Earth contraction and mountain building (I), etc. [untitled DSc]

Earth contraction and mountain building (I)

The surface flow of heat at present is probably less than has been assumed by some recent writers. The actual value may not be far from 1.633 x 10 -6 cal. sec. -1 cm. -2, the British Association figure. If it had not been for the recent glaciation the amount would have been larger, but probably not more than about 2 X 10 -6 cal. sec. -1 cm. -2. The low value is in favour of low crustal temperatures, such as are assumed by supporters of the Contraction Theory, but other considerations are against this. Reasons may be given for presuming that the "granitic layer" of the earth's crust has somewhat the same composition as the Scottish Lewisian Gneiss. It must in that case have a lower radioactive content than normal granite. The sedimentary layer which overlies it is in places at least 6 km. in thickness, and this layer is also poor in radioactive constituents. By an apparent paradox, these facts make it possible to deduce higher temperatures for the deeper continental layers.

Earth contraction and mountain building (II)

The resistance of rock -masses to very long - continued pressures is at present unknown, and it cannot be tested in the laboratory. If the Contraction -Theory is true, the upper layers of the earth's crust must be able to resist a very large stress for millions of years, without being deformed beyond the elastic limit. These layers must however "creep" over a substratum which can only have about a thousandth part of the strength which exists above. This is a necessary inference, which appears to tell against the validity of the theory.

The Dynamics of Faulting; The geology of the schists of the Schichallion District (Perthshire); The path of a ray of light in a rotating homogeneous and isotropic solid.