216 



by the Tertiary tangential movements. Its crustal movement was de- 

 flected to the west even more strongly than was that of j^orth America — 

 more strongly than any other continent, unless it be the New Zealand part 

 of the Australian sheet (see figure 7). Only in the extreme northern 

 part was the movement northward. A part of its Tertiary chains in 

 Peru and Bolivia trending northwest and southeast were thrust from the 

 northeast, and have therefore been deflected more than 90 degrees from 

 the normal south-to-north direction, and the same is the case with New 

 Zealand. The great arc of the northern Andes, extending from Vene- 

 zuela to northern Chile, is convex toward the west — that is, toward the 

 Pacific. 



Here again the Cuzco knot of the Andes, one of the most remarkable 

 mountain knots in the Avorld, is somewhat interlobate in character — that 

 is, it is in a re-entrant angle, where the crustal movements were slightly 

 convergent, though less so than in Alaska. The Alps of New Zealand 

 appear also to l)e at an angle of convergence or intersection. 



The most peculiar character in South America, however, is the curva- 

 ture of its Cordillera to the east at the southern extremity. It is as 

 though the folds of the main Cordillera, being pushed toward the west, 

 had lagged or dragged behind the rest at the extreme southern end. If 

 this be true, it appears to indicate a minimum movement of 400 or 500 

 miles, which compares favorably with the movement of North America, 

 as indicated by the rift of the Labrador Sea. 



The curved ranges of the Antilles lie in the region of conflict between 

 the two Americas, just as the irregular ranges of Europe lie between 

 Europe and Africa and the peculiar mountain forms of Borneo, Celebes, 

 and Halmahera lie between Asia and Australia. But the movements of 

 the two Americas did not meet squarely, nor was one much more vigorous 

 than the other. Both being relatively weak, there was an easier adjust- 

 ment on curves of broader sweep. Nevertheless, the magnificent curve 

 of the lesser Antilles reminds one of the sharper curves in Europe — the 

 Eoumanian, Alpine, and Betic arcs— and still more of the sharp curves 

 of the Java and Timor lines, where they turn in such remarkable curves 

 from east to north and back to the west to the island of Ceram (see 

 figure 2). Even if the explanation of the plan of these ranges be re- 

 garded as still problematical, it is easy to see that they all occur in re- 

 gions where there was a conflict of crustal movements and a tendency to 

 a tangling and complication of folds. 



THE MID-ATLANTIC RIDGE 



One of the most remarkable and suggestive objects on the globe is the 

 mid-Atlantic ridge. It is well shown on Sir John Murray's bathymetri- 



