Earth’s core is growing lopsidedly, a new study suggests – and it’s been doing that for at least half a billion years

Earth's core illustration
An illustration of Earth’s core.

Think of the Earth like a geological tootsie pop.

If you were to peer more than 3,000 miles below your feet into the planet’s center, you’d see a dense, solid ball of iron roughly three-quarters the size of the moon. That iron spheroid is the inner core, and it’s nestled inside the planet’s molten outer core.

The inner core is always growing: Its radius increases by a millimeter each year as pieces of molten iron in the outer core cool and solidify into iron crystals. Although temperatures in the inner core are high enough to liquify iron, the intense pressure that deep inside the planet prevents the crystals from melting – picture it like packing a hard snowball.

But according to a recent study published in the journal Nature Geoscience, the inner core is growing lopsidedly. One half of the sphere, the eastern half under Indonesia’s Banda Sea, accrues 60% more iron crystals than its western counterpart, which is located under Brazil.

“The west side looks different from the east side all the way to the center,” Daniel Frost, a seismologist at the University of California, Berkeley, who co-authored the new study, said in a release. “The only way we can explain that is by one side growing faster than the other.”

Asymmetric growth in the core

artist's illustration of iron crystal distribution earth's inner core
A graphic showing how iron crystals are distributed and move around in Earth’s inner core.

Although the Earth is more than 4 billion years old, its inner core is younger – geologists suspect it formed between half a billion and 1.5 billion years ago, when pieces of liquid iron from the outer core first started to crystallize.

Frost’s team created a computer model that tracked the inner core’s growth over the last billion years. They found that its lopsided nature likely began as soon the core formed.

Of course, if one half has been growing faster than the other for that long, the inner core’s shape should no longer be spherical. But that’s not the case. So Frost and his colleagues think that gravity may be compensating for the asymmetrical growth by pushing excess crystals from the core’s eastern side to its western side, thereby helping the core maintain a ball-like physique.

illustration of earth's core/mantle layers
An artist’s concept of Earth’s layers, including the crust, mantle, and inner and outer cores.

Frost’s team isn’t sure why iron crystals are forming unevenly in the inner core, but he said the answer likely lies in the layers above it – both the outer core and the mantle, a 1,800-mile-thick band of hot rock on which the tectonic plates float.

“Every layer in the Earth is controlled by what’s above it, and influences what’s below it,” Frost told Live Science.

If iron is crystallizing more quickly on one side of the inner core than the other, that must mean the outer core is cooling faster on that side. So the mantle on that side, in turn, must be cooling the outer core faster than the mantle on the other side.

The genesis of that cooling chain, Frost said, could be Earth’s tectonic plates. When one plate pushes up against another, one subducts, or sinks, below the other. The subducting plate cools the mantle in that area of the planet.

The core’s lopsided growth might impact Earth’s magnetic field

Magnetosphere earth magnetic field
An illustration of Earth’s magnetic field, in blue, as it protects the planet from solar radiation.

Earth’s core plays a key role in protecting the planet from dangerous solar wind and radiation. Swirling iron in the outer core generates a magnetic field that stretches all the way from there to the space surrounding our planet.

That swirl happens, in part, because of a process in which hotter, lighter material from the outer core rises into the mantle above. There, it swaps places with cooler, denser mantle material, which sinks into the core below. This is known as convection.

Convection also happens between the inner and outer core, so if various parts of the outer and inner core are cooling at different rates, that could affect how much heat gets exchanged at the boundary – which might have an impact on the swirling engine powering Earth’s protective sheath.

“The question is, does this change the strength of the magnetic field?” Frost told Live Science.

For now, his group isn’t sure, but Frost said he’s investigating the answer.

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Sharks are among a group of animals with a 6th sense that humans don’t have – they use Earth’s magnetic field to navigate

bonnetheads sharks
Bryan Keller holding a bonnethead shark.

Shark species have an uncanny ability to find their way back to the same feeding grounds every year – even areas thousands of miles away.

