keeps deadly cosmic rays at bay and serves to
orient our navigation systems, is generated in
Earth’s outer core, more than 1,800 miles below
the crust. “You’ve got these sort of swirling hot
masses of molten iron, bubbling and moving
around,” says Phil Livermore, PhD, a profes-
sor of geomagnetism at the University of Leeds.
These molten blobs of iron generate an electrical
current, which in turn creates a magnetic field.
In regions on Earth’s outer core where magnetic
force is strongest, the magnetic field pokes out.
“That’s what we call a f lux lobe,” Livermore says.
These shifting lobes of magnetic force deter-
mine the location of the planet’s magnetic poles
through a magnetic tug of war.
Thanks to geologic samples of magnetized
rock, we know that the magnetic poles have
periodically drifted and even flipped through-
out Earth’s history. Polar reversals occur when
magnetic north and south switch places over
the course of thousands of years. (Imagine a
north-pointing compass arrow facing Antarctica.)
This happens roughly every 200,000 to 300,000
years, with some exceptions. The latest reversal
occurred around 780,000 years ago, so, techni-
cally, we’re overdue for a switch.
Magnetic north’s recent migration has been
happening faster than at any other time since it
was first measured in the 19th century. The accel-
eration began in 1990, when the magnetic north
pole went from moving on average about nine
miles each year to as many as 37 miles by 2005.
In an effort to understand why this is happen-
ing, Livermore and his team created a series of
computer models using data from ground obser-
vatories and satellites and found that between
1970 and 1999, the f low of magnetic material at
the surface of Earth’s outer core changed. These
changes were also ref lected in the strength of the
magnetic field.
Until the 1990s, the magnetic north pole was
controlled by two fairly balanced patches of mag-
netic field beneath Canada and Russia, Livermore
says. Then the patch under Canada started to
stretch out and become weaker, shifting the bal-
ance of power to the patch in Siberia. To Joseph
Meert, PhD, a professor of geology at the Uni-
versity of Florida in Gainesville, who was not
affiliated with the study, it’s as simple as playing
with magnets: “If we remove all the math and justthink about how magnets work, it is very straight-
forward.” If two magnets are pulling on an object,
and one magnet weakens, the object drifts toward
the other magnet.
The wanderings of the magnetic north
pole have significant consequences for global
navigation. Every five years, agencies in the
U.S. and U.K. produce the World’s Magnetic
Model, which lets you calculate your position
based on magnetic north’s location. Anyone who
uses a compass—from military navigators to
commercial airline pilots—relies on the model
to pinpoint their location around the globe. As
the magnetic north pole slides across the Arctic,
the model becomes less accurate, which poses a
problem for anyone requiring an ultra-precise
reading. These errors are more pronounced in
latitudes above the 55-degree parallel, including
places like parts of Scandinavia, Greenland,
Russia, Canada, and Alaska. To account for the
accelerated motion, the agencies had to release an
emergency update to the 2020 World’s Magnetic
Model a year early.
Researchers are racing to understand what
magnetic north’s movement may mean for the
magnetic field as a whole. Livermore doesn't think
a polar reversal is imminent because, while the
magnetic north pole is sliding around, the global
structure of Earth’s magnetic field has remained
relatively stable.
The greatest challenge in studying Earth’s
magnetic field, Livermore says, is making sense of
what’s happening in Earth’s outer core. “It would
be great if we could somehow invent a device to go
visit Earth’s core, to have a look at what these lobes
of molten iron are doing and see how they interact
with the magnetic field,” he says.IT WOULD BE GREAT IF WE COULD
SOMEHOW INVENT A DEVICE TO
GO VISIT THE EARTH’S CORE, TO
HAVE A LOOK AT WHAT THESE LOBES OF
MOLTEN IRON ARE DOING.
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