930 A TREATISE ON METAMORPHISM. 



conceived as riding quietly forward toward the uplift without marked 

 deformation. 



Applying this theory, we may imagine that the Kaibab Plateau, for 

 instance, on either side flanked by a monocline, represents an uplift which 

 is produced by deep-seated shear from either side toward the plateau, 

 producing simultaneously a cleavage or a tendency toward a cleavage in 

 the zone of flowage. Such cleavage would dip away from the plateau on 

 each side of it. The joint and fault deformations exhibited by the mono- 

 clines in the zone of fracture represent the equivalent necessary superficial 

 deformation. 



Where the folds of a mountain range are symmetrical and upright it 

 would be necessary to suppose that there was an equal amount of deep- 

 seated shearing on each side toward the mountain mass. Where the axial 

 planes of the structures of the mountain masses tend to dip in one direc- 

 tion more than in another it is to be supposed that the preponderant 

 movement came from the direction in which the axial planes dip. 



Possibly the suggestion of recrystallization shearing in the zone of rock 

 flowage also has a bearing upon the importance of the tidal forces in 

 producing deformation. It has been noted that in America the eastward- 

 dipping monoclinal cleavage tends to preponderate over the westward- 

 dipping cleavage. The same is true for monoclinal folding. This is 

 especially marked for the eastern United States and Canada. How far it 

 is true over the extensive areas of pre-Cambrian rocks of central Canada 

 is uncertain. Whether in other continents there is a preponderance of 

 eastward-dipping cleavage over westward, and of monoclinal folding with 

 eastward-dipping axial planes over the reverse, I do not know and have 

 been unable to ascertain ; but it is interesting to note that if these easterly 

 structures are preponderant they are in the right direction to be genetic- 

 ally connected with tidal friction. The earth in its rotation upon its axis 

 from west to east produces a westward-moving tide. The same force which 

 acts upon the water acts upon the rocks below, or, in other words, tends 

 to slip the outer shell of fhe earth over the deeper shells. Such slipping, 

 if it takes place through the processes of recrystallization in the zone of 

 rock flowage, would produce an eastward-dipping monoclinal cleavage and 

 monoclinal folds with eastward-dipping axial planes. 



