Deep in the Indian Ocean lies one of Earthโs most peculiar phenomena โ a vast โgravity holeโ where the planetโs gravitational pull is astonishingly weak. This strange anomaly, technically known as a geoid low, creates a dent in Earthโs gravitational field so profound that sea levels in the area are 348 feet (106 meters) lower than the global average.
Discovered in 1948, this 1.2-million-square-mile (3.1 million square kilometers) region sits about 746 miles (1,200 kilometers) southwest of India.
For decades, its origins puzzled scientists, with theories ranging from tectonic quirks to mantle mysteries. Finally, in 2023, researchers uncovered the answer using cutting-edge computer simulations.
A Journey Through Deep Time
To solve this riddle, geophysicists turned back the clock, simulating 140 million years of tectonic plate movements and mantle dynamics across 19 computer models.
The key to the gravity holeโs formation lay in an ancient ocean called Tethys, which existed between the supercontinents Laurasia and Gondwana. When Gondwana began breaking apart 180 million years ago, chunks of Tethys’ crust were forced beneath the Eurasian plate.
These fragments plunged deeper and deeper into Earthโs mantle, and around 20 million years ago, they reached the mantleโs lowermost regions. There, the sinking fragments displaced dense material tied to the so-called “African blob” โ a towering mass of crystallized magma beneath Africa that is 100 times taller than Mount Everest. In response, lighter magma from surrounding regions rose to fill the void, reducing the areaโs overall mass and weakening its gravitational pull.
The Blob Connection
Far from being an isolated curiosity, the Indian Ocean gravity hole hints at a fascinating underground world. Earthโs mantle is riddled with mysterious โblobsโ of magma โ some dense and others surprisingly buoyant. The African blobโs role in this story has come to light, but there are still lingering questions.
Scientists aim to confirm their models with earthquake data, which could reveal more about the low-density plumes beneath the gravity hole.
And Earth isnโt the only planet with such mysteries. Mars, too, harbors its share of underground blobs, adding to the growing realization that planetary interiors are far stranger and more complex than once imagined.
The Indian Ocean gravity hole isnโt just a dent in Earthโs gravitational field โ itโs a portal to understanding the dynamic, hidden forces that shape our planet and others in the cosmos.
