lliH) U. A. DALY METAMOUPJUSM AND ITS PHASES 



Lapparont eviflently tlioiig-ht that the term shmilrl mean much more than 

 ])iirc cm siring. 



Zirkel (1893, I, page GOl:) was of opinion that "dynamo-metamor- 

 phism/^ as denoting merely the participation of a force, is a too general 

 name. 



'I'ermier {\\)0o, page 580, and 1910, page 588) considers that dynamic 

 metajnorphism '^deforms hut does not transform," and has strenuonsly 

 advocated its disuse in scientific writing. Gruhenmann (1910, page 125) 

 also recommends its abolition, since, in his opinion, the name leads to the 

 wi'ong notion, tliat ]nere pressure suffices for the rock alterations observed 

 in mountain-built areas. Yan ITise (1904, page 7G3) holds that the term 

 is '^<)l)jectiona])le for many reasons"; that ^'fracturing in the belt of 

 cementation is equally dynamic metamorphism," and that (page 39) ^'in 

 an exact sense all metamorphism is dynamic . . . dynamo-metamor- 

 phism refers to conditions of motion." Leitli and Mead (1915, page 

 307) make "dynamic metamorphism" a rigorous synonym of "rock flow- 

 age." Similarly, Lahee (1916, page 231) regards the development of 

 schistosity at right angles to the vertical stress of mere load as one type 

 of dynamic metamorphism. 



Without further extracts from the recent literature, a serious divergence 

 of view is obvious. Termier's position can be understood only on the 

 supposition that he defined "metamorphism" in a manner iina(.;ceptable 

 to most geologists. More specifically, he does not regard new crystalliza- 

 tious as implied in the use of tliis key word; neither does he follow the 

 definition of dynamic metamorphism given by Eosenbusch and practically 

 adopted since 1889 by the majority. T'ermier's statement (1903, page 

 581) that "dynamic metamorphism . . . does not exist" depends on 

 an arbitrary and hardly defensible definition of the term. CTrulienmann's 

 olijection to it loses weight if it be recognized that "metamorphism" itself 

 im])lies the activity of solutions; the idea that pressure alone is involved 

 iu the dynamic phase is antomatically excluded. The objections by Van 

 Ilisc and Zirkel, founded on a too inclusive use of the word "dynamic," 

 have already been discussed; all progress in classification is im]:)eded if 

 tlie meaning of adjectives or noun be fixed by literal etymology. 



How far such a technical expression as "dynamic metamorphisju" l)ears 

 its meaning on its face depends on the meaning to be assigned to its 

 correlative or negative in scientific classification — in this case, "'static 

 metamorphism." In the miud of the average geologist using both terms 

 is a more or less distinct picture of the thing whicli "moves" or "stands." 

 That thing is the earth's crust. One set of metamorphic conditions ac- 

 companies strong movements of the crust. Another, not necessarily quite 



