THi: GREAT ERLTTION OF SAKUKA-JBIA IN 1914. 39 



^vill ill futures gradually decrease, "^rhrougli repeated eruptions, 

 which reuiarkably avoided the area (jf earlier flows, the former 

 graceful form hecame irregular, the structure complicate, and the 

 moimt grew and will grow sidewards. On the other hand, the 

 relief and plan are in course of time l)eing modified and simplified 

 l)y subaëriju a,nd ])luvial talus formations around the fringes of 

 the volcanic island, especially on the north and west coasts. 



The topography of the mountain s^ope or piano is therefore 

 entirely governed by pericentric radial flows. They are geologically 

 recent rocks not yet disintegrated, all l)eing black slaggy block- 

 lavas which can scarcely afford strong foothold to trees and 

 shrubs. Only the inter-lavaless strips and the talus formation as 

 well as the outwash plain near shore are available land for pasturage 

 and horticulture, for which the island is tolerably well known 

 (Text-fig. 7, Zones IV. and Y.). Arable land is reduced to a 

 minimum, owing to the poverty of soil and the scarcity of water. 



C) Hydrography.— From the geologic structure and the 

 topographic form as outlined above, we can w^ell understand, that 

 only the radial gullies on the slope serve as draining channels 

 for meteoric water. On the west and north talus and torrential 

 streams spread and deposit gravelly alluvial fans. As the ground 

 is full of clefts, or of loose nature, the w^ater is readily soaked in 

 within a short distance. Consequently, there exist no permanent 

 spkiîjgs streams on the island. Copious sprln(/s,^^ however, issue 

 at some places on shore from the under gravel bed, or one can 

 get plenty of ground water in shallow wells dug at the lower 

 end of wash plains. 



1) See ' Changes in the efflux of hot-springs,' p. 17, and ' Hot -springs," pp. 56, 57, itud 

 lastly, 'Hot and cold s])rings,' ]>. 62. 



