UNEQUAL DEPTHS OF LAGOONS AND BANKS 549 



but that, on the contrary, coasts of recent submergence, and especially 

 coasts of long-continued submergence, oifer highly favorable conditions. 

 Hence either a slow rise of the ocean or the slow sinking of a coast will 

 favor the growth of reefs, all the more if the change of level be long 

 continued at not too rapid a rate. But as reef-bordered coasts have suf- 

 fered submergences of various amounts and dates, frequently associated 

 with neighboring emergences, they can not be accounted for by a uni- 

 versal, uniform, synchronous rise of the ocean, and must therefore be 

 accounted for by local, variable, and non-synchronous subsidences of the 

 coasts concerned; and this conclusion supports Darwin's theory. 



Unequal Depths of Lagoons and Banks 

 the requirements of the glacial-control theory 



It is desirable, before the facts as to the depths of lagoons and banks 

 are examined, to define as clearly as possible the unlike requirements re- 

 garding them that are demanded by the Glacial-control and the subsi- 

 dence theories. The Glacial-control theory, as set forth by Daly, recog- 

 nizes that "there has been Eecent crustal warping in certain oceanic areas 

 affected by coral reefs" (1915, 222), but places much greater weight on 

 "a long period of nearly perfect stability for the general ocean floor"; 

 this is clear from the statement : "Most of the reef platforms, like many 

 banks situated outside the coral seas, have such forms, dimensions, and 

 relations to the sealevel that they appear to have originated during a long 

 period of nearly perfect stability for the general ocean floor. . . . That 

 is a conclusion forced on the writer by a close study of the marine charts. 

 Its validity is a matter quite independent of the validity of the Glacial- 

 control theory. . . . Submarine topography seems impossible of ex- 

 planation without assuming crustal quiet beneath most of the deep sea 

 during at least the later Tertiary and Quaternary periods. The new^ 

 theory, therefore, is based on the necessity of assuming general crustal 

 stability in the coral-sea area during the formation of the existing reefs 

 and platform surfaces" (162). 



The theory then postulates a lowering of ocean level by some 30 or 40 

 fathoms during the Glacial period, the abrasion of platforms by the low- 

 ered ocean, and the upgrowth of reefs on the platform margins as the 

 ocean rose to its normal level. Little attention is paid to the replacement 

 of abrasion by reef growth during inter-Glacial epochs; it is stated that 

 "wave abrasion began before the climax of the Kansan stage and con- 

 tinued without serious interruption until the Wisconsin climax" (181) ; 

 the much longer duration and the somewhat higher temperature of the 



