Is Earths Inner Core Solid or Not?

Earth's core, which measures about 4,300 miles across, is comprised mostly of iron and some nickel, along with a few other elements. The outer core remains liquid, enveloping the solid inner core.

The conventional explanation of the formation of the solid inner core involves slow cooling and crystallization. Because the melting temperature increases with pressure, the core will solidify from the center outwards. But this effect also means that as pressure increases because of accretion, ...

We can further constrain our compositional model by using inner-core compositional models and experimental metal–silicate partitioning data. Recent studies have proposed that the inner core is a Fe–Ni–Si alloy containing between 1 and 2% silicon (8, 30).

The properties of the inner core (1C) of the Earth are widely assumed to be consistent with those of pure, solid iron in the hexagonal close-packed (ε) phase. This hypothesis is re-examined here using a density model of the Earth's core generated from extrapolated, static high-pressure data ...

Solids 61, 461–465 (2000). ... J. M. Brown, R. G. McQueen, Phase transitions, grüneisen parameter, and elasticity for shocked iron between 77 GPa and 400 GPa. J. Geophys. Res. 91, 7485–7494 (1986). ... L. Vočadlo, D. P. Dobson, I. G. Wood, Ab initio calculations of the elasticity of hcp-Fe as a function of temperature at inner-core pressure. Earth Planet.

Seismological studies indicate that the inner core of Earth is anisotropic for compressional waves (P waves), and has low shear wave (S wave) velocity, and high seismic attenuation. Using an effective medium theory for composite materials, we show that the presence of a volume fraction of 3 to 10% liquid in the form of oblate spheroidal inclusions aligned in the equatorial plane between iron crystals is sufficient to explain the aforementioned seismic phenomena.

John Vidale, Dean’s Professor of Earth Sciences at the USC Dornsife College of Letters, Arts and Sciences and principal investigator of the study, said the researchers “didn’t set out to define the physical nature of the inner core.” · “What we ended up discovering is evidence that the near surface of Earth’s inner core undergoes structural change,” Vidale said.

In the 1980s, however, analyses ... not be totally smooth (3). Another aspect of Halley’s now debunked theory was that the inner core could rotate separately from the rest of the Earth....

We observe this effect in the atmosphere where supercooled water droplets persist in the liquid state until snow forms around dust particles or ice flash-freezes on aircraft wings. These examples also illustrate the importance of heterogeneous nucleation, where a pre-existing solid (e.g. an aircraft wing) reduces the energy barrier and allows rapid freezing. Supercooling is the missing ingredient from current models of inner core formation.