According to a study published Thursday, that’s because sharks have a superior navigational tool at their disposal: They can orient themselves using Earth’s magnetic field.

They’re far from the only animals to do so. Birds, whales, and many other species use the same sixth sense to plot their migrations.

Bryan Keller, a biologist at Florida State University who co-authored the new study, likens this sense to “having an ‘internal GPS.'”

“This is, in my opinion, the best explanation for how migratory sharks successfully navigate during long-distance movements,” Keller told Insider.

‘Sharks garner map-like information from the magnetic field’

Earth's Magnetic Field
An illustration of Earth’s magnetic field.

Nearly 2,000 miles below Earth’s surface, swirling iron in the planet’s outer core conducts electricity that generates a magnetic field. This field stretches all the way from the planet’s interior to the space surrounding the Earth. It’s what protects the world from deadly solar radiation.

But the direction that the electromagnetic energy flows, as well as the strength of the resulting protective sheath, depends on where on the planet’s surface you are. So animals that use the magnetic field to orient themselves do so by detecting these differences in field strength and flow. They then use that information to figure out where they are and where to go.

Scientists long suspected sharks could navigate using the field, since the animals can sense electromagnetic fields in general. But that hypothesis had been difficult to confirm until Keller’s study.

His team examined the bonnethead shark, known as Sphyrna tiburo, because the species exhibits site fidelity – meaning it returns to the same estuary habitats each season.

“This means the sharks have the capability to remember a specific location and to navigate back to it,” he said.

bonnetheads sharks
An overhead shot of bonnethead sharks in a holding tank.

The team captured 20 bonnetheads off the coast of Florida in the Gulf of Mexico, then placed the sharks in a 10-by-10-foot tank. They generated a tiny magnetic field within a 3-square-foot area of that tank. (Bonnetheads only reach 4 feet in length, which made them an ideal species to study in such a small pool, Keller said.)

The team then tweaked that localized magnetic field to mimic the electromagnetic conditions of various locations hundreds of miles away from where they’d caught the sharks. If the animals were truly relying on magnetic-field cues to navigate, the thinking went, then the bonnetheads would try to reorient themselves and start swimming in the direction they thought would lead to the Florida coast. That’s exactly what happened.

When the researchers mimicked the conditions of the magnetic field on Florida’s Gulf Coast, the animals exhibited no preference in which direction they were swimming – suggesting they assumed they were already in the right place.

“I’m not surprised that sharks garner map-like information from the magnetic field, because it makes perfect sense,” Keller said.

Many animals use the magnetic field for navigation

Even though the new study was done on bonnetheads, Keller said the findings likely apply to other shark species as well.

Great White Shark
A great white shark heads near the Neptune Islands, Australia, in June 2014.

How else could a great white, for example, migrate from South Africa to Australia – a distance of more than 12,400 miles – then return to the exact same chunk of ocean nine months later?

“En route to Australia, the animal exhibited an incredibly straight swimming trajectory,” Keller said of great whites. “Given that the magnetic field is perhaps the only constant and ubiquitous cue available to these migratory sharks, it is sensible that magnetic-based navigation is responsible for facilitating these incredible navigational successes.”

Other navigational cues do exist, including currents and tides, but Keller said the magnetic field “is likely more useful than these other aids because it remains relatively constant.”

Biologists still aren’t sure how sharks detect the field, but a 2017 study suggested that the animals’ magnetic receptors are probably located in their noses.

The ability to detect and orient using the magnetic field is fairly common in the animal kingdom overall, according to Keller. Scientists have observed that type of behavior in bacteria, algae, mud snails, lobsters, eels, stingrays, honey bees, mole rats, newts, birds, fish like tuna and salmon, dolphins, and whales.

Sea turtles, too, rely on magnetic cues when they migrate thousands of miles to lay eggs on the same beaches where they hatched.

Two wire-haired Fox Terriers.

Dogs, meanwhile, can find their way home both using their impressive sense of smell and by orienting themselves using the magnetic field, according to a June study.

