Astronomy

Reversal of magnetic poles of earth

Reversal of magnetic poles of earth


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When the magnetic poles of the earth get reversed, does the earth keep on revolving in the same direction or does it start revolving in the opposite direction?


The Earth will keep revolving in the same direction during a geomagnetic reversal.

There have been a few articles about this phenomenon published during 2018:

National Geographic - No, We're Not All Doomed by Earth's Magnetic Field Flip

Science Daily - Earth's magnetic field is not about to reverse

The Conversation - The Earth's magnetic field reverses more often - now we know why


I had sought an answer from Dr. Christopher S. Baird and am forwarding his answer. That is incorrect. At present, the north geographic pole points toward the North Star, and the south magnetic pole points approximately toward the North Star. After the next reversal, the south magnetic pole will point away from Antarctica.

When the magnetic poles flip, it will have zero effect on the physical orientation of the earth or the location of its geographic poles. The north geographic pole will still be in the arctic near Canada and point towards the North Star, and the south geographic pole will still be in Antarctica. The rotation of the earth (which determines the geographic poles) has a slight, indirect, complicated influence on the spiraling flow of earth's liquid outer core (which determines the magnetic poles). That is why the geographic poles and magnetic poles are close to being aligned. However, the spiraling flow of earth's liquid core has no effect on earth's overall rotation. This means that changes to the earth's magnetic field do not affect the earth's overall rotation. The sun will still rise in the East.


Ice age polarity reversal was global event: Extremely brief reversal of geomagnetic field, climate variability, and super volcano

Some 41,000 years ago, a complete and rapid reversal of the geomagnetic field occured. Magnetic studies of the GFZ German Research Centre for Geosciences on sediment cores from the Black Sea show that during this period, during the last ice age, a compass at the Black Sea would have pointed to the south instead of north.

Moreover, data obtained by the research team formed around GFZ researchers Dr. Norbert Nowaczyk and Prof. Helge Arz, together with additional data from other studies in the North Atlantic, the South Pacific and Hawaii, prove that this polarity reversal was a global event. Their results are published in the latest issue of the scientific journal Earth and Planetary Science Letters.

What is remarkable is the speed of the reversal: "The field geometry of reversed polarity, with field lines pointing into the opposite direction when compared to today's configuration, lasted for only about 440 years, and it was associated with a field strength that was only one quarter of today's field," explains Norbert Nowaczyk. "The actual polarity changes lasted only 250 years. In terms of geological time scales, that is very fast." During this period, the field was even weaker, with only 5% of today's field strength. As a consequence, Earth nearly completely lost its protection shield against hard cosmic rays, leading to a significantly increased radiation exposure.

This is documented by peaks of radioactive beryllium ( 10 Be) in ice cores from this time, recovered from the Greenland ice sheet. 10 Be as well as radioactive carbon ( 14 C) is caused by the collision of high-energy protons from space with atoms of the atmosphere.

The Laschamp event

The polarity reversal now found with the magnetisation of Black Sea sediments has already been known for 45 years. It was first discovered after the analysis of the magnetisation of several lava flows near the village Laschamp near Clermont-Ferrand in the Massif Central, which differed significantly from today's direction of the geomagnetic field. Since then, this geomagnetic feature is known as the 'Laschamp event'. However, the data of the Massif Central represent only some point readings of the geomagnetic field during the last ice age, whereas the new data from the Black Sea give a complete image of geomagnetic field variability at a high temporal resolution.

Abrupt climate changes and a super volcano

Besides giving evidence for a geomagnetic field reversal 41,000 years ago, the geoscientists from Potsdam discovered numerous abrupt climate changes during the last ice age in the analysed cores from the Black Sea, as it was already known from the Greenland ice cores. This ultimately allowed a high precision synchronisation of the two data records from the Black Sea and Greenland.

