186 F. B. TAYLOR ORIGIN OF THE EARTH's PLAN 



peripheral mountain belt with which we are here most concerned, Suess 



"A great part of this folding is of recent age, or has been continued into 

 very recent times; it is not certain that the movement has ended" (I, 597). 



And in the summary of his chapter on the relations of the Alps to the 

 mountains of Asia, he says : 



"Thus we see that since the Middle Tertiary period, and up to still more 

 recent times, important tangential movements have taken place, and have 

 thrown into folds a sea-bottom which extended through the middle of Europe 

 and Asia" (I, 507). 



The ranges here referred to were formed out of sediments laid down in 

 the ancient greater Mediterranean, which Suess calls the Tethys, and of 

 which the modern Mediterranean Sea is only a remnant. 



Thus, in brief, Suess finds Eurasia to be a great unit of continental 

 growth which has advanced to its present state by well defined steps from 

 early, smaller beginnings in the far north. First, there was the ancient 

 "vertex'^ in Siberia. This is an ancient plain, marking the planed-down 

 surface of still more ancient rocks, which, through all the steps of conti- 

 nental development since pre-Cambrian times, have remained remark- 

 ably stable and free from disturbance. This plain has not been folded 

 by any of the Paleozoic or later folding movements which have brought 

 into being the great mountain ranges that run in concentric lines around 

 its southeastern, southern, and southwestern sides. Through very long 

 periods of relative quiet, sediments accumulated in the border of the sea 

 surrounding the vertex. Then in relatively short periods of diastro- 

 phism or crustal deformation these sediments were squeezed and thrust 

 horizontally in southerly directions — that is, toward the sea — and folded 

 into the mountain ranges. This cycle of continental growth was repeated 

 three times, and produced successively in three periods of folding the 

 three principal mountain systems which characterize Eurasia. In the 

 beginning there were several smaller separate continental elements, and 

 they were not welded together into the one great continental unit of 

 Eurasia until the last or Tertiary folding period. It was this last and 

 by far the greatest of the mountain-making periods since pre-Paleozoic 

 times that brought Eurasia to its present state. 



Figure 2 shows the trend lines of the Tertiary fold-mountains of Eu- 

 rasia. The older lines are omitted. The shaded parts, comprising the 

 peninsulas of India and Arabia and part of Africa, represent the ob- 

 structive fragments of the ancient Indo- African continent against which 

 the southward folding of the western half of Eurasia was thrust. . 



