Volcauo Oshima, Idzu. 



77 



3d) by IV on the east' coast (PL YI. EF 5). The exposure afc 

 this locahty is as shown in Fig. 35, where L4 is the lava of 

 the present type, and Li that of the first type, i. e. the most 



Fig. 35. Ag Agglomerate bed. 



Jtj .Other éjecta bed. 



L\a Lib Lava of the first type. 



Li Lava of the fourth typa. 



widely spread basaltic bandaite. There tlie present rock-type occurs 

 in ten flows, each under Im. in thickness and with thin layers of 

 scoriœ and ashes between them. As may be seen from Fig. 35, 

 livas of the present type L4 must have been discharged from a 

 local vent during tlie extrusion of tlie lavas Lu and Luj, both of 

 which belong to the first type. 



Megascoinc Characters, — Megascopically, the rock is strongly 

 porphyritic with phenocrysts of plagioclase, olivine, and augite, 

 scattered through the groundmass without a trace of any regular 

 arrangement. Plagioclase phenocrysts, single or grouped, are most 

 abundant and average about 2 mm. in diameter, the largest being 

 over 5 mm. Olivine, though small in size (<1 mm.), is found abun- 

 dantly and is conspicuous for its characteristic luster. Tlie augite 

 phenocrysts, mostly in groups of two or three individuals, are about 

 2 or 3 mm. in diameter, and vary greatly in amount in different 

 flows. The groundmass is grayish and aphanitic and has pores of 

 various size (<3 mm. in diameter). 



Microscopic Characters. — Microscopically, the rock is sem- 

 patic. Single or grouped phenocrysts of calcic hytownile (Abj^An^g) 

 with the refractive indices «< 1.571 1. 572 <r^< 1.575 1.579 <r 