The largest volcanic eruption on the Northern hemisphere in the past 100,000 years, namely the eruption of the super volcano 39,400 years ago in the area of today's Phlegraean Fields near Naples, Italy, is also documented within the studied sediments from the Black Sea. The ashes of this eruption, during which about 350 cubic kilometers of rock and lava were ejected, were distributed over the entire eastern Mediterranean and up to central Russia.

These three extreme scenarios, a short and fast reversal of Earth's magnetic field, short-term climate variability of the last ice age and the volcanic eruption in Italy, have been investigated for the first time in a single geological archive and placed in precise chronological order.


Surprisingly rapid magnetic field reversals pose risks to Earth

A representation of Earth’s magnetic field shows how it extends from the poles in a protective embrace. A stalagmite from a cave in southwestern China holds telltale evidence of a surprisingly fast pole reversal some 98,000 years ago. Image: Peter Reid/NASA

Earth’s magnetic field, which shields the planet from solar radiation, periodically reverses, with magnetic south becoming magnetic north and vice versa. Such field reversals were thought to occur over thousands of years, but new research shows at least one happened in just two centuries or so when the magnetic field’s strength was reduced by 90 percent.

Such an event in today’s electronically interconnected world could cost trillions in damage to power and communications systems, the researchers say, while exposing the biosphere to increased levels of solar radiation.

“Earth’s magnetic field, which has existed for at least 3.45 billion years, provides a shield from the direct impact of solar radiation,” said Andrew Roberts of the Australian National University’s Research School of Earth Sciences. “Even with Earth’s strong magnetic field today, we’re still susceptible to solar storms that can damage our electricity-based society.”

Roberts and a team of researchers led by Chuan-Chou Shen at the National Taiwan University and lead author Dr Yu-Min Chou of the Southern University of Science and Technology in China carried out precise radiometric dating of a stalagmite from a cave in southwestern China that recorded paleomagnetic changes dating from 107,000 to 91,000 years ago.

The team noted evidence for field reversals that occurred over a few centuries to several thousand years “indicating prolonged geodynamo instability.”

“One surprisingly abrupt centennial reversal transition occurred in 144 ± 58 years and provides unprecedented evidence that raises fundamental questions about the speed of geomagnetic field shifts,” notes an introduction to the paper in the Proceedings of the National Academy of Sciences of the United States.

“Such rapid polarity changes could severely affect satellites and human society in the future if the current geomagnetic field intensity continues to decrease.”


Upheaval and extinctions linked to magnetic reversal 42,000 years ago

A new international study suggests that a magnetic field reversal – combined with changing solar winds – contributed to an environmental crisis and mass extinctions 42,000 years ago. It happened around the time of the demise of the Neanderthals, an extinct human species that once roamed what’s now Europe, these scientists said, and it would have come with electrical storms, widespread auroras and an influx of cosmic radiation. One of the researchers in the video above commented:

… it would have been incredibly scary.

The study’s authors have named this catastrophic time period the Adams Transitional Geomagnetic Event, or Adams Event, a reference to a trope created by Douglas Adams, author of the comedy science fiction series The Hitchhiker’s Guide to the Galaxy. Adams famously wrote that 42 was the answer to:

The University of New South Wales (UNSW) Sydney, and the South Australian Museum co-led the study, which was published on February 19, 2021, in the peer-reviewed journal Science. As Chris Turney of UNSW – a study co-author – explained in a statement:

Earth’s magnetic field dropped to only 0 to 6% strength during the Adams Event. We essentially had no magnetic field at all. Our cosmic radiation shield was totally gone.

As the magnetic reversal of 42,000 years ago helped bring about earthly extinctions, these scientists said, the skies would have been lit by widespread auroras. These scientists suggest the reversal could help explain evolutionary mysteries, such as the extinction of Neanderthals. Image via Unsplash/ UNSW.

The results were dramatic. Solar flares and galactic cosmic rays ripped up particles in Earth’s atmosphere, ionizing the air and zapping the ozone layer. Our ancestors would have witnessed shocking light shows across the sky both day and night. Aurorae, normally confined to the polar regions, would have spread across the globe. The ionized air would have been a great conductor for electrical storms, increasing their frequency.

