Mystery of massive ‘gravity hole’ solved – DW – 07/05/2023

For decades, a massive and mysterious “gravity hole” deep in the Indian Ocean has left scientists paused. This is the Indian Ocean Lower Geode (IOGL), three million square kilometers off the southern tip of India, below the surface where sea level is 105m below average. Here, the effects of Earth’s gravity are much lower than average, which has not been previously explained. The hole was discovered by Dutch geophysicist Felix Andries Venning Mainz in 1948 during a gravity survey on a ship.

To understand the new discovery, it is necessary to clarify that our planet is not a uniform sphere, but a geoid with many irregularities. This also assumes that its density is different in every region of the globe, and therefore, gravity is not the same everywhere. In some places gravitational anomalies occur, such as in the depths of the Indian Ocean. It should also be noted that it is not a place where things sink, things do not fall faster, not even a visible hole.

lost sea

A new study by two scientists from the Indian Institute of Science may be a solution to the mystery. All of these studies [pasados] They analyzed the current anomaly and didn’t care how this low geode originated,” explained geologists Dipanjan Pal and Atrei Ghosh in Study published in Geophysical Research Letters.

The study suggests that IOGL is composed of slabs of the Tethys ocean, a long-lost sea that sank deep into the planet millions of years ago.

The researchers simulated 19 different scenarios to reconstruct the movement of tectonic plates and the changes that occurred in the Earth’s mantle over the past 140 million years, using various parameters, such as viscosity, mantle density, or temperature. They discovered that ancient fragments of the oceanic plate had pushed through the mantle below the African continent, causing a sharp subsidence of the mantle and altering the geology.

“Mantle blades”, magma plumes

When a cooler plate and a hotter plate collide, columns of molten rock, called “mantle plumes” that are less dense and rise above the rest of the material, are formed. And these plumes turned back towards the Indian Ocean, where they are currently located. Gravity anomaly.

However, the authors point out that there may also be other realities that underlie the existence of IOGL, as there are still many unknown aspects of our planet.

Indeed, the researchers assert that the presence of an anomaly in the Indian Ocean could indeed have an impact on the global climate, as this phenomenon could affect ocean circulation and thus the distribution of heat on Earth.

Edited by Isabella Escobedo