Earth's gravitational pull is not uniform; it is "lumpy," with significant variations across the globe. One of the most striking examples is in East Antarctica, where gravity is measurably weaker than anywhere else on the planet, according to recent scientific findings. This unusual "gravity hole" originated at least 70 million years ago due to slow-moving convection deep within Earth's mantle.[kottke+2]
Earth's Uneven Gravity Field
Earth's gravity varies subtly from place to place, making the planet a geophysically "lumpy" sphere rather than a perfectly smooth one. This unevenness comes from several factors. The distribution of mass within the planet is not uniform, with different densities in its constituent parts.For instance, areas with dense rock, like iron ore, have slightly stronger gravity. Regions with less mass underground, such as valleys or deep ocean trenches, show weaker gravitational forces.[quora+4]
The Earth's rotation also plays a role, causing a slight bulge at the equator. This makes gravity about 0.3% less there compared to the poles.Elevation also affects gravity. The higher the altitude, the further from Earth's center, which slightly reduces gravitational pull.Local topography, such as mountains, and underlying geological structures, like crustal thickness, contribute to these gravity anomalies.[quora+10]
Ancient Mantle Dynamics Shaped Antarctic Gravity
The significantly weaker gravity in East Antarctica, often called a "gravity hole," is a long-standing anomaly. Scientists now understand this gravitational deficit formed at least 70 million years ago. It is linked to the slow movement of rock deep within Earth's mantle.[kottke+2]
Early gravitational lows in this region were primarily a result of convection. Cold, dense mantle material had been sinking over millions of years. Then, somewhere between 50 and 30 million years ago, a slight shift occurred in Earth's rotational axis.This shift led to warmer, less-dense material, previously trapped deep in the mantle, moving upward. As colder mantle material continued to sink, the lower density beneath Antarctica reduced the region's overall mass, creating the pronounced gravity hole.[popularmechanics+1]
Petar Glišović and Alessandro M. Forte, researchers in this field, suggest that these mantle processes coincided with Antarctica freezing over about 30 million years ago. They believe the shift in mantle dynamics that triggered the gravity hole's formation could also affect sea levels and Antarctic ice sheets. Water naturally shifts toward areas with stronger gravity. In regions with weaker gravity, like East Antarctica, the ocean surface sits slightly lower than expected.[popularmechanics+1]
Satellites Monitor Earth's Changing Gravity
Scientists use advanced satellite missions to measure and track these subtle changes in Earth's gravity field. The Gravity Recovery and Climate Experiment (GRACE) and its successor, GRACE Follow-On (GRACE-FO), are joint missions by NASA and the German Aerospace Center (DLR). These twin satellites orbit Earth, about 220 kilometers (140 miles) apart, and precisely measure the distance between each other.[earthdate+2]
When the lead satellite passes over an area with stronger gravity, it speeds up slightly. This increases the distance between the two satellites. When it passes over weaker gravity, the distance decreases. Amicrowave ranging system measures these tiny changes in distance, down to a few thousandths of a millimeter, or about one-tenth the width of a human hair. Onboard accelerometers also help remove non-gravitational forces, ensuring accurate gravity measurements.[earthdate+8]
GRACE data provides global snapshots of Earth's gravity field. This helps track mass changes in polar ice, water reservoirs, and geological structures. The missions have revolutionized understanding of the Earth's water cycle, revealing groundwater depletion and significant ice loss from Greenland and Antarctica.[geodesy+5]
East Antarctica's Ice Mass Dynamics
East Antarctica, which holds about 90% of Earth's solid freshwater, was long considered a stable ice sheet. However, GRACE mission data from 2002 to 2009 showed that the East Antarctic ice sheet began losing mass, mainly in coastal regions, at an estimated rate of 57 gigatonnes per year.[grace]
More recent studies using satellite gravimetry have shown complex changes. From 2003 to 2014, Antarctica's ice sheet lost an average of 92 billion tons of ice per year. Most of this loss came from West Antarctica. During the same period, East Antarctica's ice sheet thickened, but only accumulated half the amount of ice lost from the west.[grace]
A study published in April 2025 revealed that Antarctica experienced accelerated mass loss from 2011 to 2020, at a rate of 142.06 ± 56.12 gigatonnes per year. This included intensified mass depletion in West Antarctica and the Wilkes Land-Queen Mary Land (WL-QML) region of East Antarctica. However, a significant reversal occurred between 2021 and 2023. The entire Antarctic Ice Sheet gained mass at a rate of 107.79 ± 74.90 gigatonnes per year, driven by anomalous precipitation. Four key glaciers in the WL-QML region of East Antarctica, including Totten, Moscow University, Denman, and Vincennes Bay, shifted from accelerated mass loss to significant mass gain during this 2021-2023 period.[princeton+2]
These findings highlight the dynamic nature of Earth's gravity field and its direct connection to processes both deep within the planet and on its surface. Understanding these intricate gravitational variations is crucial for monitoring climate change impacts, such as ice sheet stability and global sea levels.[eurekalert]