The turbulence occurring overhead – and the loss of UV protection from the ozone layer – might explain the sudden emergence of cave art as early humans retreated to caves for protection.

As Science magazine reported on February 18:

… the world was turned upside down – at least magnetically speaking.

The oldest cave art known in Europe, around 42,000 years old, is in El Castillo cave in Spain. These red handprints may be related to an ancient form of sunscreen. Image via Paul Pettitt/ Gobierno de Cantabria/ UNSW.

Trees were the key to the mystery

The kauri tree, largest tree species in New Zealand, was the key to understanding this ancient environmental crisis. Sometimes called the God of the Forest, kauri trees make up some of the most ancient forests in the world. A 60-ton trunk from a kauri tree was found several years ago by workers breaking ground for a power plant in New Zealand. The tree, which had been preserved in a bog, turned out to be 42,000 years old and a valuable time capsule for scientists. Its rings spanned some 1,700 years and captured the magnetic reversal.

This brief magnetic reversal had been known before, but, previously, its earthly effects were thought to be mild. The event was discovered in the 1960s in the Laschamps lava flows in Clermont-Ferrand, France, made evident in magnetic studies of the ancient lava. This magnetic reversal was brief it was what scientists called an excursion: not a lasting change in Earth’s magnetic field, but just a temporary change. As you may know, Earth’s magnetic north and south poles are not fixed or tied to Earth’s rotational axes. The magnetic poles wander and wobble and, occasionally, swap places entirely, as appears to have happened temporarily 41,000 to 42,000 years ago. This particular temporary switch lasted for about 800 years before reverting. It’s now called the Laschamps Event, or the Laschamp excursion.

This ancient kauri log lived during the Adams Event. Image via Nelson Parker.

For the first time ever, we have been able to precisely date the timing and environmental impacts of the last magnetic pole switch. The findings were made possible with ancient New Zealand kauri trees, which have been preserved in sediments for over 40,000 years. Using the ancient trees we could measure and date the spike in atmospheric radiocarbon levels caused by the collapse of Earth’s magnetic field.

So the Laschamp Event refers to the magnetic pole reversal itself. The new term used by scientists in 2021 – the Adams Event – refers more broadly to effects on Earth during that time. Earth appears to have undergone an increase in aurorae, electrical storms and cosmic radiation, causing an increase in atmospheric radiocarbon levels. The researchers have tied these events to the extinction 42,000 years ago of megafauna across mainland Australia and Tasmania.

Scientists have done many studies about the breakdown during the Laschamp Event. The new study focused on the time period preceding the Laschamp Event, as the magnetic fields migrated across Earth to their opposite positions. The scientists found that this period is when earthly turmoil was at its greatest.

By studying the kauri tree, researchers were able to create a more detailed timeline of the Laschamp Event. As Alan Cooper of the South Australian Museum further explained:

The kauri trees are like the Rosetta Stone, helping us tie together records of environmental change in caves, ice cores and peat bogs around the world.

Could it happen today?

Some evidence suggests a change in the orientation of Earth’s magnetic field is already underway. Scientists have tracked the north magnetic pole wandering more rapidly in recent years than in the past. And in the last 170 years, the Earth’s magnetic field has weakened by about 9%.

Modern society’s reliance on the electric grid and satellites has all the makings for a dystopian novel come to life, if incoming radiation destroys our sources of power and communication. The issue of climate change adds an extra element of disaster, according to Turney:

Our atmosphere is already filled with carbon at levels never seen by humanity before. A magnetic pole reversal or extreme change in sun activity would be unprecedented climate-change accelerants. We urgently need to get carbon emissions down before such a random event happens again.

Bottom line: Radiocarbon dating in kauri trees helped researchers tie the magnetic field reversal 42,000 years ago to environmental calamities and extinction events.


