322 



C. SKOTTSBERG 



growing accumulation of evidence that the Pacific basin shows unique features which 

 are not duplicated in any other oceanic or continental area of the earth. There is no 

 feature on the surface of the earth which compares in dimensions and importance with 

 the Marshall line, within which the younger eruptive rocks are basaltic rather than 

 andesistic. This discontinuity in the material of the crustal layers is called here the 

 l)Oundary of the Pacific Basin. 



This is in conformity with what I have quoted above from other sources. 

 However, 



certain areas of the Pacific Ocean (near its borders, for example), at least part of the 

 region between SoutJi America and the Easter Island rise, or between the Marianas 

 and the Asiatic continent, show indications of continental layers. For the latter, petro- 

 graphical and geophysical evidence agree. 



As seen on the map, GUTEXBERG goes a good way beyond the Juan Fer- 

 nandez-San Ambrosio rise, but the Easter Island shield which, excepting the vi- 

 cinity of this island, is covered by very deep water, belongs to the wide basaltic 

 centre, where continental layers are lacking — in contrast to the Atlantic where 

 "granitic layers of the continents continue far out under the bottom . . . probably 

 at least some continental rocks underlie its bottom throughout its area". 



Turning to the speculations of biologists I shall quote some representatives 

 from the two opposite camps. Arldt {S) did not draw his conclusions merely 

 from facts of distribution but compiled a wealth of geological, palaeontological, 

 bathymetrical dates and so on, and constructed a series of maps illustrating tiie 

 distribution of land and sea through earth's history. A Cretaceous Oceania united 

 South America with Australia + New Zealand, it disappeared during Eogene and 

 left the west coast of South America in the same position as to-day. From what 

 he says about Juan Fernandez it appears that he regarded these islands as con- 

 tinental (see below p. 376), while still admitting the possibility of oversea migra- 

 tion from the coast. Campbell was for a long time a supporter of the land-bridge 

 theory. He regarded the Hawaiian Islands as formerly much larger and more closely 

 connected with land masses to the southwest, having become isolated during 

 early Tertiary time coincident with the uplift of the great Cordilleras (^^). Later, 

 when discussing the Australasian element in the Hawaiian flora he expresses him- 

 self very positively: "We are justified in assuming the former existence of land- 

 masses of considerable size, connecting more or less directly both Australia and 

 New Zealand with Hawaii" (^5.221); and when, for the third time, he took up 

 the history of the Hawaiian f^ora, he expressed himself as follows {^6. 181): 



We may assume that the Hawaiian Archipelago, as it now exists, is but a remnant of 

 a much larger land-mass which has been in subsidence for a long period, and that extensive 

 subsidence has also occurred throughout Polynesia, and to a lesser degree in Australasia. 

 One argument for this assumption is the great development of coral reefs in the Pacific, 

 especially in Polynesia and northeastern Australia. The existence of active coral reefs 

 involves continuous subsidence and the absence of large land-masses in mid-Pacific, with 

 the innumerable small coral islands and reefs, can be explained most satisfactorily on the 

 theory that the latter are remnant of submerged land-masses of large size — possible even 

 of continental dimensions. 



