Earth’s Magnetic Shield Has a Growing Hole in It. Science Just Found the Cause.

Two continent-sized blobs of superheated rock buried 2,900 km below Africa and the Pacific have been steering our magnetic field for 265 million years.

Image by Novy Bafouka

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In 2009, at Fairbanks International Airport in Alaska, something strange happened. Overnight, the runways changed their names. Runway 1L-19R became 2L-20R.

No construction.

No renovation.

The concrete was the same. The only thing that had changed was that the numbers painted on the ground no longer matched reality. North had moved. The runway was no longer pointing in the right direction.

At Geneva Airport in Switzerland, 100 sign panels were replaced, and 150 kilograms of paint were applied to correct the numbers on the runway. In Austin, in Reno, in Denver — airports across the United States and around the world have been forced, one by one, to rename their runways. Because the north that your compass, your aircraft, and your phone use to tell you where to go is no longer where it used to be. And nobody knows exactly why.

Two Norths

To understand what’s happening, you first need to know that there are two norths. The first is the geographic North Pole — the fixed point at the top of the globe where Earth’s rotation axis meets the surface. It doesn’t move. The second is the magnetic north pole: the point a compass needle actually points toward, where the lines of Earth’s magnetic field plunge vertically into the ground. And that one moves.

It has always moved. When British explorer James Clark Ross located it for the first time in 1831, it was in the Canadian Arctic, roughly 1,600 kilometers south of the geographic pole. For more than a century and a half, it drifted slowly between 5 and 15 kilometers per year somewhere in northern Canada. Nothing alarming.

Then, in the 1990s, something changed. The magnetic pole accelerated without warning, without explanation. Its speed multiplied roughly sixfold, reaching about 55 kilometers per year in the early 2000s. Its direction changed, too. Instead of wandering through the Canadian Arctic, it set a direct course toward Siberia. It crossed out of Canadian waters in 2000 and crossed the international date line in 2017. According to NOAA’s World Magnetic Model 2025, the pole currently sits at approximately 85.8°N and 139.3°E — closer to Russia than to Canada. Magnetic north is leaving the West.

It has since decelerated to around 35 kilometers per year — the sharpest slowdown ever measured. But 35 kilometers per year is still three to four times faster than anything recorded across the previous four centuries.

The World Built on a Moving Point

The runway numbering is just the visible surface of a much deeper problem. By FAA rules, runway numbers reflect the magnetic compass bearing to the nearest 10 degrees. When the pole moves far enough, the numbers no longer round to the right value, and airports are required to repaint. The FAA, NOAA, and the British Geological Survey jointly maintain the World Magnetic Model — the reference standard used by airlines, military navies, submarines, GPS systems, oil drilling companies, and every single navigation application on every smartphone on the planet.

Photo by Ravi Palwe on Unsplash

When you follow a route by car, your phone continuously corrects for the difference between geographic north and magnetic north. Geophysicists call this gap magnetic declination. It varies by location and changes over time. If the correction is out of date, drift accumulates. On a journey of 8,500 kilometers from South Africa to the United Kingdom, using the old model instead of the current one will put you 150 kilometers off course — the difference between landing in London and landing somewhere around Calais.

The WMM is normally updated every five years. In 2019, for the first time in its history, scientists had to issue an emergency update outside the scheduled cycle — the pole was moving so fast that the predictions were becoming dangerously imprecise. This year, NOAA published a high-definition version of the model with ten times the resolution of the standard version, with real-time corrections for aurora-related disturbances in polar regions. The message is simple:

The tools of yesterday are no longer sufficient to track what is happening beneath our feet.

The Animals That Felt It First

Humans aren’t the only ones with a problem. In 1882, a French naturalist named Camille Viguier published a hypothesis that was ignored for more than a century. He claimed that birds and other animals could navigate by detecting Earth’s magnetic field through their inner ears. He was right.

