MASS DYNAMIC ACTION. 295 
It follows from the foregoing that the deformation accomplished by 
widely spaced fractures does not result in the obliteration of the original 
textures and structures, except adjacent to the fractures. The rocks are 
merely jointed, sliced, piled up, or brecciated, and in each block or slice 
the alterations are metasomatic, or those of molecular dynamic action. 
ZONE OF COMBINED FRACTURE AND FLOWAGE 
Since the metamorphism of the intermediate zone of fracture and 
flowage combines the phenomena of the zone of fracture and the zone 
of flowage, its consideration is deferred until after the zone of flowage 
is treated. 
'ZONE OF FLOWAGE 
At the outset it may be said that the process of rock flowage is very 
different from the flowage of a liquid. 
It has been explained in another place * that in the deep-seated zone of 
rock flowage the process of deformation is similar to that of mashing or 
kneading. ‘There goes icle: small or great, takes part in the defor- 
mation. 
As soon as interior movements theta the destruction of the original 
textures and structures begins and goes on very rapidly, so that with com- 
paratively little motion the original textures may be wholly destroyed. 
For instance, such rocks as quartzose sandstones, which retain their struc- 
tures for indefinite periods if there be no mass action, even when buried 
under thousands of feet of other rocks, when deformed by mashing rap- 
idly lose all clastic textures. In the same way the textures which are 
characteristic of igneous rocks rapidly disappear by mashing. In the 
place of the original textures, whether those of sedimentary or igneous 
rocks, there appear peculiar textures and structures referred to subse- 
quently as characteristic of mass dynamic metamorphism. 
During the interior mass movements of rocks water makes its way 
between the particles much more readily than under conditions of qui- 
escence. This follows partly from the movements and partly from the 
heat developed by the movements. ‘The increased temperature results in 
decreasing the viscosity of the water, and it has been seen (pages 272, 273) 
that low viscosity is of great importance in the penciration of water 
through minute spaces. 
Consequent upon interior mass movement two kinds of deformation 
occur, granulation and recrystallization. Between the two are all grada- 
tions. 
* Principles, cit., pp. 694-696. 
