Why is the Earth’s gravity weakest in an area of the Indian Ocean?

Why is the Earth’s gravity weakest in an area of the Indian Ocean?

Scientists find why there is giant ‘hole' in Indian Ocean, where Earth’s gravity is at weakest

Introduction

The Earth's gravity is not the same everywhere on the planet. It varies depending on the shape, rotation and mass distribution of the Earth. One of the most prominent anomalies in the Earth's gravity field is the Indian Ocean geoid low (IOGL), which is a region where the sea level is about 106 meters lower than the global average. This means that the gravity is weaker in this area than anywhere else on Earth. But what causes this giant 'hole' in the Indian Ocean? Scientists have been puzzled by this question for decades, until now.

New study

A new study by Debanjan Pal and Attreyee Ghosh from the Centre for Earth Sciences at the Indian Institute of Science in Bengaluru, India, has proposed a plausible explanation for the origin of the IOGL. They used computer simulations to reconstruct the plate tectonic movements and mantle convection over the last 140 million years. They found that the IOGL is related to the sinking of an ancient ocean bed and the rising of hot mantle plumes.

Ancient ocean bed

The ancient ocean bed that Pal and Ghosh refer to is the Tethys Ocean, which existed between the continents of Gondwana and Laurasia before they broke apart and formed the modern continents. As the continents drifted, some parts of the Tethys Ocean floor subducted under Africa, creating a deep trench. These subducted slabs of oceanic crust sank into the mantle, where they disturbed the large low-velocity province (LLVP), which is a region of hot and dense material at the base of the mantle under Africa.

Mantle plumes

As a result of this disturbance, some parts of the LLVP became less dense and rose as plumes of hot mantle material. These plumes reached the surface under the Indian Ocean, creating volcanic islands such as Reunion and Mauritius. The plumes also reduced the mass and density of the mantle under the IOGL, creating a low-gravity anomaly.

Summary

The IOGL is a region where the Earth's gravity is at its weakest, due to a combination of factors:

- The Earth is not a perfect sphere, but bulges at the equator and flattens at the poles.
- The mass distribution of the Earth's crust, mantle and core varies across different regions.
- The IOGL is located above a zone of low-density mantle plumes that originated from a deep layer under Africa.
- The mantle plumes were triggered by the sinking of an ancient ocean bed that subducted under Africa millions of years ago.

Source

(2) There's a gravity 'hole' in the Indian Ocean and now we may know why. https://www.newscientist.com/article/2379320-theres-a-gravity-hole-in-the-indian-ocean-and-now-we-may-know-why/.
(3) Origin of mysterious giant ‘gravity hole’ in Indian Ocean unravelled .... https://www.independent.co.uk/news/science/indian-ocean-gravity-hole-origin-b2367149.html.


FAQ's

Where is the lowest gravity on Earth India?

One such point of low gravity is found just south of the Indian peninsula, called the Indian Ocean Geoid Low (IOGL). The geoid low spans a vast extent south of the Indian subcontinent, and is dominated by a significant low of minus 106 metres, or roughly 348 feet, south of Sri Lanka.

Where is the weakest gravity on Earth?

Somewhere roughly in the middle of the Indian Ocean is the deepest dent in Earth's gravitational field – the place where Earth's gravitational pull is the weakest.

What is a gravity hole?

(Grades K-4) series. A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying. Because no light can get out, people can't see black holes.

Which part of the Earth has a stronger gravity?

However, gravity isn't the same everywhere on Earth. Gravity is slightly stronger over places with more mass underground than over places with less mass.

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