Science has since confirmed that dozens of species possess a magnetic sense. Migratory birds have proteins called cryptochromes in their retinas — proteins whose quantum states respond to magnetic fields. Their eyes literally show them which direction is north. Some species also carry crystals of magnetite in their upper beaks, a naturally magnetic mineral that functions as a biological compass. In November 2025, a study published in Science confirmed Viguier’s original intuition: pigeons detect magnetic fields through specialized cells in their inner ears, using the same electromagnetic induction principle that powers wireless phone charging. His hypothesis had been dismissed and forgotten. It took 143 years to vindicate him.

Sea turtles imprint the magnetic signature of their birth beach into their brains as hatchlings. Years later, after traveling thousands of kilometers through the open ocean, they find their way back by following the magnetic signature they memorized as newborns. Salmon inherit a genetic magnetic map of the mouth of their birth river. Humpback whales — which hold the record for the longest migration of any mammal — carry magnetite in their skulls and travel 9,500 kilometers in a nearly straight line year after year, following the same route with astonishing precision. When researchers experimentally alter the magnetic field around migratory birds, the birds become disoriented, choose incorrect routes, or display unusual searching behaviors. When small magnets are attached to toads, they lose their ability to locate their breeding sites.

The entire navigational machinery of the living world rests on a magnetic field that was assumed to be stable. That field is currently changing faster than it has at any point since systematic measurement began.

What’s Actually Driving It

The answer lies 2,900 kilometers beneath our feet, and that’s where the story takes an unexpected turn.

Earth’s magnetic field is not produced by a giant buried magnet. It is generated in the outer core — a layer of molten iron and nickel at several thousand degrees, roughly 2,200 kilometers thick. This liquid metal is electrically conductive and in constant motion. The convection currents, combined with Earth’s rotation, produce electrical currents that generate the magnetic field. Scientists call this mechanism the geodynamo. The principle is the same as a hydroelectric turbine: a conductive fluid in motion producing electricity and magnetism. Except here, the turbine is 7,000 kilometers in diameter, has been running for 4 billion years, and nobody controls the thermostat.

Photo by BoliviaInteligente on Unsplash

What we observe at the surface — the displacement of the pole — is the shadow of what’s happening in that furnace. The ESA’s Swarm mission satellites, in orbit since 2013, have mapped these deep dynamics with unprecedented precision. What they revealed is that there is no single magnetic north pole in the simple sense of the term. There are two extensive regions of intense magnetic flux in the northern hemisphere: one lobe beneath Canada and one beneath Siberia. These two lobes have been engaged in a permanent tug of war. Since the 1970s, the Canadian lobe has been weakening while the Siberian one has been strengthening. The most recent Swarm data show that the Canadian strong-field region has shrunk by an area comparable to the size of India, while the Siberian region has grown by an area comparable to Greenland. The magnetic pole isn’t drifting randomly — it is being pulled toward the dominant force, drawn toward Siberia by a growing imbalance.

In February 2026, a study published in Nature Geoscience by the University of Liverpool added a crucial piece to the puzzle. Combining paleomagnetic data — measurements of the field trapped in ancient rocks — with geodynamo simulations run on supercomputers, researchers identified two colossal rock structures, each the size of a continent, buried at the base of Earth’s mantle beneath Africa and beneath the Pacific. These superheated masses of solid rock are not part of the liquid outer core, but they alter the temperature contrasts at the core-mantle boundary. Beneath these tropical zones, liquid iron stagnates instead of circulating normally, and this disruption has been influencing the geodynamo for at least 265 million years.

Professor Andy Biggin, lead author and professor of geomagnetism at Liverpool, summarized it directly. Some parts of the magnetic field have remained remarkably stable for hundreds of millions of years, while others have changed spectacularly. It is these two giant structures — the Blobs — that have been orchestrating the entire arrangement.

The Shield with a Hole in It

The movement of the pole is one symptom. There’s a second phenomenon that receives less attention but may be more consequential.

