58 N. Kaneiiaka 



as small dykes. In texture, the rock often approaches granite-porphyiy 

 on the one side and liparitc on the other. 



The porphyrite commonly intrudes into the Palaeozoic and Mesozoic 

 Formations. A tolerably large mass of porphyrite occurs in tlie 

 Triassic Formation of Nagato. The porphyi-ite found in the Misaka 

 Series is of a later eruption, probably of the Tertiary Period. 



The liparite flowed out in the Tertiary Period. Their tuffs, form 

 thick sediments in many places and are of wide distribution, especially 

 in North Japan. There are several varieties which are nevaditic, 

 trachytic or rhyolitic in texture. Yesan in Hokkaido is an active 

 volcano composed of this rock. 



The extensive eruption of andesite occurred in the Tertiary and 

 the Quaternary Periods. Of all volcanics, it has the widest distribu- 

 tion in the Japanese Islands and builds up nearly all active volcanoes. 

 It is accompanied in most cases by great deposits of tuifs, agglomerate- 

 tuffs and lava-breccias, and is sometimes laid as sheets between the 

 sedimentarics. Among various andesites, including mica-andesite, 

 liornl)lende-andesite and pyroxene-andesite, the last-mentioned is the 

 most frequent. Many sub-varieties of pyroxene-andesite, such as 

 augite-andesite, bronzite-andesite, two-pyroxene-andesite, oli vine-bearing 

 pyroxene-andesite, etc. are known to occur. 



The basalt occurring in Chugoku and northern Kyushu is genuine. 

 It is found in small areas as simple domes, and also as sheets and 

 dykes. Basalts found in Japan are in general andesitic in their 

 mineral constitution, and the olivine may or may not be present 

 among the ingredients ; but their silica contents are always less than 

 52^. They occur in large volcanoes together with pyroxene-andesite. 

 A unique basalt containing quartz phenocrysts is found in the vicinity 

 of Hagi in Nagato. 



4. Volcanoes and Hot Springs, 



Volcanoes : — Volcanoes are widely and regularly distributed in 

 accordance with the geological structure of the country from Chishima 

 to Taiwan. The majority of them are located in the Inner Zone and 

 are believed to have been formed in the age ranging from Tertiary 

 to Pleistocene. 



They are most numerous in the Chishima Islands, Hokkaido, 

 northern Honshu and Kyushu. Their number already known in all 