“The magnetic field may provide dogs with a ‘universal’ reference frame, which is essential for long-distance navigation,” that study said.

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Earth’s north magnetic pole is on the move – here’s what will happen when our poles flip

Following is a transcript of the video.

Narrator: Did you know that Earth has two North Poles? There’s the geographic North Pole, which never changes. And there’s the magnetic North Pole, which is always on the move. And right now it’s moving faster than usual.

Over the past 150 years, the magnetic North Pole has casually wandered 685 miles across northern Canada. But right now it’s racing 25 miles a year to the northwest.

This could be a sign that we’re about to experience something humans have never seen before: a magnetic polar flip. And when this happens, it could affect much more than just your compass.

Alanna Mitchell: Right now on the surface of the planet, it looks like it’s just a bar magnet. Our compasses are just pointing to one pole at a time because there’s a dominant two-pole system.

But sometimes, Earth doesn’t always just have a single magnetic North and South Pole. Evidence suggests that, for hundreds to thousands of years at a time, our planet has had four, six, and even eight poles at a time. This is what has happened when the magnetic poles flipped in the past. And when it happens again, it won’t be good news for humans.

Now you might think, eight poles must be better than two. But the reality is that: Multiple magnetic fields would fight each other. This could weaken Earth’s protective magnetic field by up to 90% during a polar flip.

Earth’s magnetic field is what shields us from harmful space radiation which can damage cells, cause cancer, and fry electronic circuits and electrical grids. With a weaker field in place, some scientists think this could expose planes to higher levels of radiation, making flights less safe.

This could also disrupt the internal compass in many animals who use the magnetic field for navigation. Even more extreme, it could make certain places on the planet too dangerous to live. But what exactly will take place on the surface is less clear than what will undoubtedly happen in space.

Satellites and crewed space missions will need extra shielding that we’ll have to provide ourselves. Without it, intense cosmic and solar radiation will fry circuit boards and increase the risk of cancer in astronauts.

Our modern way of life could cease to exist. We know this because we’re already seeing a glimpse of this in an area called the South Atlantic Anomaly. Turns out, the direction of a portion of the magnetic field deep beneath this area has already flipped! And scientists say that’s one reason why the field has been steadily weakening since 1840.

As a result, the Hubble Space Telescope and other satellites often shut down their sensitive electronics as they pass over the area. And astronauts on the International Space Station reported seeing a higher number of bright flashes of light in their vision, thought to be caused by high-energy cosmic rays that the weaker field can’t hold back.

Since experts started measuring the Anomaly a few decades ago, it has grown in size and now covers a fifth (20.3%) of Earth’s surface, with no signs of shrinking anytime soon. This is so extreme that it could be a sign we’re on the brink of a polar flip, or we may already be in the midst of one!

But scientists remain skeptical, mainly because …

Mitchell: They don’t know. The last time the poles reversed was 780,000 years ago so it’s not like we have a record for this.

Turns out 780,000 years is over double the time Earth usually takes between flips.

Mitchell: In the past 65 million years since the last mass extinction there have been reversals roughly every 300,000 years.

So what gives? Well, scientists haven’t figured it out yet. It’s unnerving to think that our modern way of life – banking, the stock exchange, missile tracking, GPS – relies on the outcome of something we can neither predict, nor control. One study went so far as to estimate that a single, giant solar storm today could cost the US up to $41.5 billion a day in damages.

And that’s with Earth’s magnetic field at its current strength. It’s frightening to imagine the devastation a storm would bring to an Earth with a magnetic field only 10% as strong.

We may not be able to stop a polar flip, but we can at least start to take measures to minimize the damage. The first step? Figure out what’s going on with this whacky field.

On the hunt are the European Space Agency’s SWARM satellites, which are collecting the most precise data on the strength of Earth’s magnetic field. Right now, they could be our greatest hope for solving this riddle.

EDITOR’S NOTE: This video was originally published on April 9, 2018.

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