Earth's core has baffled researchers for decades, and it still contains many secrets.
Recent studies show this hot furnace buried deep under our feet is weirder than we think.
The inner core may be spinning, and scientists think it is encased by an ancient ocean floor.
The Earth's mysterious core is crucial to every part of life on our planet.
This furnace of molten metal, which lies about 1,800 miles beneath our feet, keeps our atmosphere intact and protects us from being bombarded by solar radiation.
But scientists still don't really understand exactly how it works. We can't go down there, for obvious reasons, so researchers have to rely on shockwaves traveling through Earth to give us clues into what's really going on in our planet's heart.
Recent studies have revealed a series of surprising discoveries about the core, and now scientists say they are beginning to unravel its secrets.
There's a huge dent in Earth's magnetic field over South America, and the core may be to blame
Though the ground may seem still to us, there's a lot happening inside our planet. Below the Earth's cold, brittle crust and its mantle of molten rock sits the core.
Inside the core, temperatures are so hot that metal oozes like a liquid that churns furiously.
That's crucially important for all life on Earth: as this metal swirls, it creates strong magnetic fields that sprout out of the Earth's poles.
These magnetic fields, in turn, act as a shield for our planet, keeping our atmosphere in place and deflecting the worst of solar radiation that constantly floods Earth.
That's why scientists are so puzzled by a big chunk of the Earth's magnetic field that has been getting weaker over the past 50 years.
Nestled above the middle of the South American continent, the South Atlantic Anomaly is an area where slightly more solar radiation is thought to pierce through the Earth's protection.
People on Earth are still safe from this radiation. But satellites and spacecraft could suffer more damage as they sail through this zone, Insider reported in 2020.
The anomaly has been getting bigger over the past 50 years and it has also started to split into two blobs, baffling scientists.
"The challenge now is to understand the processes in Earth's core driving these changes," Jürgen Matzka, from the German Research Center for Geosciences, said in a statement from the European Space Agency accompanying the finding in May 2020.
Giant mountains five times higher than Everest could be keeping the core warm
The mantle is a lot colder than the core, and it follows that the outer edge of the core should get gradually cooler to meet the temperature of the layer above it.
But it doesn't — the temperature shoots up at the boundary between the mantle and the core.
This has prompted experts to think an unknown layer or phenomenon probably exists at the core-mantle boundary to keep our planet's heart toasty. A study published in April provides a potential solution.
Scientists studying how shockwaves from earthquakes bounce off the core have suggested that it may be wrapped in bits of ancient ocean floors that have been "recycled" over millions of years as they were squeezed back into the Earth by continents smashing into each other.
Ancient ocean floors would be the perfect candidates to explain the stark change in temperature: they are very dense so can easily sink to the bottom of the mantle, and also quite heat resistant, Samantha Hansen, study lead author and geological sciences professor of the University of Alabama, previously told Insider.
Looking at the seismic data, scientists have found that this layer, which would be acting like a blanket for the core, could feature peaks five times the size of Everest, a study coauthor said in a press release.
The Earth's inner core may be spinning and might sometimes flip backward
The core itself is not uniform. At our planet's heart, the pressure becomes so intense that the metal can no longer liquefy. Instead, it behaves like a huge ball of solid metal — this is called the inner core.
Because it floats around in a pool of molten metal, our inner core doesn't necessarily rotate at the same speed as the planet. In fact, a recent study found that the inner core may have recently stopped spinning and could start flipping the other way.
The theory is that the magnetic field that pulls at the Earth's inner core competes with a strong gravitational field from the mantle, a huge lump of rock that sits right above the core.
Every few decades or so, one force may win over the other, Insider's Morgan McFall-Johnsen and Chris Panella previously reported.
That's nothing to panic about. Indeed, it looks like the same thing happened around 1971, the study found. And the world didn't stop spinning then.
Even though this phenomenon is "probably benign", scientists will want to learn more about it, John Vidale, a geophysicist at the University of Southern California, told The Washington Post in January.
"We don't want to have things we don't understand deep in the Earth," he said, per The Post.
The core may be growing lopsided
The core is always growing. Every year, more of the inner core's iron crystallizes, adding about a single millimeter to its radius.
We've known this for quite some time. But a 2021 study has raised eyebrows among scientists.
The study found the eastern part of the sphere, which is located under Indonesia's Banda Sea, seems to be getting about 60% more iron crystals than the other side.
In short, our Earth's inner core is growing sideways, per the study.
Still, that doesn't mean the inner core is growing into a football. Scientists think that though the crystals appear on one side of the inner core, they are redistributed to the other side so that it can keep its spherical shape, Insider previously reported.
This new information probably tells us just as much about the mantle above the core: it's likely that this side of the mantle is a little cooler than its Western counterpart, scientists said.
The question then, study co-author and UC Berkeley seismologist Daniel Frost told LiveScience at the time, is "does this change the strength of the magnetic field?"
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