Open AccessAn Equation of State for the Core of the Earth
Author(s) -
Knopoff Leon,
MacDonald Gordon J. F.
Publication year - 1960
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1960.tb00066.x
Subject(s) - inner core , outer core , core (optical fiber) , compressibility , core–mantle boundary , earth (classical element) , geology , mantle (geology) , equation of state , shock wave , geophysics , boundary value problem , physics , thermodynamics , mineralogy , mechanics , quantum mechanics , optics , mathematical physics
Summary Recent shock wave measurements upon the compressibility of iron and eight other metals, at pressures up to five megabars, permit an investigation of the equation of state of the Earth's core. The density of iron at T = 0 at 1.4 megabars (core‐mantle boundary pressure) is 11.8. The density at the core boundary is estimated to be between 9–1 and 10.1, depending upon the particular Earth model. The temperature correction is small. The discrepancy can only be resolved by stating that the core is not pure iron, but rather that it contains significant amounts of alloying elements of lower atomic number than iron. The seismic velocity in pure iron at core pressures is also significantly different from the velocity in the core and also indicates the existence of lighter components within the core. A material of mean atomic number 23 in the core is consistent with the shock wave velocity and density measurements and with seismic observations.