PRIMARY FRACTURE PATTERN 



163 



ture lines, and that these "run in the entire region often approximately 

 meridional, generally, however, northeast-southwest or northwest-south- 

 east, and only rarely east-west" (see 



figure 36). These two dominating y^-^ (// V, \ 



directions in the diagonal system "^-^ fL/^^^^^'^^^^^— \ V 



are strikingly brought out by two 



strong lines of volcanoes — the Cam- ^ y^^^?^'--^^ \Pead5ea 

 eroon fissure bisecting the Gulf of 

 Guinea and the Saint Pauls Kocks — 

 Saint Helena line."^" 



THE PRIMARY FRACTURE PATTERN 

 OF THE EARTH'S SHELL 



From what has been said in the 

 foregoing sections, it is evident that 

 the repeating patterns of relief and 

 of structure which are encountered 

 in difi^erent parts of the same conti- 

 nent, and in different continental 

 areas as well, are in reality but one, 

 of which, however, some of the four 

 component lineament series may 

 locally be either wanting or but 

 faintly indicated (see figure 30, 

 page 157). This recognition within 

 the fracture complex of the earth's 

 outer shell of an unique and rela- 

 tively simple fracture pattern, com- 

 mon to at least a large portion of 

 the surface, obscured though it may 

 be in local disU^icts through the 

 superimposition of more or less dis- 

 orderly fracture complexes, must be 

 regarded as of the most fundamental 

 and far-reaching importance. It 

 points inevitably to the conclusion 

 that more or less uniform conditions 

 of stress and strain have been com- 

 m,on to probably the earth's entire 

 outer shell. 



FiGURio 36. — Oriented Drainage and Struc- 

 ture Lines of East Central Africa 



(After Suess) 



""^ See Proceedings of the American Philosophical Society, vol. 48, 1909, pp. 22-23. 



