

'SH bulletin: museum of compakative zoology. 



23, 27) and islands lying in the neighborhood of the Koro Sea present 

 very steep angles. 1 This angle in places exceeds 30° or even 35°. 

 The slope is generally littered with huge spheroids of andesite. The 

 basalt forms a much more gentle slope, as may be seen by a traverse 

 of Taviuni. Usually the basalt is in very inconsiderable quantity and 

 appears to be of younger date than the andesite. 



The Recent Age of the Volcanic Phenomena. 



There appear to have been two distinct flows, one of andesite, the 

 other of basalt. Both appear to be very recent, even subsequent to the 

 last upheaval at Lau. Wherever volcanic rock is found in the smaller 

 islands of Fiji, whether that island be wholly volcanic or part volcanic 

 and part limestone, the eruptive rock is disposed of in gradually sloping 

 hills, with heaps of lava blocks scattered indiscriminately, or takes the 

 form of streams of volcanic stones littering the beaches. 



At Mango, Thithia (Plates 15 : 16, 19), Vanua Mbalavu, and Yathata, 

 cliffs of limestone exist forming inliers in flows of andesite lava. It 

 would seem that a great stream of andesite descended from higher levels, 

 parted near what is the inlier, and then swept over the cliff on either 

 side, and became confluent again at its base, where the lava was by de- 

 grees piled so high as to be nearly on a level with the top of the cliff, 

 and so produced a steep embankment sloping in one direction back 

 towards the base of the cliff inliei-, and in the other direction towards 

 the general trend of the lava flow. The contour of the lava bank as it 

 lies under the cliff suggests that of a viscous mass flowing round a large 

 obstacle and grown stiff before it had completely enveloped the 

 obstruction. 



In Mango huge sections of strata may be seen exposed in gullies that 

 have cut through the lower parts of the hill slopes (Plate 2, Figs. 

 2, 3). These strata have a decided dip, and consist of andesite tuffs 

 with large angular blocks of limestone scattered through the rock mass. 

 These blocks are as much as a ton in weight, and consist of coralline 

 rock indistinguishable from the present reef mass. A similar phenomenon 

 occurs in the 9-fathom lagoon to the south of Mango, where the tuff beds 

 are similar to those before described (vide map of Mango, Plate l). The 

 volcanic agglomerate is therefore clearly newer than the raised reef lime- 

 stone, and is in turn capped in places by a flow of andesite lava. 



The shape of the island of Vanua Mbalavu has been determined by a 



i See A. Agassiz, I. c, Plates 34, 46, 48, 50, 57, 58. 



