Scientists explain the mysterious gravity hole in Indian Ocean

Scientists think that they might be able to explain ‘gravity hole’ in the Indian Ocean.

In case you’re not aware of what a ‘gravity hole’ is – and you won’t be alone – we’ll have a go at explaining what it is, without getting too bogged down in the complex science.

So, there’s an area deep underneath the waters of the ocean that has been baffling scientists for a while.

It’s not exactly a small area, either.

At around three million square kilometres, it’s not an insignificant chunk of the earth to be confused about.

Anyway, it’s a gravity hole, which is where the pull of gravity is low, which causes the seafloor to sink down.

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Now, two intrepid scientists from India’s Institute of Science – Debanjan Pal and Attreyee Ghosh – have posited a potential solution.

That solution could lurk 1,000 kilometres – around 621 miles – beneath the Earth’s crust, where the scientists found there is a cold and dense area that is the remains of an old ocean that was plunged into a ‘slab graveyard’ beneath Africa around 30 million years ago, churning up a load of molten rock in the process.

Got all of that? No? Well, we’ll power on regardless.

The two scientists looked at how tectonic plates have moved over the Earth’s surface over 140 million years, running simulations and then comparing them to the underwater dent that is this gravity hole.

They discovered that the simulations that produced the Indian Ocean geoid low as it appears now all shared similar characteristics, including plumes of hot and low-density magma coming up beneath the low point.

ESA - GOCE High Level Processing Facility

The scientists reckon these plumes of magma – as well as the mantle structure – causes the gravity hole.

Still struggling? Well, let’s give them a crack at explaining it, shall we?

"In short, our results suggest that to match the [shape and amplitude of the] observed geoid low, plumes need to be buoyant enough to come up to mid-mantle depths," said the pair.

The first plume such as this one appeared about 20 million years ago, just at the south of the Indian Ocean geoid low, about 10 million years after the Tethys Sea sank down into the Earth’s lower mantle.

The plumes moving around beneath the lithosphere heading slowly up towards the Indian peninsula saw the geoid low intensify.

ESA

It’s tough stuff to get into, but it is interesting once you attempt to get your head around it.

There’s a lot more research to be done to find out what the definitive truth is, as not all members of the scientific community are convinced by this argument.

But, that’s the great thing about science.

There’s always a bit more to do.