Strength of iron at core pressures and evidence for a weak Earth’s inner core
The strength of iron at extreme conditions is crucial information for interpreting geophysical observations of the Earth’s core and understanding how the solid inner core deforms. However, the strength of iron, on which deformation depends, is challenging to measure and accurately predict at high pressure. Here we present shear strength measurements of iron up to pressures experienced in the Earth’s core. Hydrostatic X-ray spectroscopy and non-hydrostatic radial X-ray diffraction measurements of the deviatoric strain in hexagonally close-packed iron uniquely determine its shear strength to pressures above 200 GPa at room temperature. Applying numerical modelling of the rheologic behaviour of iron under pressure, we extrapolate our experimental results to inner-core pressures and temperatures, and find that the bulk shear strength of hexagonally close-packed iron is only ~ 1 GPa at the conditions of the Earth’s centre, 364 GPa and 5,500 K. This suggests that the inner core is rheologically weak, which supports dislocation creep as the dominant creep mechanism influencing deformation.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- NSFDOE - BASIC ENERGY SCIENCES
- OSTI ID:
- 1088565
- Journal Information:
- Nature Geoscience, Vol. 6, Issue 7; ISSN 1752-0894
- Country of Publication:
- United States
- Language:
- ENGLISH
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