The Metaphysical Effects Of A Magnetic Pole Reversal

Science has proven that the Earth is currently going through a magnetic pole reversal, so how will this affect us? By analyzing the magnetic fields of lava, we can determine that the last magnetic pole reversal was about 780,000 years ago. While the fossil records do not show any dramatic changes in animal or plant life, more subtle change may have occurred.

Neanderthal extinction?

While the fossil records of animal and plant life do not show any significant changes, John Tarduno, professor of geophysics at the University of Rochester, proposed a direct link between the Neanderthals demise and a significant decrease of geomagnetic field intensity which occurred at the same exact period.

Additionally, according to Monika Korte, the scientific director of the Niemegk Geomagnetic Observatory at GFZ Potsdam in Germany:

“It’s not a sudden flip, but a slow process, during which the field strength becomes weak, very probably the field becomes more complex and might show more than two poles for a while, and then builds up in strength and (aligns) in the opposite direction.”

Ozone layer

One thing to be considered is what will happen to our protective magnetic field around this planet if the pole shift were to happen. Holes within the ozone layer would appear with a lessened magnetic protection. In this scenario, the Earth would be extremely vulnerable to coronal mass ejections, cosmic rays and solar flares, which would lead to solar radiation.

Migratory Animals, Sea Life And GPS

Our GPS capabilities would be eliminated until new coordinates were established. Virtually all commercial airlines would be shut down as well.

Migratory animals and birds would be disoriented as well as dolphins, whales and other mammalian sea life.

Most likely, a physical pole shift would NOT accompany a magnetic pole shift, as once again evidenced by the geologic records.

Metaphysical Implications: The Schumann Resonance

The Earth’s heartbeat is known as the Schumann Resonance, which has been recorded at approximately 7.83 cycles per second for presumably thousands of years. In recent years, the Schumann Resonance has been rising and was recently recorded as high as 8.90.

Speculation infers that the Earth may stop rotating once the Schumann Resonance reached 13 cycles per second. At that point, the Earth would stop rotating for 3 days and then start spinning in the opposite direction, causing a magnetic reversal of the poles.

Under this premise, a magnetic pole reversal may affect the way the hemispheres in our brain interact.

Three possible scenarios exist in such a situation:

1. Nothing happens to our brains.
2. The hemispheres of our brains instantly interact with one another, opening up synapses to higher metaphysical abilities.
3. We all go crazy!

It is estimated to take between 1,000 to 10,000 years for a complete magnetic pole reversal to occur. Our current version has been ongoing since the early 1900’s.

While the ultimate completion may not occur for another 900 to 1990 years, its effects may already be seen.

As evidenced in the above video, the full reversal could be decades away or “much closer”. The latest studies from the University of California, Berkeley state that it could take 100 years or less, adding that the current weakening magnetic field will precede the pole flip.

What we can readily observe are the facts:

  • The magnetic poles have been reversing since the early 1900’s
  • The Schumann Resonance has been rising.
  • There has been a recent phenomenon regarding our perception of time. Could this be related to the magnetic pole shift?

If “as above, so below” can be interpreted as, “as within, so without” then we can surmise that major changes are happening both in the cosmos, on our planet and, ultimately, within ourselves.


Tracking a Jurassic reversal of the Earth's magnetic field

Roughly 180 million years ago, during the height of the Jurassic period, the Earth's magnetic field flipped, bringing the magnetic north pole once again into the Northern Hemisphere.

This so-called van Zijl reversal, named for the researcher who first described it, is the second-oldest well-documented geomagnetic reversal. Such perturbations of the Earth's magnetic field, which tend to take place over about 10,000 years, and possibly much less, have been identified as occurring up to several billion, and as recently as 780,000, years ago. An open question exists about the effect of such reversals on the properties of the Earth's magnetic field, including the structure it takes, and the consequent effects on its shape, size, and strength. Drawing on newly identified records of the van Zijl reversal, Moulin et al. describe the serpentine travels of the transitional magnetic pole and the variable strength of the paleomagnetic field.

