also shows very young morphographic features. 

 There is no good reason for doubtmg that the record on the 

 vulcanism in 838 (see the foot-note on p. 129) refers to the 

 eruption in Kôzushima. 



From the above the rhyohtic insular volcanoes in Idzu appear 

 to be quite young, and it is very probable that their eruptions 

 took place even in historic times. 



It -will not be out of place here, to call attention to the geology 

 of the Idzu peninsula which is closely related to that of the Idzu 

 islands, for it is necessary in discussing the geology of isolated 

 districts to correlate them with the geologically connected main land. 



The geology of the Idzu peninsula was studied by Ishiwaea^\ 

 and the southern part in particular by Kôzu'\ The present- 

 wi'iter also had an opportunity of making a hasty journey through 

 the peninsula in January of 1918, and to secure some acquaintance 

 with the rocks there exposed. The time available, however, was 

 too limited for more than an observation confined only to - a few 

 parts along the eastern shore and the small area near Sliimoda"\ 



So far as is known to the writer principally from books and 

 onl}^ to a limited extent from brief personal observation, the geology 

 of the Idzu peninsula is as follows : — 



The peninsula is built up largely of volcanic rocks. According 

 to KÔZU, the rocks constituting the southern i^i t of the peninsula 

 are, in the order of their eruption : i)lagioliparite, potash-liparite, 

 propylite, liparite, dacite, and pyroxene-andesite ; all but potash- 

 liparite accompanying the tuffs and breccias besides the solid 

 lavas. In his opinion the extension of these rocks began in the 



1 '• Volcanoes in the Idzu Peninsula," Eeport Earthq, Tûvent. Com.. No. 17, 1898 (in Japanese). 



2) " The Geology of the Southern Part of the Idzu Peninsula," Eeport Imp. Geol. Sv.ri:, 

 No. 38, 1913 (in Japanese). 



3) TW 



