A Solenoid

Melting Earth's core in the laboratory by using laser-heating technique in the diamond-anvil cell. Probing extremes.Melting Earth's core in the laboratory by using laser-heating technique in the diamond-anvil cell. The laser-heated diamond-anvil cell is used to simulate the conditions at Earth's core. Melting of core materials can be detected by in situ synchrotron x-ray diffraction and textural examination of the quenched samples. Yingwei Fei Science 2013;340:442-443 Published by AAAS

Low-Pressure Iron Phase Diagram

Body-centered cubic (α-iron and δ-iron) Face-centered cubic (γ-iron) Hexagonal close-packed (ε-iron)

Fig. 2 Pressure (PKCl)–temperature conditions at which XRD patterns have been collected.Different symbols correspond to different Fe phases and textures. Pressure (PKCl)–temperature conditions at which XRD patterns have been collected.Different symbols correspond to different Fe phases and textures. The continuous black lines correspond to Eqs. 1, 2, and 3. Data are in table S1. S. Anzellini et al. Science 2013;340:464-466 Published by AAAS

Fig. 3 Phase stability domains for Fe obtained in the literature and in this study.The stability field for ε-Fe is based on the current study data and data from (19). Phase stability domains for Fe obtained in the literature and in this study.The stability field for ε-Fe is based on the current study data and data from (19). S. Anzellini et al. Science 2013;340:464-466 Published by AAAS

Fig. 4 Temperature profile (geotherm) in the lower mantle and the outer core.Dark blue curve, solidus of pyrolite (this study); light green curves, liquidus and solidus of pyrolite (7). Temperature profile (geotherm) in the lower mantle and the outer core.Dark blue curve, solidus of pyrolite (this study); light green curves, liquidus and solidus of pyrolite (7). Melting (liquidus) temperatures of pure Fe (3), Fe-O-S alloy (26), and FeH (17) are shown by black, pink, and blue lines, respectively. The dashed curves represent extrapolations of experimental data. Ryuichi Nomura et al. Science 2014;343:522-525 Published by AAAS

The density–pressure relationships for Fe92.5O2.2S5.3 and Fe90O8S2. HJ Huang et al. Nature 479, 513-516 (2011) doi:10.1038/nature10621

The bulk sound velocity as a function of density for Fe92. 5O2. 2S5 The bulk sound velocity as a function of density for Fe92.5O2.2S5.3 and Fe90O8S2. HJ Huang et al. Nature 479, 513-516 (2011) doi:10.1038/nature10621

Density versus pressure and bulk sound velocity for Fe92. 5O2. 2S5 Density versus pressure and bulk sound velocity for Fe92.5O2.2S5.3, Fe90O8S2, Fe90O0.5S9.5 and pure iron along the adiabatic geotherm, compared with the PREM model. HJ Huang et al. Nature 479, 513-516 (2011) doi:10.1038/nature10621

Inner Core Anisotropy: different in the Eastern and Western Hemispheres

Source, ray path and receiver geometry. J Wookey & G Helffrich Nature 454, 873-876 (2008) doi:10.1038/nature07131

PKJKP Data J Wookey & G Helffrich Nature 454, 873-876 (2008) doi:10.1038/nature07131

Possible models for Inner Core Anisotropy a, Outer-core convection in Taylor columns leads to larger equatorial heat-flux, promoting freezing at the ICB in these regions. This is dynamically unstable, leading to deformation symmetrically about the rotation axis. b, Crystal alignment due to dendritic solidification. As liquid iron freezes onto the ICB, dendrite structures might be formed and could persist deep into the inner core. c, Alignment due to Maxwell stresses: stresses exerted by the Earth's magnetic field (B) re-orient crystals of inner-core iron, leading to large-scale texturing. [Wookey and Helffrich, 2008]

Streamlines for the l = 1 pattern of convection in the inner core Streamlines for the l = 1 pattern of convection. The arrow defines the axis of convection. Bruce A. Buffett Geophys. J. Int. 2009;179:711-719

[M. Bergman]

A schematic representation of the translational convective mode. T Alboussière et al. Nature 466, 744-747 (2010) doi:10.1038/nature09257

Paths of the PKIKP wave (solid line) refracted inside the inner core and the PKiKP wave (dashed line) reflected at the inner-core boundary at distance 140°. (A) Paths of the PKIKP wave (solid line) refracted inside the inner core and the PKiKP wave (dashed line) reflected at the inner-core boundary at distance 140°. (B) Examples of records corresponding approximately to the same epicentral distance (140°) but to increasing distances ΔG of their turning point to point G [see (C)]. Solid circles are PKIKP waves; open circles are PKiKP waves. Travel-time differences increase with increasing ΔG values. Data are vertical components, band-pass filtered at 0.7 to 2.0 Hz. Dates and station codes are given on the right. (C) Map of the differential travel-time residuals PKiKP-PKIKP plotted at the ray turning points (Mollweide projection). Solid circles are best-quality data (8). Contours are plotted every 20° from point G (thick cross) and roughly delineate regions of equal residuals. (D) Differential travel-time residuals and (E) quality factors (in logarithmic scale) as a function of the distance of the ray turning point to point G. Solid circles are best-quality data. Marc Monnereau et al. Science 2010;328:1014-1017

