Researchers already found that towards the mid-zone of the Indian Ocean, there is a region where the mass density of the ocean surface is significantly low. Consequently, the earth's gravitational pull is lowest in that part of the ocean which scientists describe as a hypothetical hole in the middle of the ocean floor. But there was no explanation for such anomalistic geological phenomena until now.
A convincing justification has been offered by two eminent geologists, Debanjan Pal and Attreyee Ghosh, from the Centre for Earth Sciences at the Indian Institute of Science in Bengaluru, in the southern Indian state of Karnataka. They think that it originated from an old ocean floor that submerged as a result of plate tectonic events.
They suggest that it might have been brought on by plumes of molten rock rising from deep beneath Africa at the edges of the sinking remnants of an ancient ocean bed by reconstructing the last 140 million years of tectonic plate movements and the underlying mantle that went along with the rearrangement of Earth's crust. The shape of Earth is not perfect. If that were true, gravity would have been constant throughout its whole surface. The blue globe actually bulges out around the equator and is flatter around the North and South Poles than a true spherical would be.
As a result of the bulk of the Earth's crust, mantle, and core underneath them, various locations pull in different directions with respect to gravity. The Indian Ocean Geoid Low (IOGL) is the name given to the geoid's prominent dip in the Indian Ocean. The most noticeable gravitational anomaly on the globe is this one. It has a surface area of more than three million square kilometers and is positioned roughly 1,200 km southwest of India's southernmost point.
It follows that the dip isn't noticeable at the surface since the ocean always seems to be rather flat. The water level of the Indian Ocean above the hole is shockingly 106 meters lower than the world average as a result of the low gravitational attraction there combined with the stronger gravitational pull from the surroundings, according to a new study.
The IOGL was found in 1948 by Dutch geophysicist Felix Andries Vening Meinesz during a ship-based gravity survey, said the study's main author Debanjan Pal. Since then, multiple ship missions have been made, and the hole has been measured by satellites, but until recently, no one knew why it was there. They contend that it is existing as a result of a different mantle structure and a nearby disturbance under Africa known as a large low shear velocity province (LLSVP), sometimes referred to as the "African blob."
According to Ghosh, "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." According to Pal, "Tethyan slabs" deep in the mantle are likely what generated the African blob, which is primarily responsible for the IOGL. Geologists believe that these ancient seabed fragments are from the Tethys Ocean, which existed more than 200 million years ago between the supercontinents Laurasia and Gondwana.
Both Africa and India were formerly a part of Gondwana, but around 120 million years ago, as present-day India progressively migrated north into the Tethys Ocean, it left the Indian Ocean in its wake. "Plumes [of molten rock] arise when subducted slabs belonging to the old Tethys Ocean sink inside the mantle and reach the core-mantle boundary," he claimed. We demonstrate that, in addition to these plumes, the mantle structures nearby also contribute to the formation of this low.