CHAPTER XXVII 



SOME CONCLUSIONS AND THEIR BEARINGS 



Vanua Levu is a composite island built up during a long period 

 of emergence, that began probably in the later Tertiary period, by 

 the union of a number of large and small islands of volcanic 

 formation representing the products of submarine eruptions. It 

 differs in this respect from Viti Levu which is much more massive 

 in its profile and possesses a greater proportion of plutonic rocks. 

 When, however, Viti Levu comes to be systematically examined, 

 it is likely that traces of its composite origin will be found. The 

 evidence seems to show that it is older than Vanua Levu ; but they 

 are both situated on the same submarine platform, the area of which 

 is nearly equal to the combined areas of the two large islands that 

 rise from it. 



This platform, as indicated in the small plan of the group, is 

 limited by the lOO- fathom line in the charts ; but since the reefs 

 on their seaward slopes plunge down precipitously, such a line 

 practically serves to delineate the margin of the plateau. It has 

 been my object to show on previous pages ^ that this submarine 

 platform is a basaltic plateau built up by submarine lava-flows and 

 incrusted with coral reefs and their deposits. It has been pointed 

 out that this platform passes gradually, as it proceeds landward, 

 into the low-lying basaltic plains that constitute the sea-border in 

 the western part of the island, where the breadth of the submerged 

 plateau is greatest. The basaltic flows of the plains often display 

 the almost vertical columns of slightly inclined flows. Their 

 apparent termination at the sea-border, where they are in places 

 covered over with submarine deposits, cannot, however, be accepted 

 as their real limits. According to my view they extend several 



1 See pp. 2, 15, 18, 56, 62, 72, &c. il 