Schematic cross-section illustrating the inner-core growth model. Schematic cross-section illustrating the inner-core growth model. In a superadiabatic regime, any thermal heterogeneity of harmonic degree-one shifts the center of mass of the inner core toward its colder and denser hemisphere (left). The equilibrium position at the center of mass of Earth (o) is restored by a translation of the inner core (from dashed to solid positions). This induces a topography h that is not in equilibrium with the pressure and temperature conditions within the outer core. Crystallization on the denser hemisphere (left) and melting on the opposite side act to remove the topography, but in return amplify the density heterogeneity and maintain the center of mass shifted toward the crystallizing side. It results in a permanent translation of the inner-core material inside its boundary, whose velocity V is controlled by the phase-change kinetics. The main consequences are an increase of the age (in color) from one side (blue) to the opposite (yellow), and the subsequent grain-size increase, which is compatible with the seismological hemispherical asymmetry. Marc Monnereau et al. Science 2010;328:1014-1017

Growth rate of the radius of the inner core and uniform convective velocity as functions of the inner-core radius. T Alboussière et al. Nature 466, 744-747 (2010) doi:10.1038/nature09257

Ray paths of PKP waves and example of waveform doublet used to detect temporal change of travel times through the inner core. Ray paths of PKP waves and example of waveform doublet used to detect temporal change of travel times through the inner core. (A) Ray paths of three branches of PKP waves turning in the solid inner core (DF), the bottom of the fluid outer core (BC), and the mid-outer core (AB). (B) Highly similar waveforms recorded at one station in Alaska. This waveform doublet 93 and 03 is the best recorded doublet of this study. mb, bodywave magnitude. (C) Superimposed and enlarged PKP waveforms from the box in (B), showing a misalignment of PKP(DF). The waveforms are aligned on PKP(BC) and filtered from 0.5 to 1.0 Hz. Jian Zhang et al. Science 2005;309:1357-1360 Published by AAAS

Paths within the inner core for doublet events separated by more than 4 years, all of which show a positive time shift. Paths within the inner core for doublet events separated by more than 4 years, all of which show a positive time shift. (A) Map view of DF paths projected up to the Earth's surface, including the 93 and 03 doublet, detected by 58 stations; nine additional doublets detected at the College station, Alaska; and two additional doublets detected at the Beaver Creek array. (B) Vertical cross-section a – b showing the DF ray turning radius. Open circles are paths to single stations, filled circles are paths to arrays in Alaska, and circle size indicates the measured time change d(BC – DF) for each path, normalized to a 10-year separation. ICB, inner core boundary. Jian Zhang et al. Science 2005;309:1357-1360

Difference of BC – DF times, d(BC – DF), at station COL as a function of the time separation between the two events of the doublet. Difference of BC – DF times, d(BC – DF), at station COL as a function of the time separation between the two events of the doublet. The error bar indicates the mean (solid triangle) ± SD of the data binned over a 5-year period. The measured d(BC – DF) value has been normalized by the travel time through the inner core and then multiplied by the travel time through the inner core at the average distance of 151°. The line is the linear regression of the data with zero intercept; the slope is 0.0092 s/year with standard deviation 0.0004 s/year. Jian Zhang et al. Science 2005;309:1357-1360 Published by AAAS

Inner Core Rotation: Either east or west, with respect to mantle! Tkalcic et al. [2013] find that it might do both (wobble).

Fig. 1 PKP ray paths and travel-time curves for a 1D reference model Fig. 1 PKP ray paths and travel-time curves for a 1D reference model. Differential travel times between PKP(DF) and other three branches (AB, BC and CD) of PKP waves from 130° to 180° are used in this study. Xinlei Sun , Xiaodong Song, Tomographic inversion for three-dimensional anisotropy of Earth’s inner core, Physics of the Earth and Planetary Interiors, Volume 167, Issues 1–2, 2008, 53 – 70, 2008.

Fig. 2 All differential PKP travel-time data used in this study Fig. 2 All differential PKP travel-time data used in this study. Plotted are residuals of differential CD–DF, BC–DF, and AB–DF relative to model AK135 with ellipticity correction. The data are divided according to distance range Xinlei Sun , Xiaodong Song, Tomographic inversion for three-dimensional anisotropy of Earth’s inner core, Physics of the Earth and Planetary Interiors, Volume 167, Issues 1–2, 2008, 53 – 70, 2008.

Xinlei Sun , Xiaodong Song, Tomographic inversion for three-dimensional anisotropy of Earth’s inner core, Physics of the Earth and Planetary Interiors, Volume 167, Issues 1–2, 2008, 53 – 70, 2008.

Xinlei Sun , Xiaodong Song, Tomographic inversion for three-dimensional anisotropy of Earth’s inner core, Physics of the Earth and Planetary Interiors, Volume 167, Issues 1–2, 2008, 53 – 70, 2008.