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TERENCE T. QUIRKE 



members fail near their ends probably due to the fact that forces 

 are not transmitted well through partly deformable members. 

 The condition of a single member may be represented as in Figure i, 

 in which it is indicated that the thrust decreases from a maximum 

 at the edges of the continental and oceanic segments to a minimum 

 near their centers. Part of the force is absorbed in minor defor- 

 mation of the member and only part is transmitted; therefore, 

 the increase of force toward the end of the members is not one of 

 arithmetical progression. Thus the yielding of the earth's crust 

 permits the stresses relief, so that at one time the intensity of 



Fig. I. — Diagram to illustrate the supposed distribution of transmitted crustal 

 stresses. The top line is supposed to represent graphically the magnitude of the 

 transmitted stresses. The transmitted stresses vary from a minimum near the 

 centers of the oceanic and continental segments to zones of maximum intensity near 

 the borders of the continents. 



thrust on one side of a yielding section is much greater than the 

 intensity of thrust on the other side of the yielding section. This 

 condition results in a movement of part of the member in the direc- 

 tion of the lower intensity of thrust. This direction of movement 

 is commonly said to be the direction of the deforming force. How- 

 ever, action and reaction being equal and opposite, the direction 

 of any force must be two-faced. But whatever the direction of 

 movement, either toward or from the continental masses, the 

 continental masses exert just as great a thrust upon the oceanic 

 masses as they bear themselves. Consequently there must be 

 a tendency for the oceanic masses to suffer deformation, 

 especially near the continents. There is supposed to be a region 

 or band of great stress at the borders both of oceanic and conti- 

 nental masses, within which major deformation should be expected. 



