indian ocean geoid low gravity iogl
© International Centre of Global Earth Models (ICGEM)Also known as a geoid, the gravity hole isn't a physical hole, but a region of the ocean where gravity is lower than average. The Indian Ocean geoid low (IOGL) is the deepest geoid on Earth
Indian Ocean has a 'gravity hole' where sea levels are 300ft lower - experts think they know why 7-8 minutes

Scientists have known about the existence of a 'gravity hole' in Indian Ocean for decades but have long been left puzzled as to why it exists.

Known officially as the 'Indian Ocean Geoid Low', it isn't a conventional physical hole, but rather a region of the ocean where gravity is lower than average. This dip in gravity means the water level is around 340 feet lower than the surrounding area - like a groove in a 'bumpy potato'.

Now, a team of researchers in India claim the gravity hole was formed by plumes of low-density magma that rose up from Earth's mantle.

These plumes were generated by the remains of a sunken tectonic plate called Tethys, lost when India became part of Asia 50 million years ago.

earth mantle crust inner outer core geology
© MailOnlineEarth's mantle is a layer of silicate rock between the crust and the outer core. Pictured are the layers of our planet
Mantle plumes - upwellings of abnormally hot rock within the Earth's mantle - are generally thought to caused by gravitational anomalies around the Earth.

The new study was conducted using computer simulations by two geophysicists at the Indian Institute of Science in the city of Bengaluru.

'Using these simulations we could see this geoid low being non-existent at some point and then taking shape at about 20 million years ago,' study author Attreyee Ghosh told MailOnline.

'Such kind of studies would help us address many of the Earth's still unresolved features in the future.'

Earth is often depicted as a perfectly round sphere in illustrations and physical globes, but experts think it's more like a 'bumpy potato' in terms of its shape.
gravity anomaly indian ocean geoid
© European Space Agency'Geoid anomalies' are generated by uneven mass distribution within the deep Earth. One such point of low gravity is found just south of the Indian peninsula, called the Indian Ocean Geoid Low (IOGL), spanning a vast extent south of the Indian subcontinent
Our planet's uneven surface is due to areas of non-uniform gravity resulting from the unequal distribution of matter in its interior. Adding to the surface deformations is the movement of tectonic plates that have created mountains and valleys on the Earth's surface.

No more is this illustrated than by the Indian Ocean Geoid Low, which can be found around 700 miles south of the Indian peninsula.
Felix Andries Vening Meinesz
© Woodwalter/wikimediaThe 'Indian Ocean Geoid Low' was discovered in 1948 by Dutch geophysicist Felix Andries Vening Meinesz (pictured)
It was discovered in 1948 by Dutch geophysicist Felix Andries Vening Meinesz during a ship-based gravity survey, when he found the sea level in the region was significantly lower than the global average, indicating a gravitational anomaly.

While we have sent missions to probe the outer reaches of our solar system, the deepest boreholes on Earth go down to only a few miles, so looking for answers within our planet is somewhat of a challenge.

To address this, the experts used computer software to track how Earth's tectonic plates may have moved around the hole in the past 140 million years. Violent interactions between the tectonic plates may hold clues about why this gravitational anomaly exists today, they figured.

It's well known that Earth's lithosphere - its rocky, outermost shell - is formed of around 15 tectonic plates that are constantly moving and grinding past each other.