🍄 Earth Shift

From potential polar reversals and precarious axis activity to inner mountains and ancient ocean floors, Earth’s chaotic core brings unpredictability to our planet’s protective magnetosphere.

Oct 11, 2024

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October 13 is International Day for Disaster Risk Reduction (IDDRR), designated by the UN as an international day that encourages every citizen and government to take part in building more disaster-resilient communities and nations. From extreme hurricanes to severe geomagnetic storms, Mother Earth is giving us a wakeup call. We need a concerted international action to reduce the risk of our new world of extremes.

Hello, we’re Alice and we are always in a state of wander. Earth is having a wobble—flipping (it’s axis) out even—but geophysicists and geologists embark on a journey to get to the core of it. Sitting comfortably? Then we’ll begin. “Earth, our rocky, watery oasis in the cosmos is the ideal place for life to flourish for a number of reasons,” reports Space. “We sit at just the right distance from our home star for liquid water to exist on the planet's surface.” The gravitational pull of other large planets helps protect us from apocalyptic collisions with wandering meteorites. And the planet's magnetic field encircles Earth with a protective barrier that shields us from charged particles hurtling through space.’

Earth’s immense magnetic field is called the magnetosphere. It protects us from cosmic rays and solar wind, a stream of ionized gases from the sun. Without it, solar wind would singe Earth's atmosphere, turning sci-fi thrills into a less thrilling reality. “Our magnetosphere plays the role of gatekeeper,” explains NASA. “Repelling these forms of energy that are harmful to life, trapping most of it safely away from Earth’s surface.”

What the flip!

Paleomagnetic records tell us Earth’s magnetic poles have reversed 183 times in the last 83 million years, according to NASA, and at least several hundred times in the past 160 million years. The time intervals between reversals have fluctuated widely, but average about 300,000 years, with the last one taking place about 780,000 years ago.

“You might imagine the magnetic field is a timeless, constant aspect of life on Earth, and to some extent you would be right,” explain geophysicists John Tarduno and Vincent Hare of University of Rochester, for The Conversation. But Earth’s magnetic field actually does change. Every so often—on the order of several hundred thousand years or so—the magnetic field has flipped. North has pointed south, and vice versa.

North Pole wandering

Talk about a flip-flop … “Recently, there have been questions and discussion about ‘geomagnetic excursions:’ shorter-lived but significant changes in the magnetic field’s intensity that last from a few centuries to a few tens of thousands of years,” reports NASA. During the last major excursion, called the Laschamps event, radiocarbon evidence shows that about 41,500 years ago, the magnetic field weakened significantly and the poles reversed, only to flip back again about 500 years later.

“Even though it was short, the North Pole did wander across North America, right out towards New York, actually, and then back again across to Oregon,” Alan Cooper, an evolutionary biologist with Blue Sky Genetics and the South Australian Museum tells NPR. He explains that it then zoomed down through the Pacific really fast to Antarctica and hung out there for about 400 years and then shot back up through the Indian Ocean to the North Pole again.

Geologists know this because lava flows and sediments created back then have bits of iron pointing in strange directions. “Lava flows in France contain bits of iron that are basically pointed the wrong way,” explains NPR. “Volcanic activity during the flip produced this distinctive iron signature as the molten lava cooled and locked the iron into place. Iron molecules embedded in sediments around the world also captured a record of this magnetic wobble, which unfolded over about a thousand years.”

Pole reversal—again

Imagine oceans of molten iron swirling deep inside the planet around the outer core – they are what generate Earth’s magnetic field. That sloshing sets up a giant bar magnet through Earth — though not a real concrete magnet, of course, reports Live Science. “This giant magnet sits at an angle of about 11 degrees from the axis around which Earth spins, according to Windows of the Universe. These poles are not in the same place as our geographic North and South poles.” This iron constantly migrates. Blobs of that iron get flipped in the opposite direction from iron atoms around them; scientists say they become "reverse-aligned." When there are enough reverse-aligned iron atoms, that giant bar magnet flips, and magnetic north becomes magnetic south.

