In the middle of the Indian Ocean there is a huge gravitational hole that has puzzled scientists for decades. The million square kilometer anomaly is not a physical hole, but a region of the ocean where Earth’s gravity is below average.

Scientists studying the “hole” have long believed that something underneath is causing a strange effect. But a new study suggests that researchers should look around the gravitational hole, not below, to unravel the mystery of its formation.

The study says plumes of molten rock rising from the remains of the ancient ocean floor may be the cause.

The gravitational force changes very little on the earth’s surface.

Many of these variations are easily explained. But scientists have had trouble explaining the gravitational hole in the Indian Ocean known as the Indian Ocean Geoid Trench.

“The gravitational difference is not large. You certainly wouldn’t have noticed if you were standing at the very center of the anomaly,” said Bernhart Steinberger, a geodynamic researcher at the German Geosciences GFZ Research Center.

However, it is quite significant that the ocean level in the area of ​​2.8 million square kilometers is about 90 meters lower than the surrounding oceans.

“I think people often assume that there must be something with low density underneath causing it. But this article actually has a different theory,” said Steinberger.

To understand what caused the hole, geophysicist Attriye Ghosh and postdoctoral researcher Debanjan Pal of the Indian Institute of Science in Bangalore asked a computer to simulate what might have happened.

They created 19 scenarios for how tectonic plates might have moved around the hole over the past 140 million years.

published work, Geophysical Research Lettersfound that only a few scenarios could explain the gravitational hole, and that none of these models had low gravity caused by what was directly below it.

Instead, they found the hole was likely composed of low-density magma plumes.

“This is something you might think about before, you just don’t think about it because you tend to think there must be something underneath,” said Steinberger, who was not involved in the research.

According to the research, the most likely explanation for the gravity hole dates back to the breakup of the supercontinent Gondwana, which gave rise to Africa, Australia and India about 120 million years ago.

When India broke away from Africa and struck the European plate, the ocean that used to be there called Tethys split in two and was crushed between continental plates. Some small pieces of the plate are still present in the Mediterranean, but most of this plate is slowly melting deeper into the Earth around East Africa.

“This pulls the surface down, causing a large region of reduced gravity,” Steinberger said. Said.

As the dense mantle melts, it forms low-density magma plumes. This and other surrounding masses, such as the Tibetan Plateau, create a relative gravitational height and amplify the effect, Steinberger said.

Himangshu Paul, a scientist at the National Geophysical Research Institute in India, said: New Scientistthat future studies of the ocean should confirm whether these plumes exist in real life, not just in computers.