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DALY. 



of central faros not killed during the lately renewed submergence? 

 The first question is directly answered by the Glacial-control theory; 

 the second presents a residual problem which is not vital to the newer 

 theory. 



Finally, it may be recalled that many wide banks far outside the 

 coral seas have roughly accordant and nearly uniform depths of 45 

 to 90 m. — of the same order of magnitude as the depths in the wider 

 lagoons and on unrimmed banks within the coral seas. Evidently the 

 "long pause" in subsidence must be considered in the case of the 

 extra-tropical banks also. However, these were not formed by coral 

 growth and it is generally agreed that they are due to abrasion and 

 concomitant shelf-building by waves and currents. Two totally 

 different causes thus produce, in each of the broad oceans, banks that 

 accord in depth. If the unrimmed Padua bank (Fig. 37) has similar 

 depth because it has shared in the sinking of neighboring atolls 

 (Darwin's view), it is as logical to assume that all the great banks 



Figure 44. Composite copy of Darwin's sections illustrating his subsidence 

 theory. Successive sea-levels at L, L', and L"; fringing reefs at F; barriers 

 at B; atoll reefs at A . 



showing similar depths have likewise subsided, and to practically the 

 same amount. The incredible nature of that conclusion needs no 

 emphasis. 



The subsidence theory is not simple, as so often claimed. Because 

 of the improvement in ocean charts since Darwin's day, the necessity 

 of postulating an extremely long pause in subsidence is now clearer 

 than ever, if this theory is to be saved at all. In other words, the 

 accessory assumption of very prolonged crustal stability really ex- 

 plains much more of the intertropical topography than does the chief 

 postulate of crustal instability. Related assumptions are: that the 

 renewal of sinking was essentially synchronous throughout the reef 

 areas; and that this sinking, in the same vast regions, was very nearly 

 uniform in amount. Compared to an explanation so complicated, the 



