A colossal and perplexing phenomenon referred to as a “gravity hole” has long intrigued geologists beneath the Indian Ocean. Contrary to what the term implies, this is not an actual hole. Instead, it represents a massive anomaly in the Earth’s crust characterised by significantly lower gravity than the surrounding area. Known scientifically as the Indian Ocean geoid low (IOGL), this depression spans over two million square miles and lies approximately 600 miles beneath the Earth’s crust.
Dutch geophysicist Felix Andries Vening Meinesz first discovered it during a ship-based gravity study in 1948. The origin of this “gravity hole” is still being researched by scientists. Recently, scientists from Bengaluru’s Indian Institute of Science put out a potential explanation for this puzzling gravitational anomaly.
Previous research neglected the IOGL’s genesis in favour of focusing on its current status. This new study, however, goes into its historical history to comprehend how prehistoric influences have influenced its present state.
Scientists used a variety of computer models that included data about the region’s changes during the previous 140 million years as a result of the movement of Earth’s tectonic plates to study the gravity drop. By taking into account a number of variables, they also reproduced the convection of molten material within the mantle.
The findings indicate that the IOGL is a result of a distinct mantle structure, combined with another mantle anomaly known as the African blob or large low-shear velocity province (LLSVP). Certain portions of tectonic plates are believed to have descended into the mantle beneath Africa, triggering plumes under the Indian Ocean.
Attreyee Ghosh, one of the study’s authors, explained to Scientific American, “What we’re seeing is that hot, low-density material coming from this LLSVP underneath Africa is sitting underneath the Indian Ocean and creating this geoid low.”
The research team suggests that the geoid assumed its present form around 20 million years ago and will likely persist as long as mantle material continues to flow.
According to geologists, the structure of the mantle beneath the Indian Ocean presumably came from the seafloor of the long-gone Tethys Ocean. The Laurasian and Gondwanan supercontinents were split by this ancient ocean about 200 million years ago. Africa and India were formerly a part of Gondwana, but some 120 million years ago, India moved north into the Tethys Ocean, eventually giving rise to the Indian Ocean.
The authors admit that the IOGL may be caused by several underlying causes. However, this “Gravity Hole” serves as a reminder that the Earth is home to many mysteries that still need to be explored and understood.