Lab Experiments Point to Layered Inner Core Explaining Seismic Anomalies

Measurements on iron–silicon–carbon alloys under core-like conditions reveal crystal alignment that matches the 3–4% wave‑speed difference along Earth’s axis.

Overview

An international team from the University of Münster, DESY’s PETRA III, the University of Lille and ESRF reports results that account for long‑standing inner‑core observations.
Diamond‑anvil cell tests with a graphite heater compressed Fe–Si–C alloys to roughly a million times atmospheric pressure and above 820 °C, replicating deep‑Earth conditions.
X‑ray methods directly captured a lattice‑preferred orientation forming during compression, a microstructural feature that makes wave speeds direction‑dependent.
Material properties derived from the experiments were fed into theoretical models indicating composition changes with depth, with iron content increasing inward, producing anisotropy consistent with seismology.
The study, published in Nature Communications and funded by the DFG and ERC under the LECOR program, supports an onion‑like, multi‑layer structure for the solid inner core.