SUVADIVA ATOLL. 409 



X. SuvADiVA Atoll (Plate XXI.). 



Suvadiva is such an immense atoll that it was scarcely possible to see sufficient of it, 

 even in five days, to venture on any conclusions as to its formation and origin. It is really 

 an isolated bank by itself, separated by broad channels from the other parts of the group, 

 in which Prof. Agassiz found 1130 fathoms towards Haddumati and 1292 and 1048 fathoms 

 towards Fua Mulaku and Addu'. A vast contrast in size to the latter and to the northern 

 banks of the line, Suvadiva, among the whole area of the Maldive and Laccadive groups, is 

 only comparable in a small degree to Haddumati, between which and Kolumadulu Prof Agassiz 

 found 1118 fiithoms. A better comparison would be with the Great Chagos Bank, which 

 might well represent an incipient stage of such an atoll as Suvadiva. 



On account of its great size, deep foundations, almost perfect rim, and large, open, and 

 relatively deep lagoon, it is necessary on almost any theory of the formation of atolls that 

 has been propounded, to assume for Suvadiva a greater age, a longer period of time since its 

 foundations were laid, than is necessary for any other bank of the Maldives and Laccadives. 

 With increased perfection of shape, too, the difficulty of deducing the stages by which the 

 whole was produced, increases very greatly. Recognising that there is much which can only 

 be understood by the analogy of other banks, I here merely draw attention to the changes 

 and conditions which seem of general applicability to the whole atoll, before passing to a 

 somewhat more detailed account of the parts I visited, than I have thought it necessary 

 to give in respect to the other parts of the Maldives. 



The land exhibits the usual changes found elsewhere, in some parts showing loss and in 

 others gain. The reefs everywhere to seaward have the ty|3ical outer slope, reef-fiat and 

 boulder zone. The latter is formed entirely of loose masses of rock, the skeletons of corals 

 and other reef organisms, fragments off the reef outside, and sometimes blocks of a consolidated 

 rock, that now lies above the low tide level. Some of the islands have to seaward a belt of 

 rock and there are also found isolated masses and pinnacles of the same on the seaward reefs. 

 Much of this rock shows its origin to be due to elevation, but no definite pinnacles are 

 found in the boulder zone, so that it is probable that the whole, or a considerable part, of 

 the breadth of the latter and all that of the reef flat have grown out since the elevation 

 took place. The raised rock is being eroded away, but loss at the present time is being 

 balanced by gain, though it is certain that the land once formed a much more continuous, 

 if considerably naiTower line, upon the encircling reefs. Along the lagoon sides of the islands 

 there is in places loss, but it is not general, the reefs being usually broad and in some 

 parts seeming to be growing out. The latter, however, is only the case in the more open 

 parts of the atoll, the opposite conditions prevailing to the S.W. Some of the reefs round 

 islands within the lagoon are growing out in places, but the islands themselves with very few 

 exceptions are gradually but surely being washed away. 



Points of the reefs, extending out into the lagoon by the mouths of passages, might 

 conceivably grow round in time to meet one another, and by fusing form velu in the rim. 

 I could, however, find no sign of their doing so, or having done so, while on the contrary- 

 such velu as there are in the rim, are gradually being put into connection with the atoll 

 lagoon. Some of the shallower passages are undoubtedly being closed up, both by the growths 

 of organisms on their bottoms and sides and also by the pushing out of points against the 



1 "An Expedition to the Maldives," Amer. Jour. Sci., ser. iv. vol. xiii. p. 301 (1902). 



