According to a new study, researchers have identified a huge gravity hole, technically known as a geoid, layer beneath the Antarctic ice surrounding the Southern Ocean. This discovery offers a glimpse into Earth’s deep interior and serves as a dynamic record of slow-moving processes that have been reshaping our planet for tens of millions of years.
The term gravity hole sounds alarming, but indicates a local danger; however, it poses no physical threat to humans. Instead, this profound anomaly reveals how material is arranged within the Earth and how that distribution has evolved over geological time.
The phenomenon occurs because when Earth’s gravity is slightly weaker, as in Antarctica, the gravitationally defined surface of the ocean, called the geoid, is closer to the center of the planet. The Antarctic Geoid Low is one of those valleys, and in geodynamic models it is the deepest long-wavelength valley in the world.
Study co-author Alessandro Forte said: “What surprised me most is how coherent the long-term story seems to be. The low gravity is not random, but short-lived. In our reconstructions this persists for much of the last 70 million years, but its strengths and geometry evolve in many ways.”
Unlocking the secrets of the deep interior of the Earth
Earth has other large gravitational anomalies, but Antarctica’s gravity gap is notable for its exceptional size, long wavelength, and persistence over tens of millions of years.
Beyond Earth, the research has implications for planetary science. Long-wavelength gravitational anomalies are fingerprints of its internal dynamics: clues to how heat escapes a planet and how dense material sinks. On worlds like Mars and Venus, orbital data reveal variations in gravity that point to ancient, large-scale geological activity.
The study’s findings represent a decade of work, building on longstanding collaborations with UT Austin seismologists who have helped develop crucial imaging of the Earth’s interior.
