Deep Roots of the Antarctic Gravity Anomaly Traced Back to the Age of Dinosaurs

A groundbreaking geophysical study released in 2026 has unveiled the ancient origins of the most significant gravitational anomaly on our planet. Hidden beneath the vast ice sheets of Antarctica, this unique region of low gravity has been traced back approximately 70 million years, reaching into the late Cretaceous period when dinosaurs still roamed the Earth. This phenomenon, which represents the weakest gravitational pull found anywhere on the globe, is the direct result of profound density variations within the deep-seated rock structures of the Earth's interior.

To uncover these subterranean secrets, an international consortium of scientists, including experts from the Paris Institute of Earth Physics, utilized sophisticated techniques to construct a comprehensive three-dimensional model of the planet's internal architecture. This process, which researchers liken to performing a high-resolution computer tomography (CT) scan of the entire Earth, allowed for unprecedented visualization. Key figures in this endeavor, such as Professor Alessandro Forte from the University of Florida and Petar Glisovic, synthesized global seismic data with advanced physical modeling to reconstruct the complex dynamics of the mantle, spanning from the modern era back to the dawn of the Cenozoic era roughly 66 million years ago.

The formation of this specific gravitational depression, scientifically referred to as the Antarctic geoid anomaly, was driven by a dual-action mechanism involving two powerful and opposing mantle processes. On one side of the continent, massive volumes of cold and exceptionally dense rock were found to be sinking deep into the mantle along the Pacific and South Atlantic margins. Simultaneously, a contrasting upward movement was occurring beneath the Ross Sea, where a colossal plume of significantly hotter and less dense material was rising from the depths of the ocean floor, creating a complex interplay of forces.

According to the study's sophisticated modeling, the most intense phase of this anomaly's development occurred between 50 and 30 million years ago. This specific geological window is particularly noteworthy because it aligns perfectly with a major shift in the Earth's rotational axis. This temporal coincidence suggests a profound and intrinsic relationship between the convection currents churning within the Earth's mantle, the resulting configuration of the global gravitational field, and the overall orientation of the planet within space.

These gravitational variations, which are fundamentally caused by the uneven distribution of mass and density beneath the surface, have a tangible and direct impact on the topography of the world's oceans. In regions where the gravitational pull is weaker, such as the area identified under Antarctica, water masses naturally migrate toward zones with stronger attraction, leading to a localized drop in sea level relative to the Earth's center. Understanding these deep-seated geophysical processes is vital, as Professor Forte emphasizes that these insights are crucial for determining the factors that influence the growth, movement, and long-term stability of major continental ice sheets.

Historically, the Indian Ocean Geoid Low, first identified in 1948, was considered the most significant depression in geodetic models. However, the new research introduces a hydrostatic approach that filters out the Earth's equatorial bulge caused by its rotation. When this centrifugal flattening is removed from the calculations, the true pole of the minimum gravitational potential shifts decisively toward Antarctica, specifically centered over the Ross Sea. This discovery indicates that the Antarctic anomaly provides a much clearer and more accurate reflection of the planet's internal dynamics, stripped of the distorting effects of planetary rotation.

The findings, which have been documented in the prestigious journal Scientific Reports, have confirmed the high degree of accuracy of the underlying geophysical models. The reconstructed gravity maps produced by the team showed a near-perfect correlation with the benchmark data collected by modern satellite missions. Moving forward, the scientific team continues to investigate the causal links between the evolution of this gravitational well and historical changes in polar ice cover, seeking to answer fundamental questions about the interconnectedness of the Earth's deep interior and its complex climate systems.