It is found in the depths of Indian Ocean and named as the gravity hole or Indian Ocean geoid low, an anomaly on earth where gravity is said to be weaker, and levels of sea dip by more than 328 feet (100 m) underwater. Discovered in 1948, it puzzled scientists all those years until newly created computer models could explain it via tectonic shifts and magma movement well into the gaping bowels of our planet.
140 million years ago: the generation of this ‘gravity hole’, the Indian Ocean
The gravity hole can be traced back to 140 million years ago when it was a part of the now-non-existent Tethys Ocean between the supercontinents of Laurasia and Gondwana. When the Indian plate traveled northwards and collided with the Eurasian plate, the crust of Tethys was subducted into the mantle of the Earth.
This pushed the dense material of the “African blob” aside, where low-density magma plumes rose and weakened gravity, subsequently creating the geoid low. In 2023, researchers used 19 computer simulations, confirming that magma plumes and mantle structure were critical to the creation of this anomaly with six of them simulating the geoid low.
The Indian Ocean Geoid Low is an examination of the gravity anomalies of the earth
Earth’s appearance never gives one the impression that it is a smooth sphericity but instead reminds of an “ellipsoid”- bulging at the equator. Earth also has discrepancies that affect the gravity pull. “The Earth is basically a lumpy potato,” geophysicist Attreyee Ghosh explains, one of the lead researchers studying the gravity hole.
These irregularities are compliments of planet dynamics such as tectonic movement, mantle convection, and old geological processes. The geoid describes how unevenly gravity is distributed across the Earth. It expresses how water would naturally have settled by gravity alone.
The Indian Ocean geoid low is suggesting being deeper-than-average for a considerable geoidal area (1.2 million square miles), constituting the largest gravitational anomaly ever captured. Its round-shaped depression on the southern tip of India exhibits the relationship between deep mantle processes and surface phenomena.
Such study not only resolves this Indian Ocean gravity hole, but it also creates a context of comprehension of other gravitational anomalies scattered over the globe. Such processes probably operate in other low geoids, and consequently, geological maps will contribute towards a better understanding of the complex forces acted upon Earth over millions of years.
The mystery of the Indian Ocean gravity hole: A chapter in the evolving history of Earth
Up to 20 million years ago existed the Indian Ocean gravity hole in that time, while then to-date nothing by which its future can be predicted at the level of hundred million years. It would carry that tag “wrap” when these tectonic plate movements continue with their action of being as such.
But at this moment, it still lives on, being just a very incomplete chapter in Earth’s geological history and what has shaped the hitherto growing and shaping Earth. Science has not come to the end of its journey in solving this anomaly.
For instance, the simulations do not consider the mantle plume that fuels the volcanic activity at Réunion Island, the reason for the development of the Deccan Traps 65 million years ago. This highlights the difficulty of constructing models for processes that have occurred over millions of years and depend on ill-complete information about Earth’s history.
Also, there is a known deviation between the modeled geoid and the actual geoid due to the present available data, especially in regions of interest like the Pacific and Africa. These disagreements between models and data highlight that models need to be further refined, and that data acquisition should continue using tools such as seismic imaging.
Out of these deep voids forms the gravity hole of the Indian Ocean over and above all the other processes that once used to be there but now are not visible, like evaporating oceans, molten magmas in ascending plumes, and much more. There is still much to learn about this research geophysical marvel; it keeps deepening understanding and adds a lot more surprise about an ever-changing planet with deep mysteries still hidden beneath the surface.
