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continents as we have established them by the Precambrian fold 

 directions and other evidence. This is especially clear in the case 

 of the boundary between Eurasia and Gondwana. 



The earthquake tracts distinctly form a latitudinal belt (also 

 known as " Libbey's circle ") around the earth, separating North 

 and South America, traversing the middle Atlantic and separating 

 first Eurasia from Africa and then from the .other Gondwana elements 

 (India, Arabia and western Australia) and reaching again across 

 the middle Pacific to Central America. 



Another belt follows the eastern, northern and western boundaries 

 of the Pacific ocean. It seems to be completed by the Antarctic 

 seismic regions, as suggested on the chart. There are further known 

 independent shorter longitudinal tracts in the Atlantic and Indian 

 oceans, that indicate that the forces active along the later zones 

 of fracturing which led to the breaking down of the eastern part 

 of the old " Atlantis," and the separation of Gondwana into three 

 continental portions, have not yet become extinct. 



When we go backward from Recent and Tertiary times to the 

 Mesozoic age, we find in the geosynclines as reconstructed by Haug 

 (see fig. 5) for that era, an expression of the same mobile tracts, 

 with the addition of a northern loop separating Asia and Europe. 



[Fig. 5 Chart of geosynclines in Mesozoic time — From Haug (1900). 