“Fluctuations in the magnetic field caused by the movement of metallic material in the outer core have brought about full reversals of the magnetic field's polarity in Earth's past,” confirms Space. And it’s going to happen again. We just don’t know when. “This bar magnet is no Olympic gymnast,” continues Live Science. “The flipping isn't a quick turn but rather a gradual one, and can take between 1,000 and 10,000 years.”

Not feeling the force

Studies of ancient geomagnetic fields recorded in rocks have shown that polarity reversals of Earth's magnetic field are unpredictable—mainly because of the behavior of the mechanisms that are responsible for it. “The flow of the metallic fluid (mostly molten iron) in the outer core of the Earth is chaotic and turbulent,” geophysicist Leonardo Sagnotti tells Space. But we do get some clues. “Polarity reversals occur during periods of low geomagnetic field intensity, during which the intensity of the dipolar component drastically decreases, and the structure of the field is unstable."

“When the field flips it also tends to become very weak,” continue Tarduno and Hare for The Conversation. “What currently has geophysicists like us abuzz is the realization that the strength of Earth's magnetic field has been decreasing for the last 160 years at an alarming rate.” This collapse is centered in a huge expanse of the Southern Hemisphere, extending from Zimbabwe to Chile, known as the South Atlantic Anomaly. “The magnetic field strength is so weak there that it's a hazard for satellites that orbit above the region—the field no longer protects them from radiation, which interferes with satellite electronics. This field continues to grow weaker. Potentially portending even more dramatic events, including a global reversal of the magnetic poles,” writes Tarduno and Hare. Such a major shift would affect our navigation systems, as well as the transmission of electricity. And yes, the Northern Lights.

In terms of human civilization, “it is not the shifting of the magnetic poles that is directly concerning, but the resulting period of reduced geomagnetic field intensity,” sums up Space. Society is growing increasingly reliant on technology, and the effects of a reduced magnetic field intensity should be seriously considered by governments and international organizations.

If a tree falls in a forest…

Can it help future-humans twig what went on in it’s past? Yes, according to an Australian research team investigating ancient Giant Kauri trees from New Zealand. Evolutionary biologist Alan Cooper says when these trees die they fall into bogs. “The low oxygen conditions in the bogs can quite often preserve them spectacularly,” he tells NPR. Publishing in the journal Science, Cooper and colleagues say they analyzed well-preserved trees that were alive when the magnetic field last flipped out 42,000 years ago.

During these changes, the field got weak, which left Earth unprotected from cosmic rays coming in from outer space. “When those rays hit the atmosphere they created a certain kind of carbon, which got taken up by the trees and put down as wood,” reports NPR.That let the researchers see exactly when levels rose and peaked and then fell again. One tree in particular had a 1,700-year record. Its calendar-like rings let it create a precise timeline of the magnetic field changes that according to Cooper match up with other monumental events, like the ice over North America suddenly starting to grow really fast, large mammals dying off in Australia and disappearance of the Neanderthals.

Let’s do the Earth warp dance…

Earth, the third rock from the sun … sure, but not just a rock. Inside it sits a solid metallic ball, slightly smaller than the moon, and at 9,800-ish degrees Fahrenheit, nearly as hot as the surface of the Sun. This core — that scientists call Earth’s “beating heart” — boasts seas of heavy metal, olive-green crystals and mountains the size of Everest.

Yes, 1,800 miles beneath us is a blazing-hot ball of metal. No one has ever seen it, heard it or touched it, but still its reputation got out.

“Earth’s core is wilder than you can imagine,” writes Mashable Science Editor Mark Kaufman. The core is about the size of Pluto. And seismologists say that Earth’s core holds all the ancient secrets. “Think of it as a time capsule — a fossilized record that takes us back into the deep past and tells us more about the planet’s evolution,” writes ANU Reporter, the online magazine for The Australian National University [ANU]. Not only can the inner core enlighten us about events that happened on Earth hundreds of millions to billions of years ago, it’s an “engine room” integral to sustaining the planet’s magnetic field, which is what makes all life possible.

