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



parts was the primary movement, and the apparent northeastward over- 

 thrust observed in the superficial parts is regarded as secondary and re^ex 

 in its nature. 



As shown in the two quotations given above from Suess, this was in 

 substance his original interpretation of the part played by North America 

 in the Tertiary mountain making which set the present boundaries to the 

 Pacific. He regarded the crustal sheet of North America as folded 

 southwestward toward the Pacific. Thus, on principles derived from his 

 study of Asia, Suess generalized from Eurasia to North America, and 

 concluded that the latter, like the former, had been folded toward the 

 great ocean. 



When Suess arrived at this generalization he had accomplished a great 

 and magnificent result for geology, for he showed that North America, 

 like Eurasia, had been affected in Tertiary times by a crustal movement 

 in a southerly direction — not exactly to the south, but southward with a 

 strong deflection to the west, though not more strongly than was the 

 southward movement in eastern Asia deflected toward the east. In this 

 conclusion Suess had completed in rough outline the Tertiary tectonic 

 history of the northern hemisphere. He had put both of the great north- 

 ern continents into the same category with reference to Tertiary crustal 

 movements. Eegarding each northern continent as a crustal unit, Suess 

 found that Indo-Africa had remained stationar}^, or at least without tan- 

 gential movements, but that both Eurasia and North America had been 

 affected by tangential movements in the same general direction — that is, 

 toward the south. It should be noted that in this distribution there is a 

 certain relation to latitude, for Indo-Africa, lying mainly in the tropical 

 regions, remained unmoved, while Eurasia and North America, each ex- 

 tending vast areas far to the north, both of them into the arctic regions, 

 crept away to the south. 



Here, then, is a fact as broad as the northern hemisphere. Both of the 

 only two continents whose crustal sheets reached far to the north moved 

 in the Tertiary age from north to south. Such a fact as this may be 

 taken as the concrete expression of a general law of wider scope. Thus, 

 if the forces of Tertiary diastrophism caused the earth's crust to move 

 from north to south in the northern hemisphere, may we not take this 

 distribution of the deforming force to be characteristic and fundamental? 

 Putting it in abstract form, may we not say that the deforming force 

 caused crustal creep from high latitudes toward low latitudes? But if 

 this statement expresses the truth it ought to be as applicable to the 

 southern hemisphere as to the northern, and here we are naturally in- 

 clined to turn to the antipodes to see what the evidence is there. 



