im Daly— The Coral-Beef Zone. 



The truth is that no living reef seems to have volume 

 too great to be explained by reef growth in post-Glacial 

 time, even though that time has had a duration of only 

 20,000 to 50,000 years. The more positive bearing of the 

 subject is found in the closeness of the similarity in form 

 and bulk among the reef ridges of normal atolls and 

 barrier reefs throughout the Pacific and Indian oceans. 

 The actual degree of likeness argues for a contempora- 

 neous upward shift of sea-level in the whole tropical belt 

 of the earth, just as the rough accordance of depths in 

 the larger lagoons and on rimless banks argues for a 

 former, prolonged, nearly constant relation of sea-level 

 to the submarine reliefs. 



In fact, the objection suggests another difficulty with 

 the subsidence theory. To work at all, this explanation 

 of reefs has to postulate "a long stationary period" dur- 

 ing which each lagoon floor could be flattened by aggrada- 

 tion to the observed extent. Where so many structures 

 of the kind have been developed, it would be a miracle 

 if not one "mature reef-plain' ' (completely filled lagoon) 

 of large size still remained at or near its level where the 

 plain was formed. More generally, the theory of inter- 

 mittent subsidence leads one to expect that somewhere 

 there should be reefs much broader than the average and 

 not yet sunk below the five-fathom line. But the world 

 charts fail to exhibit such very wide reefs or large 

 "mature reef -plains" at their original levels. 



7. Additional Objections. — Other strictures on the 

 Glacial-control theory have been attempted by the use 

 of data from the Funafuti and Bermuda borings, from 

 elevated "reefs" in Fiji, and from biological "proofs" 

 of enormous land bridges in the mid-Pacific, Space here 

 fails for discussion of all the points. The writer must 

 be content with the statement that none of these argu- 

 ments carries conviction. But concerning the Funafuti 

 boring a word may be added. 



According to Darwin's hypothesis of intermittent sub- 

 sidence, the Funafuti atoll mass "long" stood still, while 

 its lagoon was aggraded to a nearly level plain. During 

 that "long" time, the main reef must have grown out 

 on its own talus. Hence the lower part of the boring 

 must have passed through talus ; for, if the lagoon had 

 received enough reef debris to fill a deep "moat" around 

 a sinking volcano, the outer slope should have received 

 enough to build out a talus at least as far as the width of 



