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Scientists just found a massive 7,000 kilometer-long gravitational anomaly off the coast of Africa in data from a NASA satellite. The anomaly occurred from 2006 to 2008 and has now disappeared. What caused it? Let's have a look.
Huge Gravity Anomaly Near Africa | 6:49
Sabine Hossenfelder | 1.75M subscribers | 717,927 views | November 25, 2025

YouTube transcript reformatted at textformatter.ai
I find it both fascinating and creepy that we live on the thin solid surface of a planet that's still hot and liquid in the core. And we don't know exactly what's going on inside of it. There's all this hot stuff slushing around and God knows what it's doing. Worse, a new paper now found that something very strange has been going on just off the coast of Africa, where a major gravitational anomaly has occurred. Let's have a look.

We're used to geological events happening over millions of years, but this gravitational anomaly amazingly happened within just a couple of years, from 2006 to 2008 just west off the coast of Africa. And it's huge; in the North-South direction, it stretches about 7,000 kilometres -- that's roughly the distance from London to Chicago. The researchers found this anomaly in data collected by the GRACE satellites.

The GRACE mission was a joint project between NASA and the German Aerospace Centre. It was a pair of satellites that took data from 2002 to 2017. They were flying one behind the other a few hundred kilometres apart, and they were exchanging very exact signals in the microwave range. With this, they could measure the distance between them to a stunning precision -- micrometres over hundreds of kilometres.

When the pull of gravity would change from one region to the next, the front satellite would notice that first and move a little relative to the rear one. From this, they could infer changes in Earth's gravitational field very precisely. NASA is working on a follow-up mission called GRACE-C that may or may not launch in 2028.

The authors of the new paper now looked at this data from the GRACE satellites and found that there was this rapid change in the gravitational field near Africa. It's not simply that gravity got stronger or weaker, but that it changed faster from one region to the next. And then, two years later, that stopped. It's rare for geophysicists to find something that changes faster than your smartphone model.

Stranger still, this gravitational anomaly happens to coincide with an anomaly in the magnetic field that was observed in the same region at the same time and that had been reported earlier. A coincidence? Possibly. But the combined evidence suggests that something was going on -- something literally very deep.

So what is going on there? The scientists first considered that since this gravity anomaly was measured in a part of the ocean, maybe the ocean currents changed. This could move a lot of water around and thereby change the local gravitational pull. But that didn't fit the shape or size of the anomaly.

The authors of the new paper then came up with an explanation that fits the data much better, and that's quite something. They suggest that deep in the Earth's mantle, roughly 3,000 kilometres deep, a big area of rock began to move upwards. This is called an upwelling. But then what happens is that as it moved up, the pressure dropped, and that caused a phase transition in the major mineral.

This mineral is called bridgmanite, and it's a kind of perovskite. Yes, that's the same class of mineral that is also being used for solar panels. As the pressure dropped, that changed into a different configuration, and that increased the density. This, the researchers say, caused the sudden change in the gravitational pull. Then, as the stuff moved further up, it spread out, and the effect diluted until it disappeared. At least, this is what they think happened.

This isn't the first gravity anomaly on Earth, but it is one of the more mysterious. Another famous gravity anomaly is an area of unusually low gravitational pull over Hudson Bay in Canada. There is another huge gravity low in the Indian Ocean. But these have been there for as long as we have made measurements. What GRACE saw in 2007 is different -- a gravity change on a remarkably short time scale.

What about the sudden change in Earth's magnetic field? Well, it's somewhat unclear if these two things are related. By the way, if you remember, a few months ago I told you about this hole in the magnetic field of Earth over South America. New observations say that this actually got larger. And here, too, the currently most widely accepted explanation is that something is moving around in the core of our planet.

None of this is directly worrisome. But let me be honest; this kind of stuff freaks me out. Just think about the gigantic, enormous masses that are moving around under our feet. I think that this puts our little human doings into perspective.

So the good news is the Earth is stable again. The bad news is we're not sure why it wasn't. But what really worries me is that we can measure Earth's gravity to micrometre precision, but no one's yet invented a package that actually opens where it says "open here."

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Great stuff, thanks for posting!

It cracks me up how we humans, with our pitifully short lifetimes, make the default assumption that everything has always been the way it is now, and should always be that way into the future. That's so dumb.

The surface temperature changes. The climate/weather changes. The ocean currents change. The continents drift around. Right under our thin-thin crust is magma -- "liquid hot magma" -- that spurts out through cracks and shoots into the air and makes island chains. The model of the earth that has a solid inner core and a soft outer core and a softer mantle is too simplified and the boundaries aren't fixed. The magnetic poles move around at timescales we can track, and there's lots of evidence that from time to time they reverse.

We live on a geomagnetic dynamo. Should we be the least bit surprised that gravity is dynamic?

Anyway, great post, thanks again!