CONDITION OF WATER IN ZONE OF ANAMORPHISM. 659 



slabs at the surface without rupture, the most notable beiug that of an 

 upright marble slab, 3.35 meters long, 22.8 cm. wide, and 6.35 cm. thick, in 

 one of the doors of the Alhambra, Spain, which, through the settling of the 

 material of the wall, had attained a curvature of 76.2 mm." 



From these illustrations it appears that a strong force rapidly applied 

 may deform a rock by fracture, whereas a very moderate force slowly 

 applied may deform it by fiowage. This principle probably has great 

 geological significance in metamorphism. Where the deformation is very 

 rapid the zone of fracture and the alterations of the zone of katamorphism 

 may extend to great depth. Under such circumstances igneous injection 

 and cementation may go on, but as soon as the earth movements cease, or 

 lessen in speed, the openings are gradually closed by rock fiowage under 

 the laws of the zone of anamorphism. Thus a great zone or belt of rocks 

 is alternately under conditions of the belt of cementation and under condi- 

 tions of the zone of anamorphism, according as deformation is fast or slow. 

 This subject will be further considered on subsequent pages, especially in 

 the section on pegmatization. (See pp. 720-728.) 



CONDITION of water. 



In considering the condition of water in the zone of anamorphism the 

 temperature is of the utmost importance. It has been explained on page 

 566 that above a temperature of 365° C, the critical temperature of water, 

 water can exist only as gas. Supposing the increment of increase of tem- 

 perature with depth to be 1° C. for 30 meters, this temperature would be 

 reached at a depth of 10,950 meters, even if the temperature be 0° C. at 

 the surface. It has been explained that the upper surface of the zone of 

 anamorphism is probably in most cases at a depth not greater than one-half 

 of 10,950 meters. It therefore is clear that in the upper part of the zone of 

 anamorphism the water may be in the form of heated liquid, not as water 

 gas. Disregarding igneous rocks and orogenic movements, where the 

 critical temperature is not reached, even if the water were at temperatures 

 far above the boiling point at the surface, the water would be held in the 

 form of liquid by the pressure, as fully explained on pages 566-569. In 

 so far as the water is in the form of liquid, nothing further need be said 



«Julien, A. A., The durability of building stones, etc.: Tenth Census of United States, 1880, vol. 

 10, 1884, pp. 366-367. 



