216 E. A. Daly — Abyssal Igneous Injection. 



directions. The amount of creep is at a maximum above the 

 zone of injection and decreases to a minimum at certain dis- 

 tances to right and left of the middle line of the zone. 



2. This lateral creep induces a down-warp of the earth's 

 surface immediately overlying the zone of condensation. The 

 resulting geosynclinal may be the seat of v prolonged sedimenta- 

 tion. If so, the weight of the sediment itself tends to increase 

 the lateral creep in the shell of tension and the down-warp 

 slowly deepens. 



3. The shell of compression is already weakened at the 

 angles of down-warp ; it is further weakened by the sediment- 

 ary blanket which, comparatively little resistant itself, causes 

 a softening: of its basement through a rising of the isogeo- 

 therms. When the filling of the geosynclinal has sufficiently 

 thickened, the shell of compression, owing to its secular accumu- 

 lation of stresses (which are intensified by metasomatic changes 

 in the shell), begins to collapse. Mountainous forms and 

 structures result. 



4. The complete shearing apart of the shells of compression 

 and tension during the orogenic revolution releases the tensions 

 still unrelieved in the underlying shell. Abyssal injection on 

 a large scale is thus initiated or continued in the shell of ten- 

 sion. The relief of compressive stresses in the act of building 

 the mountains first occasions the possibility of magmatic stop- 

 in g and thus of the extensive assimilation of schists and sedi- 

 ments by the primal gabbroid magma. The differentiation of 

 the compound magmas of assimilation may explain the batho- 

 lithic central granites, etc. of mountain ranges, along with their 

 satellitic stocks, injected bodies and volcanic outflows. 



5. The regional warpings of the earth's crust may be partly 

 at least referred to the varying strengths of abyssal injections 

 from a fluid substratum. 



6. The location and alignment of mountain ranges, the loca- 

 tion and elongation of geosynclinals, the final development of 

 igneous batholiths and satellitic injections, are all interdepend- 

 ent and related to special zones of powerful abyssal injections 

 from the substratum. These zones are, in the large, located 

 by cosmical stresses affecting the earth along special azimuthal 

 lines. 



7. Mountain building causes relief of compressive stresses 

 in the superficial shell. The surface outflow of magma either 

 secondary or directly derived from the substratum may there- 

 fore be specially pronounced after an orogenic revolution. In 

 general, the theory of vulcanism is also fundamentally affected 

 by the doctrine of the shell of tensions which are not entirely 

 relieved by the compressive extension of that shell. 