“The ultimate goal is to connect all of Earth’s onion layers to the way our planet formed, which in turn will help explain how it became the life-friendly world it is today,” reports NBC. David J. Stevenson, a planetary scientist at the California Institute of Technology, traces the story back to a moment 4.5 billion years ago when Earth was struck by a planetary body the size of Mars. The debris kicked up by that collision is thought to have made the moon, but it also remade our planet.

An axis to find

And perhaps, we humans are remaking our planet again… Just when you thought we had done enough, humans have managed to shift Earth’s axis by pumping so much groundwater. A study published in the journal Geophysical Research Letters last year, estimates that between 1993 and 2010, the pumping of groundwater and the resulting sea-level rise caused the poles to drift by about 2.6 feet.

Anything from ocean currents, to shifting molten rock in the mantle, to the melting of glaciers caused by climate change can lead to a shift in the distribution of mass across the globe and coax the axis to drift, reports Smithsonian Magazine. “Water stored in artificial reservoirs and seasonal changes in atmospheric winds can play a role as well, write the study authors.”

Pumping groundwater was the second-largest contributor to the axis drifting, behind the melting Greenland ice sheet. The researchers used a computer model to look at the effects of different factors on the shift of the poles. When they didn’t include groundwater removal in their model, their predictions did not match the level of shift that scientists have observed. But when they took into account the massive amount of pumped water — which totaled more than two trillion tons between 1993 and 2010 —their model fit the real-world observations.

“Every mass moving around on the surface of the Earth can change the rotation axis,” Ki-Weon Seo, a co-author of the study and a geophysicist at Seoul National University, told Nature. “The very way the planet wobbles is impacted by our activities,” Surendra Adhikari, a geophysicist at NASA’s Jet Propulsion Laboratory who did not contribute to the research, told Science. “It is, in a way, mind boggling.”

A negative leap second

Leap years, we all know, are the extra day we’re awarded every four years for good behaviour. But now it looks like we’ll have time deducted. “Leap seconds” are traditionally added to make up for irregularities in the Earth’s spin, but for the first time ever, a second could be taken away. However you spin it, this doesn’t sound good.

“Global warming is managing to actually measurably affect the rotation of the entire Earth,” says Duncan Agnew, a geophysicist at the University of California at San Diego. “Things are happening that have not happened before.” His study published in Nature, shows how increased melting of ice in Greenland and Antarctica is changing Earth’s rotation.

‘The planet is not about to jerk to a halt, nor speed up so rapidly that everyone gets flung into space,’ reports The Washington Post. ‘But timekeeping is an exact science in a highly technological society, which is why global authorities more than half a century ago felt compelled by the slight changes in Earth’s rotation to invent the concept of the “leap second.”’

Since 1972, a leap second has been added 27 times, the last of which was in 2016. Climate change is now making these calculations even more complicated: In just a few years it may be necessary to insert a “negative leap second” into the calendar to get the planet’s rotation in sync with Coordinated Universal Time.

Agnew wrote that the overall acceleration of the planet’s rotation might require timekeepers to insert a “negative leap second” at the end of 2026, however because of climate change, this may not be necessary until 2029.

This is because while the Earth's rotation has been speeding up overall, the melting of ice at high latitudes slows it down.

When the ice masses in Greenland and Antarctica melt, water from the Polar Regions flows into the world's oceans—and especially into the equatorial region. As the water spreads out over the ocean, it increases Earth's 'resistance' to angular acceleration.

More leaps and bounds

“This means that a shift in mass is taking place, and this is affecting the Earth's rotation,” Benedikt Soja, Professor of Space Geodesy at the Department of Civil, Environmental and Geomatic Engineering at ETH Zurich tells Phys Org. “It's like when a figure skater does a pirouette, first holding her arms close to her body and then stretching them out.” The initially fast rotation becomes slower because the masses move away from the axis of rotation, increasing physical inertia.

