106 



ART. 3. — B. KOTO 



The Southern main arm (Text-figs, 19 [p. 74] and 24) of the 

 iiuent lava pushed southwards under the sea with a thickness of 



100 m. where the 



bottom is now only 

 30 fathoms, while 

 it w^as formerly 06 

 fathoms deep, giv- 

 ing a maximal 

 difference of 60 

 fathoms which is 

 equivalent to a 

 vertical extent of 

 over 100 ?7Z. of the 

 submarine lava- 

 sheet. The eastern 

 submarine arm 

 was deflected east- 



Fig. 24.— Distribution of the Nabé-yamn lava-flows, land, marine WardS by the head- 

 and submarine. The heavy line, marked ' Sept. 1915,' shows j.^^^^ ^j Sakkabira 

 the subiierial extent of the lava-field by the recent survey 



(p. 104, footnote). witli Icss intensity 



of forward movement and corresponding decrease of thickness to 

 about half that of the southern. 



As will be seen on tlie Sketch Map (Text-tig. 24), the southern 

 arm of the submarine flow moved farther forwards pushing up 

 the muddy bottom to an extent of 28 7/?. This outer muddy shoal 

 is now 60 fathoms deep, while it was formerly 70-80 fathoms. As 

 the soundings brought up nothing but samples of mud, the bottom 

 of the shoal is evidently not sheeted with lava, and the writer 

 deems it better to exempt it from the submarine lava area, 

 althougli in the following calculations it is assumed as a lava mass. 



