BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 18, pp. 233-250, PL. 5 JUNE 5, 1907 



OEIGIN OF OCEAN BASINS IN THE LIGHT OP THE NEW 



SEISMOLOGY* 



BY WILLIAM HERBERT HOBBS 



(Bead before the Society December 28, 1906) 



CONTENTS 



Page 



Usual ai'guments for antiquity of present ocean basins 233 



Supposed absence of continental rocks from oceanic islands 234 



Abnormal gravity within infra-continental zones 234 



General absence of deep-sea deposits from continental areas 235 



Significance of f aunal and floral distribution 235 



Former intercontinental regions 236 



Symmetry about the north Atlantic 238 



Modern view of bradysisms 239 



The ocean basins of the secondary era 241 



Distribution of seaquakes and tsunamis 242 



Fractures of under-sea cables at time of earthquakes 243 



Forster's observations on sudden changes in the Mediterranean floor 244 



Contrast of movements of crustal blocks within the continental and under- 

 sea areas 246 



Modern seismology and fundamental conceptions of geology 247 



Crustal block movements within the coral seas 248 



Isostatic adjustment 249 



Great oceanic revolutions and geological periods 249 



Usual Arguments for Antiquity of present Ocean Basins 



The doctrine that the present ocean basins came into being at an early 

 stage of the earth's history we owe especially to James D. Danaf and 

 Charles Darwin,! though there have been many followers. The facts 

 and supposed facts on which this theory was founded have for the most 

 part either been modified or given a different interpretation during the 

 time which has since elapsed. Moreover, the new seismology — the study 

 of earthquakes from a distant station — seems now to be furnishing new 



* Manuscript received by the Secretary of the Society March 2, 1907. 



t Am. Jour. Sci. (2), vol. 2, 1846, p. 352. Manual of Geology, sixth ed., pp. 815-817. 



X Origin of Species, first ed., p. 343. 



XX — Bull. Geol. See. Am., Vol. 18, 1906 (233) 



