Death of an ocean 180 million years ago created a hole in the Indian Ocean

Earth's gravitational field has a dent. Known as a "gravity hole", it lies in the Indian Ocean and is the deepest dent in our planet's gravitational field. The sea levels in this circular region are 348 feet lower than any other place on Earth. This is because of a gravitational anomaly, in this case, an extremely weak gravitational pull.

Even though it was discovered in 1948, no one knew what created it. However, a study tried to understand its origin in 2023 and came up with a startling revelation. According to it, an ancient ocean called Tethys once existed between the supercontinents Laurasia and Gondwana. Its death is what led to the formation of the gravity hole in the Indian Ocean.

The study was published in the journal Geophysical Research Letters. The hole spans 3.1 million square kilometres and is located 1,200 km southwest of India.

Researchers created a simulation of the motion of Earth's mantle and tectonic plates over the past 140 million years and came up with scenarios.

Tethys went down with a chunk of Earth's crust 180 million years ago. When Gondwana broke apart, the crust slipped beneath the Eurasian plate. When this happened, shattered fragments of the crust sank deep into the mantle.

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The African blob that is taller than Mount Everest

Around 20 million years ago, these fragments displaced high-density material originating from the "African blob" after reaching the lowermost regions of the mantle.  

The blob is trapped beneath Africa and stands 100 times taller than Mount Everest. It is made up of crystallised magma. As plumes of low-density magma rose and replaced the magma, the overall mass of the region diminished and its gravity weakened.

However, the research still needs to be corroborated with earthquake data to help verify the existence of low-density plumes beneath the hole. Several similar blobs are believed to exist in Earth's magma, even in places where they shouldn't be.

Even Mars is reported to have such blobs under its surface. Understanding what is happening under the Earth's surface is also expected to help scientists learn more about the red planet.