Analyzing the orientations of magnetic minerals found encased within rock samples drawn from an ancient lava field in Lesotho, a small country encompassed within South Africa, and from another field in South Africa itself, the authors tracked the shifting geographic location of the ancient magnetic pole. They find that over a short period, possibly only a few centuries, the pole leapt from a location oriented around 45 degrees south to one near 45 degrees north. The paleomagnetic pole then drifted through around 20 degrees latitude as it moved to the southeast. Finally, the pole moved to a stable location centered near the geographic north pole. The authors find that leading up to the magnetic reversal, the strength of the magnetic field weakened to roughly 10 - 20 percent of its normal value, a depression that only decayed once the pole's location stabilized.


Magnetic reversal caused massive climate shifts

Scientists link most recent magnetic instability to global environmental change.

About 42,000 years ago, a reversal of the Earth’s magnetic poles triggered massive climate shifts and caused environmental changes to sweep across the globe, according to new Australian-led research.

Scientists have long known that the planet’s magnetic field periodically flips, with the north and south poles switching places. The last known reversal – which was temporary and technically known as the “Laschamps excursion” – occurred 41,000–42,000 years ago. If such an event happened today, it would wreak havoc on satellites and electrical grids, but its environmental impact is less well understood.

This new study, published in Science, suggests that the Laschamps excursion coincides with significant environmental and ecological changes, including growing ice sheets, mass extinctions, and even the rise of cave art.

To learn this, the researchers built a precisely dated atmospheric radiocarbon record using the tree rings of massive subfossil New Zealand kauri trees (Agathis australis) that were alive during this period. Not only did the trees record changes in radiocarbon levels during the pole reversal, but the growth rings also acted as a natural timestamp.

An ancient kauri tree log from Ngāwhā, New Zealand. Credit: Nelson Parker

“For the first time ever, we have been able to precisely date the timing and environmental impacts of the last magnetic pole switch,” says Chris Turney, co-lead author of the study from the University of New South Wales (UNSW).

“Using the ancient trees we could measure, and date, the spike in atmospheric radiocarbon levels caused by the collapse of Earth’s magnetic field.”

This allowed the researchers to build a detailed timeline of how Earth’s atmosphere changed, showing there was a significant increase of radiocarbon during the Laschamps excursion. They compared this with other records of environmental changes from caves, ice cores and peat bogs, and then incorporated it into global climate models to look at the environmental impacts.

Most previous research had focused on what happened during the reversal, when the magnetic field was reduced to 28% of its current strength. But this study reveals the most dramatic impacts occurred into the lead-up to the reversal, when the field dropped to 0–6% of its current strength.

Red ochre –which may have been used as an ancient form of sunscreen –is a common cave art motif. The centre of this cave art from Spain is believed to be almost 42,000 years old. Credit: Paul Pettitt,courtesy Gobierno de Cantabria.

“We essentially had no magnetic field at all – our cosmic radiation shield was totally gone,” Turney explains.

This left the planet vulnerable to solar flares and cosmic rays.

“Unfiltered radiation from space ripped apart air particles in Earth’s atmosphere, separating electrons and emitting light – a process called ionisation,” Turney explains. “The ionised air ‘fried’ the ozone layer, triggering a ripple of climate change across the globe.”

The team posit that the magnetic reversal – and subsequent radiation exposure – may be linked to the growth of ice sheets and glaciers across North America at the time, as well as shifts in major wind belts and tropical storms.

Several other major events also occurred around 42,000 years ago, including the disappearance of Australian megafauna and the extinction of the Neanderthals. Both could be linked to these widespread environmental changes, perhaps partially due to an inability to adapt.

The timing also coincides with the appearance of figurative cave art. The researchers suggest that increased UV radiation from a weak magnetic field may have driven humans to seek more shelter – and may even explain the use of red ochre as early sunscreen.

The lead-up to the Laschamps excursion, the authors write in their paper, “appears to represent a major climatic, environmental, and archaeological boundary that has previously gone largely unrecognized”.

