THE GEOLOGICAL ASPECTS OF THE 

 CORAL-REEF PROBLEM 



By Prof. W. M. DAVIS, Ph.D., Sc.D., 



Harvard University, Cambridge, Mass., U.S.A. 



CONTENTS 





Dana's Confirmation of Darwin's Theory . 

 Exclusion of Still-stand Theories 

 Distinction between Subsidence and Submergence 

 Unconformable Contact of Reef Limestones and their 



Foundations 



Origin of Elevated Reefs 



Inattention to Embayments and Unconformities 

 Semper on the Reefs of the Pelew Islands 



Rein on the Origin of Atolls 



Murray on Atolls and Barrier Reefs . 



Wharton on the Truncation of Atoll Foundations 



Inadequate Treatment of the Coral-reef Problem 



Instability of Scientific Opinion . 



Verification of Coral-reef Theories . 



The Reefs of the Seychelles .... 



Darwin's Theory of Intermittent Subsidence 



The Origin of Atolls 



The Glacial-control Theory .... 

 Molengraaff's Theory of Subsiding Volcanic Islands 



PACE 



420 

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423 

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433 

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442 

 442 

 443 



Dana's Confirmation of Darwin's Theory. — The old coral-reef 



problem gained a new attraction for me some twenty years 



ago, when the embayed shorelines of the reef-encircled volcanic 



islands in the Pacific were recognised as giving independent 



support to Darwin's theory of upgrowth during intermittent 



subsidence ; but it was only about five years ago that I learned 



how clearly Dana had in 1849 made explicit announcement of 



this physiographic evidence for subsidence and how generally 



the evidence had been overlooked by others, including Darwin 



himself. True, Penck had in 1 896 perceived that the embayed 



shoreline of Queensland, as represented on large-scale charts, 



proved a submergence of the coast in association with the 



formation of the Great Barrier Reef in front of it ; and Andrews, 



420 



