In 2007, something unusual happened over the eastern Atlantic Ocean. Satellites detected a sudden change in Earth’s gravity field. This anomaly, hidden from our eyes on the surface, was caused by a significant shift of mass deep beneath us.
A team led by geophysicist Charlotte Gaugne Gouranton from Paris City University studied this strange event. They believed it stemmed from a phase change of material about 3,000 kilometers down, near the mantle’s lower boundary.
This discovery came from the Gravity Recovery and Climate Experiment (GRACE), a joint mission by NASA and DLR. These satellites, which orbited from 2002 to 2017, are more sensitive to gravity changes than ground sensors. They measure slight shifts in gravity as they travel in precise formations. These shifts can hint at changes in mass, like groundwater levels or glacial melt.
Gaugne Gouranton’s team noticed a unique pattern in the data between 2006 and 2008, peaking in January 2007. They found a dipole pattern indicating mass redistribution over about 7,000 kilometers. This discovery was even more intriguing because it lined up with a sudden change in Earth’s magnetic field, known as a geomagnetic jerk.
While researchers explored surface-level causes, they concluded that these shifts were not linked to water movements. The models showed it would be impossible for surface processes to create such a large anomaly.
Once they eliminated surface processes, the focus turned to the mantle. The mineral bridgmanite, which is abundant in the mantle, can undergo a phase transition under extreme conditions. This shift significantly alters density, quickly redistributing mass below, which explains both the gravity change and the geomagnetic jerk.
Their findings suggest patterns of mass redistribution deep in the Earth’s mantle may not be rare, but how they affect Earth’s dynamics needs further exploration. This research could enhance our understanding of Earth’s interior and its changes over time.
In fact, seismic data has uncovered unusual blobs near the core that differ from surrounding material. The site’s proximity to the 2007 anomaly raises questions about a possible connection between the two.
The team’s research is published in Geophysical Research Letters. As we gather more insights into our planet’s deep processes, the mysteries of Earth’s inner workings continue to unfold.
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