Soja’s team have published two separate studies in Nature Geoscience and Proceedings of the National Academy of Sciences on how climate change affects the polar motion and the length of the day. Using AI, they have been able to fully explain the various causes of long-term polar motion in the most comprehensive modeling to date.

Their model and their observations show that climate change and global warming will have a greater influence on the Earth's rotational speed than the effect of the moon, which has determined the increase in the length of the day for billions of years.

What Else We Are Wandering

🌏 Core problem
Could Antarctica’s polar vortex be about to split in two? Possibly, reports New Scientist. For the first time in more than 20 years, a series of sudden spikes in stratospheric temperatures could lead to significant warming in Antarctica and unusually hot Australian summers. ‘The southern polar vortex is a clockwise swirl of winds that trap a cold air current above Antarctica during the southern hemisphere winter. The vortex is usually very stable at this time of year, with temperatures inside its core in the stratosphere normally being about -80°C (-112°F).’

There are growing signs that this year’s vortex is increasingly unstable. Wind speeds slowed and allowed cold air to descend, which triggered a record spike in stratospheric temperatures. “As a result, the vortex has been pushed out of its place above the South Pole, causing cold polar air at the surface to seep out towards Australia, New Zealand and South America, and warm air to creep over Antarctica, causing a heatwave on the continent.”

Simon Lee, a Lecturer in Atmospheric Science in the School of Earth and Environmental Sciences at the University of St Andrews, says even relatively small disruptions to the vortex can have a cumulative effect. “Sometimes minor warmings can set the vortex up for something major later on,” he told New Scientist. “Because Antarctic vortex variability is small, if something even slightly unusual happens it can very quickly grow to become an extreme event.”

🌊 The ocean in the core
A major revelation: Where there’s mountains, there’s ocean. An ancient ocean floor was found that scientists at the University of Alabama and Arizona State University say wraps around Earth’s core. This thin but dense layer exists around 1,800 miles below the surface, at the point where the outer core meets the rocky mantle above it. Published in Science Advances the team used seismic waves to create the most high-resolution map yet of the interior structure beneath Earth's Southern Hemisphere.

🔍 All helium is breaking loose
Primordial helium gas may be leaking from Earth’s core, say scientists who found extremely high helium isotope ratios in lavas on Baffin Island in Canada. This is the latest evidence supporting the hypothesis that primordial “reservoirs” of helium and other elements were trapped in Earth’s core in when the young sun and protoplanets coalesced from a cloud of gas and dust more than 4.5 billion years ago, writes Scientific American. It suggests that helium trapped in Earth’s core could be slowly “leaking” into the mantle and then reaching the surface. The findings “suggest that somewhere in the deep portions of our planet, gases are preserved from Earth’s formation,” says the new study’s lead author Forrest Horton, a geochemist at the Woods Hole Oceanographic Institution. The study was published in Nature.

🔍 That 2070’s show
Want to know how your city feels in the future? From the Scandinavian Riviera to ‘Hollywood Becomes Bollywood’, this interactive weather project shows 70 global cities and tracks their climate classification from today until 2070. Click here for your weather forecast.

🌏 Hollow Earthers
Empty day on your hands? Fill your mind with the nonsensical hollow earth theory. You haven’t heard how extraterrestrials are holed up in a huge world in the empty centre of Earth? Oh now you want to go. Sure, it’s the first door in the North Polar opening. If you miss that, take the smaller one in the South.

🌏 Cardboard calculations:
Inge Lehmann, Discoverer of the Earth’s Inner Core
Born in Denmark in 1888, Lehmann, a Danish Seismologist, was a pioneer among women and scientists. Her nephew recalls, “I remember Inge one Sunday in her beloved garden…with a big table filled with cardboard oatmeal boxes. In the boxes were cardboard cards with information on earthquakes…all over the world. This was before computer processing was available, but the system was the same. With her cardboard cards and her oatmeal boxes, Inge registered the velocity of propagation of the earthquakes to all parts of the globe. By means of this information, she deduced new theories of the inner parts of the Earth.”

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