808 EEroRT— 1892. 



lines of the Atlantic. The highly folded strata of the Atlantic sea-board are the 

 relics of great mountains of upheaval, the origin of which cannot be assigned to a 

 more recent date than Paleozoic times. During subsequent crustal movements 

 no mountains of corrugated strata were nplifted along the Atlantic margins, the 

 Mesozoic and Cainozoic strata of the coastal regions showing little or no disturb- 

 ance. It is quite in keeping with all this that volcanic action appears to have been 

 most strongly manifested in Palseozoic times. So many long ages have passed 

 since the upheaval of the ArchaBan and Palaeozoic mountains of the Atlantic sea- 

 board that these heights have everywhere lost the character of true mountains of 

 elevation. Planed down to low levels, partially submerged and covered to some 

 extent by newer formations, they have in many places been again converted into 

 dry lands, forming plateaus — now sorely denuded and cut up into mountains and 

 valleys of erosion. "Why the later movements along the borders of the Atlantic 

 basin should not have resulted in the wholesale plication of the younger sediment- 

 ary rocks is a question for geologists. It would seem as if the Atlantic margins 

 had reached a stage of comparative stability long before the grand Tertiary uplifts 

 of the Pacific borders had taken place ; for, as we have seen, the Mesozoic and 

 Cainozoio strata of the Atlantic coast-lands show little or no trace of having been 

 subjected to tangential thrusting and crushing. Hence one cannot help suspecting 

 that the retreat of the sea during Mesozoic and Cainozoic ages may have been due. 

 rather to subsidence of the oceanic trough and to sedimentation within the con- 

 tinental area than to positive elevation of the land. 



Over the Pacific trough, likewise, depression has probably been in progress 

 more or less continuously since Palieozoic times, and this movement alone must 

 have tended to withdraw the sea from the surface of the continental plateau in 

 Asia and America. But by far the most important coastal changes in those 

 regions have been brought about by the crumpling up of the plateau, and the for- 

 mation of gigantic mountains of upheaval along its margins. From remotest 

 geological periods down almost to the present the land area has been increased 

 from time to time by the doubling-up and consequent elevation of coastal accumu- 

 lations and by the eruption of vast masses of volcanic materials. It is this long- 

 continued activity of the plutonic forces within the Pacific area which has caused 

 the coast-lands of that basin to contrast so strongly with those of the Atlantic. 

 The hitter are incomparably older than the former, the heights of the Atlantic 

 borders being mountains of denudation of vast geological antiquity, while the 

 coastal ranges of the Pacific slope are creations but of yesterday as it were. It 

 may well be that those Cordilleras and mountain-chains reach a greater height 

 than was ever attained by any I'ahneozoic uplifts of the Atlantic borders. But the 

 marked disparity in elevation between the coast-lands of the Pacific and tho 

 Atlantic is due chiefly to a profound difl'erence in age. Had the Pacific coast- 

 lands existed for as long a period and sufi'ered as much erosion as the ancient rocks 

 of the Atlantic sea-board, they would now have little elevation to boast of. 



The coast-lines of the Indian Ocean are not, upon the whole, far removed from 

 the margin of the continental plateau. The elevation of East Africa for 6,000 feet 

 would add only a very narrow belt to the land. This would still leave Madagascar 

 an i.sland, but there are geological reasons for concluding that this island was at a 

 lar distant period united to Africa, and it must therefore be considered as forminf^ 

 a portion of the continental plateau. The great depths which now separate it from 

 the mainhiud are probably due to local subsidence, connected with volcanic action 

 in Madagascar itself and in the Comoro Islands. The southern coasts of Asia, like 

 those of East Africa, approach the edge of the continental plateau, so that an ele- 

 vation of 6,000 feet would make little addition to the land area. With the same 

 amount of upheaval, however, the Malay Peninsula, Sumatra, Java, and West 

 Australia would become united, but without extending mucli further seawards. 

 Land connection, as we know, existed in Mesozoic times between Asia, Australia, 

 and New Zealand, but the coast-lines of that distant period must have differed 

 considerably from those that would appear were the regions in question to experi- 

 ence now a general elevation. The Archfean and Palieozoic rocks of the Malay 

 Peninsula and Sui^atra are flanked on the side of Ihe Indian Ocean by great 



