102 C. Suhuchert — Problem of Continental Fracturing 



Origin of the Ocearddes. — Finally, we must ask, When did 

 the thousands of oceanic islands — the Oceanidcs — arise? They 

 occur singly, in groups, and most abundantly in linear arrange- 

 ment. The isolated and the grouped islands probably all repre- 

 senl great volcanic cones that have built themselves up from 

 flu' ocean bottom through the eruption of rock material. What 

 is the origin, however, of those that are arranged in linear 

 series '. Are they ranges of volcanoes that have likewise grown 

 from the depths but are situated on lines of fracture in the 

 lithosphere, or do they rest on the crests of great arches or 

 foldings of the ocean bottoms? Equally important questions 

 are : What is their geological history, and have they simul- 

 taneous or successive origins ? So far as known, none of the 

 smaller oceanic islands reveals fossils older than the later Ter- 

 tiary, a condition that appears to be in harmony with the theory 

 that the sum of their movements is negative and thus in keep- 

 ing with the idea that the oceanic bottoms are in the main sub- 

 siding areas. Because of the fact that in the oceans volcanic 

 mountains and folded mountains are protected from erosion 

 by the covering of water, they, unlike the ridges of the dry land, 

 last from one era to another. In fact, the submerged ridges 

 lying at depths of less than 10,000 feet will be built up through 

 the rapid accumulation of organic calcareous debris, while the 

 abysses on either side will receive little solid matter, because of 

 the great solvent power of the water of the deeper parts of the 

 ocean. In the words of Suess 7 : "The result is an exaggera- 

 tion of the relief." Because of the inaccessibility of the sub- 

 merged parts of the Oceanides, we have as yet little evidence 

 showing when they originated, and yet on the basis of the 

 periodically recurring diastrophism it would seem that none is 

 older than the Permian, a time of intense and world-wide 

 crustal deformation. Others may have originated during the 

 late Cretaceous crustal movements, and all may have again been 

 reelevated and stirred into volcanic activity with the world-wide 

 crustal readjustments that began in the Miocene and continued 

 into late Pliocene time. 



Some objections to continental fracturing. — The views just 

 presented are those of most paleontologists, but there are geolo- 

 gists and zoogeographers who do not accept the idea of conti- 

 nental fragmentation taking place on so large a scale as is here 

 indicated. They hold firmly to the theory of the permanency 

 of continents and ocean basins, believing that these positive and 

 negative elements of the earth's surface have always retained 



7 Ed. Suess, Face of the Earth, vol. iv, p. 326. 



