Scientists have detected a strange continent-scale anomaly in the eastern Atlantic Ocean that can only be explained by a massive redistribution of mass deep beneath our feet, near the lower boundary of the Earth’s mantle. The anomaly, which occurred in 2007, was discovered in data collected by gravity-monitoring satellites and is linked to a phase change of material in the mantle.
Researchers led by geophysicist Charlotte Gaugne Gouranton analyzed data from the Gravity Recovery and Climate Experiment (GRACE) mission, which orbited Earth from 2002 to 2017. The anomaly was detected as a subtle but vast dipole pattern with stronger gravity in one band and weaker just next to it, spanning about 7,000 kilometers over the eastern Atlantic.
The team ruled out surface processes such as shifting water as the cause of the anomaly, as it would require an impractically large amount of moving water. Instead, they proposed that the phase change of bridgmanite, a mineral abundant in the Earth’s mantle, could have caused the mass redistribution.
Bridgmanite can undergo a phase transition under high pressures and temperatures found at the core-mantle boundary, changing its lattice configuration and density. This transformation would rapidly redistribute mass in the region, producing dramatic shifts in the gravity field above. The team also found a link between this anomaly and a geomagnetic jerk recorded by other satellites.
While the research has yet to be confirmed, it raises important questions about the dynamics of Earth’s interior. Future studies will investigate how common these mass redistributions are and how they fit into the broader landscape of Earth’s interior processes.
Source: https://www.sciencealert.com/vast-anomaly-in-earths-gravity-field-signals-shifts-deep-beneath-the-surface