Equations of state of the Earth

Abstract

INTRODUCTIONThe major results of research in the United States for 1971-1974 in the areas of static, high-pressure X ray, ultrasonic and shock wave measurements, and progress in theoretical equations of state are summarized. This 4-year period has seen the massive accumulation of new data pertinent to describing the properties, and to some extent geodynamic processes, of the upper mantle as well as exposing the gauntlet of scientific challenge with regard to our lack of detailed understanding of the major changes in crustal seismic velocities, which seem to offer so much promise for earthquake prediction. In the area of very high pressure geophysics, another challenging problem uncovered is the question of explaining the low adiabatic gradient in the outer core, which seems to be required to retain liquid iron alloy material at the melting point. Important advances in what until recently has been quite empirical elastic moduli 'systematics' have demonstrated how ionic radii and ionic packing densities may be quantitatively employed to predict unmeasured equations of state as well as tie together an ever increasing body of data for the elasticity of compounds which are crystal-chemical analogs of mantle minerals. The lack of suitable pure and mechanically homogeneous samples has continued to offer a serious obstacle to the study of candidate materials of the earth's interior. When samples of critically important minerals have been synthesized in such laboratories as those of A. E. Ringwood and R. Liebermann (Canberra) and S. Akimoto (Tokyo), significant new experiments and, shortly thereafter, theoretical results have been forthcoming. Several scientific meetings and meeting proceedings published in the years 1971-1974 have included contributions from the United States and have focused on the presentation of new data and theoretical interpretations. Two symposia of the International Association of Seismologists and Physics of the Earth's Interior (IASPEI) were organized at the fifteenth meeting of the IUGG: The State of Substance in the Earth's Interior (V. A. Magnitsky, Convener) and the Final Report, Upper Mantle Project (V. V. Beloussov, Chairman). Most of the papers presented at these two symposia are published in special issues of Physics of the Earth and Planetary Interiors (volume 5, pp. 267-343) and Tectonophysics (volume 13, pp.

Stresses due to phase changes in subduction zones and an empirical equation of state for the mantle

“…Equations of state for rocks have commonly been determined by compressional experiments or seismic velocity determinations on single crystals and monomineralic samples (Clark 1966;Chung 1971Chung ,1972Anderson 1972;Ahrens 1975)…”