Geophysical Abstracts 152 January-March 1953

56 GEOPHYSICAL ABSTRACTS 152, JANUARY-MARCH 1953
seismic observations, as the Sierra Nevada and the Alps have no roots and there
are even indications of the existence of anti-roots under the mountains; the
buckling hypothesis of Vening-Meinesz cannot be maintained and is not necessary
for the explanation of negative gravity anomalies in the Indian Archipelago
(Malay Archipelago) ; the convection theory of Griggs and others cannot be
maintained in view of the stratification of the earth's crust as revealed by seismic
observations; the uplift of continents may be caused by geothermal processes,
changing the volume of deeply seated formations; the crystalline crust is thicker
under the oceans; and the thickness of the plastic layers of the crust can be
determined by seismic observations of blasts. 8. T. V.
14374. Valle, Paolo Emilio. Una relazione diretta fra la velocita delle onde
elastiche e la densita nell'interno della terra [A direct relation between
the velocity of elastic waves and the density in the interior of the
earth] : Annali Geofisica, v. 5, no. 3, p. 417-431,1952.
A direct relation between the velocity of elastic waves and the density of a
homogeneous isotropic solid has been found by theoretical treatment of the
problem. The solid is supposed monoatomic and the theory applies to tem­
peratures greater than the Debye temperature.
The theory is based on the solid state equation and on the hypothesis that the
modulus of elasticity, which determines the velocities of the waves of thermal
motion, depend only on the mean distance between the particles of the solid.
The applicability of this relation to the interior of the Earth is discussed
and a comparison made between the velocity of seismic waves given by Jeffreys
and the density of Bullen. The agreement between the theory and geophysical
data is satisfactory, either for the mantle of the Earth, or for the core, to which
the theory can be extended. Author's summary
14375. Bullen, K. E. On density and compressibility at pressure up to thirty
million atmospheres: Royal Astron. Soc. Monthly Notices, Geophys.
supp., v. 6, no. 6, p. 383-401, 1952.
A critical examination is made of curves presented by W. M. Elsasser on the
density and compressibility of materials at zero temperatures and pressures up
to 30 million atmospheres, and of Elsasser's inference that the Earth's core
consists of iron or nickel iron. An argument leading Elsasser to suggest that
the writer's Earth models A and B may require adjustments because of discrep­
ancies with Elsasser's results is shown to be invalid.
New tables are presented which fit the date used by Elsasser at 30 million
atmospheres and are also consistent with geophysical data. The calculations
leading to these tables imply that the atomic number to be associated with the
material of the outer central core should be at least 6 units less than the value
derived using simple extrapolations from quantum-mechanical calculations for
high pressures. If the reduction in the atomic number is no more than 6 units,
the most probable composition of the material in question would still be nickel
iron, and to this extent Elsasser's main conclusion is supported. But there are
other aspects of the new calculations which suggest that the needed reduction
may be greater than 6 units; these aspects raise the probability that the outer
central core consists of a modification of ultrabasic rock. A caution is issued
against forming too definite conclusions on either of the 2 opposing theories on
the whole evidence so far available.