MASS DYNAMIC ACTION. 313 
cles. Thus we have all combinations of macroscopic and microscopic 
fractures and recrystallization. 
In some places the intermediate zone of combined fracture and flowage 
is broad ; in other places it is narrow. The phenomena of the zone may 
be seen in aqueous and igneous rocks alike. Many illustrations of each 
might be given. 
As typical cases of sedimentary formations altered in the zone of com- 
bined fracture and flowage may be mentioned the Wewe and Siamo slates 
_of the Lower Marquette series, and the Goodrich quartzite and the eastern 
half of the Michigamme formation of the Upper Marquette series, of the 
Marquette district of Michigan.* Within these formations almost every 
one of the multifarious reactions described, both within the zone of frac- 
ture and the zone of flowage, and many others, are beautifully illustrated. 
Indeed, it was a study of these formations which first suggested to me 
the idea of a combination of the phenomena of different alterations near 
the surface and at depth, and the very great difference in the alterations 
which occur under mass static conditions and under mass dynamic con- 
ditions. 
in Calaveras creek, a short distance below Calaveras valley, south of 
San Francisco, in the Coast ranges of California, are seen all stages of 
transition between a brecciated igneous rock and a crystalline schist. 
The first was deformed under conditions of spaced fractures. The sec- 
ond was deformed by granulation and recrystallization. In passing 
from the breccia to the schist one first finds about the blocks of igneous 
rock which have their characteristic textures, mere films of schist. Pass- 
jng farther toward the schist, an intermediate stage is found, in which 
unmashed blocks lie in a schistose background or matrix. Buta short 
distance from this place is the completely altered schist, in which no 
unmashed fragments remain. 
Every stage of the transition is seen. The alterations within the blocks 
are those of mass static conditions or those of molecular dynamic action 
(pages 287-294). Within the films and layers of crystalline schists con- 
stituting the matrix in which the blocks rest and in the main mass of 
schist the alterations are those of mass dynamic action. 
COMPARATIVE ENERGY REQUIRED FOR DEFORMATION IN THE THREE ZONES OF 
FRACTURE, FRACTURE AND FLOWAGE, AND FLOWAGE 
The question of the amount of energy required to produce deforma- 
tion in the zone of fracture,in the intermediate zone of fracture and 
flowage. and in the deep-seated zone of flowage is a matter of great im- 
portance. 
* Mon. xxviii, cit. 
