40 FOYE. 



western side of Taviuni, looking southward along the coast towards 

 the outlying island of Ngamia. It illustrates the low topography of 

 recent basalt flows which cover the older hills in northeastern Taviuni. 

 It also shows the mature topography of Ngamia and its embayed 

 shore-line. The irregular outline of this island is in distinct contrast 

 to the rather regular outline of Taviuni. If the latter island, like 

 Ngamia, has been submerged, it should also be embayed along its 

 northern shore. The lack of such embayment indicates that either 

 still-stand or uplift has characterized the recent history of the island. 

 The continuous series of vents along the northeast-southwest cen- 

 tral ridge of Taviuni is doubtless located on a fracture-line. Block- 

 faulting along parallel lines possibly accounts for the depths of 75 to 

 150 fathoms along the eastern and western sides of the island, close to 

 the shore. Yet no evidence favoring this hypothesis is at hand, and 

 the present slope of the modern basalt flows, if continued beneath the 

 sea, would furnish almost as steep a descent to deep water. 



.^ji^stgiS'JjisM?^ 



Figure 19. View of Ngamia and Northwestern Taviuni from Nangasau. 



Besides an intermediate period of uplift, Taviuni, like the district 

 about Mbutha Bay, shows two other distinct periods in its develop- 

 ment. The older is that of mature or late-mature erosion and lateriti- 

 zation of andcsitic rocks; the younger, that in which more basic rocks 

 were extruded. 



The points of greatest importance to be noted in the following table 

 are: — 



1) Old cores of plutonic rocks form the centers of both Vanua Levu 

 and Viti Levu. 



2) Most of the districts show one period of great subsidence. 



3) The submarine volcanic rocks of central Vanua Levu are lack- 

 ing in eastern Vanua Levu and Taviuni. 



4) One period of rhyolitic activity, two periods of andcsitic activity, 

 and a later period of basaltic activity are manifested in these islands. 



