Indian Ocean gravity hole: The dent in Earth's gravitational field created by the death of an ancient ocean

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2024-11-23 17:00:10

The Indian Ocean "gravity hole" is a region where Earth's mass is reduced, leading to weak gravitational pull, lower-than-average sea levels and a puzzle scientists have only just begun to solve.

The Indian Ocean "gravity hole" is the site of the deepest dent in Earth's gravitational field. It's a circular ocean region with a gravitational pull that's so weak, sea levels are 348 feet (106 meters) lower there than elsewhere on Earth. Discovered in 1948, the origins of this giant gravity hole — or geoid low, as it is technically called — remained a mystery until recently.

The hole spans 1.2 million square miles (3.1 million square kilometers) and sits 746 miles (1,200 km) southwest of India. Various theories have tried to explain its existence since geophysicists first detected its trace, but the answer only came in 2023 with a study published in the journal Geophysical Research Letters. Researchers used 19 computer models to simulate the motion of Earth's mantle and tectonic plates over the past 140 million years, and then teased out the scenarios giving rise to a geoid low similar to the real-life one.

The study indicated that the Indian Ocean gravity hole formed after the death of an ancient ocean called Tethys, which existed between the supercontinents Laurasia and Gondwana. Tethys sat on a chunk of Earth's crust that slipped beneath the Eurasian plate during the breakup of Gondwana 180 million years ago. As this happened, shattered fragments of the crust sank deep into the mantle.