Breaking: Mysterious 2007 Gravity Anomaly linked to Deep Mantle Shifts
A meaningful, unexplained anomaly detected in Earth’s gravity field in 2007 is now believed to originate from deep within the planet’s mantle, rather than surface water redistribution, according to new research published in Geophysical Research Letters. The anomaly, observed in the eastern atlantic Ocean, baffled scientists due to its scale and timing, which couldn’t be reconciled with known surface processes or core fluid flows.
Researchers initially investigated the possibility that massive shifts in oceanic and groundwater volume were responsible. However, the amount of water displacement required to create the observed gravitational shift proved physically impossible.
The study points to a phase transition within bridgmanite ((Mg,Fe)SiO),the most abundant mineral in Earth’s mantle. Under extreme pressure and temperature conditions found at the core-mantle boundary, bridgmanite can shift from a perovskite crystalline structure to a post-perovskite structure. This structural change causes a significant density shift, rapidly redistributing mass and impacting the gravity field above – perhaps explaining the 2007 geomagnetic jerk.
The location of the anomaly aligns closely with one of the “strange blobs of material” previously identified near Earth’s core through seismic data, suggesting a possible connection between the two phenomena.
“By analyzing time series of GRACE-derived gravity gradients, we have identified an anomalous large-scale gravity gradient signal in the eastern Atlantic Ocean, maximum at the beginning of 2007, which cannot be fully explained by surface water sources nor core fluid flows,” the researchers write. “This leads us to suggest that at least part of this signal could reflect rapid mass redistributions deep in the mantle.”
The frequency and broader implications of thes deep mantle mass redistributions within Earth’s overall interior dynamics remain areas for future inquiry.
