YIELDING OF THE EARTHS CRUST — BOWIE. 



247 



that is yielding to horizontal stresses is a function merely of the 

 temperature, and as the temperature at any particular depth is no 

 doubt somewhat uniform around the whole earth, the depth of tran- 

 sition from resisting to yielding material can not be very different 

 for different blocks of the earth's crust, except where the geoiso- 

 therms are displaced under areas of active erosion and of active 



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Fig. 9. — Stress diagram of columns after erosion and deposition. 



After the erosion of material from a high, block and its deposition on a lower one, 

 the stress differences will be from the high block toward the low one almost down to 

 the depth of compensation. The stress differences near the lower ends of the blocks are 

 from the low block toward the high one. This is on the assumption that the isostatic 

 adjustment has not yet taken place to counterbalance the transfer of material at the 

 surface. 



sedimentation due to comparatively rapid vertical movements of the 

 material of the blocks. 



THE EARTH IS A YIELDING BODY. 



Since the material of the earth is yielding to vertical forces and 

 since the material below the earth's crust moves horizontally to re- 

 store the isostatic balance, it is appropriate to use the words of 

 Professor Hay ford and call the earth a " failing structure." I pre- 

 fer to call it a yielding body. The material of the crust and that 

 just below it must give way to comparatively small stress differences. 



