ORIGINAL ARTICLES. 



A Recent Worldwide Sinking of Ocean-level 



By Reginald A. Daly, Harvard University, Cambridge, 

 Massachusetts. 

 Introduction. 

 Field Observations. 



First Contact with the Problem. 



Gulf of St. Lawrence. 



Maine. 



Samoa. 



Difficulties of an Inductive Study of Records. 



British Isles. 



Atlantic Coastal Plain of the United States. 



Florida Ke3^s and West Indies. 



South America. 



Graham Land. 



New Zealand. 



Australia. 



Pacific Islands. 



California. 

 Amount of the Eustatic Change. 

 Contemporaneity and Age of the Strands. 

 Cause of the Eustatic Change. 

 Conclusion. 



T OCAL uplift and local sinking of the earth's surface have been 

 -■-^ fully demonstrated Jor j)ast geological epochs. The amounts 

 of these movements have generally been stated with reference to 

 the present sea-level, and for the greater movements the statements 

 of magnitudes are not seriously impaired by the fact that general 

 sea-level itself has been shifting, upwards and downwards, through 

 geological time. Among the causes for general or " eustatic " 

 shifts of sea-level are : appropriate crustal movements whereby 

 the volume of the ocean basin has been changed ; delta-building 

 and volcanic eruption on the sea-floor, the displacement of sea-water 

 not being compensated by crustal sinking ; volcanic addition of 

 new water to the ocean ; subtraction of water which becomes 

 chemically bound during the alteration of rocks ; glaciation on land, 

 lowering sea-level by the abstraction of water from the ocean ; 

 deglaciation on land, raising sea-level ; changes in the earth's 

 centre of gravity and in her speed of rotation.^ 



Numerous as these possibilities are the proof of a eustatic change 

 in shore-levels is not easy. In the following pages are recorded some 

 field facts which suggest the probability of a sinking of general sea- 

 level to the extent of about 20 feet during the human period. The 



^ The writer has recently found that A. Tylor (Geol. Mag., 1868, p. 576, 

 and 1872, j). 392) anticipated even Belt in relating the origin of coral reefs 

 to the shift of ocean-level consequent on deglaciation. W. B. Wright (The 

 Quaternary Ice Age, London, 1914, p. 417) believes the submerged forests of 

 the British Isles prove a eustatic shift of 55 to 60 feet, if not of considerably 

 greater amount, and attributes it to deglaciation. 