According to Agathe Lisé-Pronovost, a paleomagnetic geologist at the University of Melbourne who was not involved the study, this new research is fascinating because a hypothetical link between the magnetic field and climate is a long-standing question.

“Much of the discussion in the literature has been speculating what processes may possibly link events that happened at about the same time,” she explains. “It remains largely unclear if and how the magnetic field of our planet, which is generated in the outer core, may impact what is happening at the surface.”

This study, she says, is the first of its kind to bring together “new quality data and an original modelling approach”.

UNSW’s Professor Chris Turney at the Chronos 14Carbon-Cycle facility. Credit: UNSW Sydney

It may help provide a framework to study the potential environmental and evolutionary shifts during the last full magnetic reversal, 780,000 years ago – and could help us understand the implications of a future reversal.

Over the past 170 years, the Earth’s magnetic field has weakened by around 9%, leading scientists to speculate that a reversal might be imminent. Increased exposure to solar storms and other cosmic radiation could be devastating to our satellites and electrical infrastructure – and Turney warns it could be devastating to the climate, too.

“Our atmosphere is already filled with carbon at levels never seen by humanity before,” he says. “A magnetic pole reversal or extreme change in Sun activity would be unprecedented climate change accelerants.”


Earth’s last magnetic pole flip took 22,000 years to complete

The Earth has a magnetic field, in many ways similar to a bar magnet.

Hopefully you played with a bar magnet in school. You sprinkle iron filings on a piece of paper and put the magnet underneath and the iron shavings rearrange themselves into a lovely set of curves, converging at the magnetic poles and spreading out more halfway between them. The overall shape is like an apple cut in half.

The Earth has a magnetic north pole and a magnetic south pole (not to be confused with the geographic, or rotational, poles) just like that bar magnet — we call this a dipole field. But the mechanism creating the magnetic fields between the two are way different.

In a bar magnet, it's due to iron atoms each has a small magnetic field, and the atoms themselves are aligned in such a way that they all add together, creating the overall magnetic field.

In the Earth it's far more complicated. The Earth's core is composed of two layers the inner core, which is solid, and the outer core, which is liquid. The core is very hot, and the inner core heats the outer core above it. Heated from below, the liquid in the outer core convects: Hot fluid rises and cooler stuff sinks. But there's iron in the core and it's hot enough to be ionized, to have one or more electrons stripped off, giving atoms a net positive charge. When a charged particle moves it creates a magnetic field, and all those atoms moving in the same direction generate Earth's overall magnetic field.

As long as the Earth's core is hot, that outer core will convect, and the Earth's magnetic field will exist.

The Earth’s overall magnetic field is similar to a bar magnet, with a north and south pole (not to be confused with the geographic poles). Credit: Peter Reid, The University of Edinburgh via NASA

… but it's more complicated than that.

Over a century ago, scientists discovered that Earth's magnetic field sometimes switched polarity, where the north pole becomes the south pole and vice-versa. Mind you, this doesn't mean the Earth physically flips over — that's common refrain by doomsday conspiracy cultists, because they're either easily confused or want to confuse you — just that, say, if you use a compass it'll start pointing south instead of north.

It became clear over time that these reversals have happened many, many times. Almost 200 of them have been seen in the fossil record, going back over 80 million years! They're pretty rare on a human timescale, occurring about once every 100,000 to 1,000,000 years. The thing is, no one is really sure how long they take to go from start to finish. Partly this is because they happened a long time ago — the last one, called the Matuyama-Brunhes reversal, was nearly 800,000 years ago! — and also it's hard to get fine-resolution data, and because they seem to happen rapidly (in a geologic sense).

But a new study has been published looking at volcanic, sedimentary, and ice core records, and the scientist found that, in that most recent event, the whole thing took about 22,000 years, much longer than expected!

