180 F. B. TAYLOR ORIGIN OF THE EARTH^S PLAN 



belt comprises the entire Pacific coast of the two Americas and of Asia 

 and extends westward along the southern border of Asia and Europe to 

 the Atlantic coast in Spain and Morocco. In the Malay archipelago the 

 belt branches to the eastward and sends an arm around the northern and 

 eastern sides of Australia, but the mountain ranges of this branch are 

 mostl}^ submerged, and are now represented only by island chains, in- 

 cluding New Guinea, New Caledonia, New Zealand, and many smaller 

 islands. Excepting the gap between New Zealand and southern Chile, 

 the Pacific Ocean is completely surrounded by the Tertiary mountain 

 belt. This fact rests upon a sound basis of observations, and is one of 

 the most comprehensive and deeply significant things which mankind 

 has yet learned with certainty concerning the development of the earth. 

 The Tertiary moimtain belt is a large element in the earth^s plan, and a 

 satisfactory explanation of its origin is a desideratum of the first order. 



Under the various forms of the contraction hypothesis of mountain 

 making, this mountain belt has been ascribed to horizontal thrust move- 

 ments directed from the ocean toward the land. The cause assigned is 

 subsidence of the earth segment which underlies the ocean — a conse- 

 quence following, according to some, upon secular cooling and contrac- 

 tion, and this has been the dominant view; but upon planetesimal set- 

 tling and solidification, with some cooling and contraction, according to 

 others, and upon original differences of density, with molecular changes 

 and expansion, producing deep-seated movements from the oceans toward 

 the continents, according to still others. 



The remarkable relation of the Tertiary mountain belt to the Pacific 

 Ocean is the thing which is usually most emphasized in discussing the 

 origin of these mountains, and principles based on the supposed meaning 

 of this relation have been applied to other mountains as well, for it is 

 claimed that the relation indicates an oceanic cause which is general in 

 its application. But the fact should not be overlooked that this same 

 mountain belt forms an important part of the periphery of all the conti- 

 nents excepting Africa, and since the belt as a whole falls naturally into 

 divisions or parts corresponding to the several continents to which it has 

 peripheral relations, the question arises as to whether these parts may 

 not be causally related to their associated continents rather than to any- 

 thing in the oceanic areas. 



The several continental divisions of the belt show characters which 

 seem to correspond roughly to continental magnitudes. For example, 

 Asia, or, more accurately, Eurasia, with small parts of northern Africa 

 and Alaska, stand together structurally as one continental unit and con- 

 stitute by far the greatest of the continental bodies. Asia proper is the 