Above the South Atlantic, between South America and Africa, there is a zone where Earth’s magnetic shield is abnormally weak. It’s called the South Atlantic Anomaly. This is where the Van Allen radiation belt — which traps high-energy solar particles — descends closest to Earth’s surface, at just 200 kilometers altitude. In this zone, satellites absorb elevated radiation doses. The Hubble Space Telescope shuts down some of its detectors during each pass. The International Space Station requires reinforced shielding. Astronauts report seeing phantom shooting stars in their visual field, caused by cosmic rays passing directly through their retinas.

Using 11 years of magnetic field data from the Swarm constellation, scientists have determined that the South Atlantic Anomaly has expanded by an area nearly half the size of continental Europe since 2014. Since 2020, a region southwest of Africa has been weakening even faster. “The South Atlantic Anomaly is not just a single block,” says lead author Chris Finlay, Professor of Geomagnetism at the Technical University of Denmark. “It’s changing differently towards Africa than it is near South America. There’s something special happening in this region.”

The explanation connects directly to the Blobs. Beneath the anomaly, the magnetic field lines don’t behave as they should in the southern hemisphere. Instead of emerging from the core, they reverse and plunge back into it. These reverse flux patches are migrating westward over Africa, and their movement is what is widening and deepening the weak zone.

Is a Reversal Coming?

This is the question that comes to everyone’s mind eventually, and it deserves a direct answer.

Earth’s magnetic field has reversed hundreds of times in the planet’s history. Over the past 170 million years, scientists have counted roughly 540 inversions. The most recent complete reversal — the Brunhes-Matuyama event — occurred approximately 780,000 years ago. The average interval between reversals is roughly 250,000 years. By that arithmetic, we are statistically overdue by more than 500,000 years. And overall field intensity has declined by about 10% since systematic measurements began in 1840.

A study published in early 2026 by researchers at the University of Utah analyzed marine sediments 40 million years old and found something troubling: some past reversals didn’t take the typical 10,000 years but lasted as long as 70,000 years. During these extended transition periods, Earth’s magnetic shield was drastically weakened, more cosmic radiation reached the surface, atmospheric chemistry changed, and biological evolution was likely affected. The researchers noted that during a reversal, both high-altitude and surface environments are exposed to increased cosmic radiation, with potential consequences for organisms that navigate magnetically and for genetic mutation rates.

Is a reversal currently underway? Probably not. At least not in any near-term human sense.

The WMM 2025 shows no precursor signs of imminent pole reversal. A separate study from Lund University reconstructed the magnetic field across 9,000 years and showed that configurations similar to today’s have occurred before without ever triggering a reversal. The South Atlantic Anomaly itself could resolve within the next 300 years. And volcanic rocks from St. Helena Island, located at the center of the anomaly, show the zone has been unstable for at least 11 million years without ever causing a flip.

But here is what scientists openly admit:

They cannot predict what will happen. The behavior of Earth’s core is, in its own words, chaotic and unpredictable. We cannot observe the flow of liquid iron 2,900 kilometers down. We can only infer its movements from what we measure above the surface. It is a little like trying to understand the currents of an ocean by watching only the waves that arrive on shore.

And that may be the most vertiginous part of this entire story. We have built an entire world — from GPS satellites to whale migrations to numbers painted on airport concrete — on the premise that north is a fixed point.

It isn’t.

[embed]They Eliminated Friction. And Then Explained Why You Exist. Two papers. Same month. The same fundamental question.medium.com

It never was. It was just moving slowly enough that nobody noticed. Today it moves at 35 kilometers per year, pulled by continent-sized blobs of rock that have been shaping Earth’s magnetism for a quarter of a billion years, above a hole in our magnetic shield that is quietly growing, while sea turtles navigate with a GPS that is 100 million years old and is being asked to cope with a field that is reconfiguring itself beneath them.

North is not a place. It is a promise the Earth makes, and lately it has been renegotiating the terms.

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(Originally published at The Nov Science)