A new study reveals that deep, slow-moving rock flows within the Earth’s interior have played a fundamental role in shaping the planet’s strongest large-scale gravitational anomaly beneath the Antarctic continent. This anomaly manifests as a pronounced deficit in gravitational pull over Antarctica compared to other regions of Earth—an effect not caused by topographic depression but rather by an extensive mass deficiency in the subsurface.

To investigate the origin and evolution of this unique gravitational feature, researchers reconstructed the internal dynamics of Earth over nearly 70 million years. Their approach integrates high-resolution seismic tomography—derived from earthquake wave propagation to image the deep interior—with geophysical models simulating the extremely slow deformation and flow of rocks in the mantle. This combination enables a detailed reconstruction of mantle convection processes beneath Antarctica as an animated timeline across geological time scales.

The findings reveal a critical transition between approximately 50 and 30 million years ago. During an early phase, the gravitational anomaly was primarily driven by the continuous sinking of cold, dense crustal material into the deeper mantle along the Pacific and South Atlantic margins surrounding the Antarctic continent. This process contributed to mass loss in the region.

Subsequently, a new dynamic emerged: a vast, multi-thousand-kilometer-wide column of hot, buoyant rock began rising from deep within the mantle beneath the Ross Sea region. The sustained ascent of this less dense material significantly altered the regional mass distribution under the continent.

The synergistic interaction between the descending cold rocks at the continental margins and the ascending hot plume below the central Antarctic region intensified the mass deficit. This dual mechanism led to a progressive stabilization and intensification of the gravitational anomaly, resulting in its current extreme magnitude—making it the largest known continental-scale gravitational anomaly on Earth.

Remarkably, this period of profound internal change coincides with a well-documented shift in Earth’s rotational axis, known as polar wander, which occurred around 50 million years ago. The study thus establishes a direct link between deep mantle circulation, large-scale variations in surface gravity, and subtle yet measurable changes in the planet’s orientation in space.

By tracing the development of the Antarctic gravitational anomaly over tens of millions of years, this research provides an integrated understanding of the interplay among internal geodynamic processes, Earth’s gravitational field, and its rotational behavior. It demonstrates how slow, imperceptible movements within the deep Earth—occurring over geological timescales—can generate measurable surface signals and even influence the planet’s orientation in space.

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Filed under: Anomaly,Geology,Science News - @ February 4, 2026 7:15 am