The enigmatic colossal 'gravitational anomaly' in the Indian Ocean, and the reasons behind its creation

A phenomenon identified as a 'gravity hole' exists in the Indian Ocean, where the Earth's gravitational force is weaker, causing a depression in sea level exceeding 328 feet. Geologists have been perplexed by this anomaly for some time, but recent research suggests a plausible explanation: magma plumes from deep within the Earth, similar to those responsible for volcanic activity.

 Using supercomputers, researchers simulated the region's evolution over 140 million years, leading to the hypothesis outlined in a recent study published in the journal Geophysical Research Letters. This hypothesis focuses on a vanished ancient ocean as a key component.

The Earth's uneven shape and varying densities play a significant role in shaping its surface and gravitational field. According to Attreyee Ghosh, a geophysicist and associate professor at the Centre for Earth Sciences of the Indian Institute of Science, differences in density across the globe directly impact its geoid, which is the theoretical surface where water would evenly distribute under gravity's influence.

The 'gravity hole' in the Indian Ocean, also known as the Indian Ocean geoid low, is the largest gravitational anomaly in this area. It creates a circular depression, originating from the southern tip of India and covering roughly 1.2 million square miles. This anomaly was initially observed by Dutch geophysicist Felix Andries Vening Meinesz in 1948 during a gravity survey, and its cause has yet to be fully understood.

In an effort to shed light on this puzzle, Ghosh and her team utilized computer simulations covering 140 million years, monitoring the movements of tectonic plates and magma within the Earth's mantle. In six of the nineteen simulations conducted, a geoid low similar to the one observed in the Indian Ocean appeared. The crucial element in these models was the existence of magma plumes, thought to be the driving force behind the creation of the 'gravity hole,' stemming from the vanishing of an ancient ocean as India's landmass shifted and eventually collided with Asia millions of years ago.

The fate of the geoid low remains uncertain, having formed around 20 million years ago. Its longevity or disappearance hinges on the movements of Earth's mass anomalies. Huw Davies, a professor at Cardiff University, views the research as intriguing and anticipates it will spur additional inquiry. However, Dr. Alessandro Forte, a geology professor at the University of Florida, raises reservations regarding the study's modeling approach and the disparities between predicted and observed geoids.

Ghosh acknowledges limitations in the simulations but remains confident in the overall explanation for the 'gravity hole' phenomenon.