The Earth's magnetic field first started weakening about 795,000 years ago. After that it flipped polarity and strengthened, but before it could really settle down again it started to fluctuate and collapse again around 11,000 years later (784,000 years ago). The magnetic field fluctuated for some thousands of years after that, but then flipped polarity again and strengthened around 773,000 years ago, becoming the field we have today. That final flip may have only taken 4,000 years. So, instead of just a clean flip, it looked like it underwent three separate stages where sometimes it was dominated by a dipole field (though not really stable) and other times when it was more chaotic. The whole thing took more than twice as long as previous estimates, too.

Sequence showing a physical model of magnetic reversal, where blue and yellow lines represent magnetic flux toward and away from the Earth, respectively. The field gets tangled and chaotic during a reversal before settling back down (note: final frame is simply first frame flipped over and is meant to be representative, not part of the actual model). Credit: NASA / Gary Glatzmaier / Phil Plait

Their methodology is a bit complicated. In volcanic rock, the Earth's magnetic field is recorded as lava cools iron in the rock orients itself to the Earth's field, and so the geomagnetic field strength and direction can be measured. Radioactive isotopes can be used to date the timings of these events. For sedimentary layers, the amount of sunlight the Earth receives changes on timescales of a few tens of thousands of years due to changes in Earth's orbital shape (the Milankovitch cycles) and this can be seen in deposits of an isotope of oxygen.

My favorite one is from the ice cores. When the Earth's magnetic field is weaker, cosmic rays — super-energetic subatomic particles whizzing around in space at near the speed of light — can slam into our atmosphere. When they hit a nitrogen or oxygen atom nucleus they split the nucleus like a bullet going through a rock the shrapnel from this includes an isotope of beryllium called 10 Be. This then gets deposited in ice, and measured in ice cores, allowing scientists to trace the geomagnetic field that way.

So this is interesting! 22,000 years is a long time on a human scale, of course, but still rapid for a geological event. It's hard to say how representative that is for other reversals, but it's a place to start.

A big question still remains, and that's why this occurs. Hypotheses abound, but overall it's likely that the field gets tangled up inside the Earth after some triggering event, and when it resettles the polarity is reversed.

Another question is what happens during the reversal? Again, a lot of conspiracy theorists love to wax anti-scientific about it, but the truth is no one is really sure. It's likely not to have a huge affect on daily life, though there are bound to be some issues with it — for example, compasses using the Earth's magnetism won't work, but GPS or some equivalent can be used instead. We'll have to be careful though, since Earth's magnetic field protects us from things like the solar wind and cosmic rays, so satellites might be affected. Our thick atmosphere should do a pretty good job protecting us from everything else (like solar wind, cosmic rays, and so on).

One more thing. A lot of breathless headlines are generated when news like this comes around, usually in the "We're overdue for X" variety, whether it's an earthquake, a volcanic eruption, or a magnetic reversal, and generally implying we're all gonna die. The time since the last reversal is somewhat longer than average, but it's not like the planet sets a calendar for these things. It could start tomorrow, or it might not happen for another million years. So until geoscientists say, "Yup, here we go!" breathe easy.


Reversal of magnetic poles of earth - Astronomy

The magnetic field of Earth is shaped like the one you see in a toy bar magnet, but there is a very important difference. The toy magnet field is firmly fixed in the solid body of the magnet and does not change with time, unless you decide to melt the magnet with a blow torch! The Earth's field, however, changes in time. Not only does its strength change, but the direction it is pointing also changes.

Map makers have been aware that the direction of the magnetic field changes since the 1700's. Every few decades, they had to re-draw their maps of harbors and landmarks to record the new compass bearings for places of interest. Think about it. If you are on a ship navigating a harbor in a fog, a slight change in your compass heading can take you into a reef or a sandbar!

Geologists have also been keeping track of the wandering magnetic poles as well. Instead of using compasses, they can actually detect the minute fossil traces of Earth's magnetism in rocks. These rocks are dated to determine when they were formed. From this information, geologists can figure out exactly how Earth's magnetic field has changed during the last two billion years. The results are surprising. Right now, the North point of your compass points towards the magnetic pole in the Northern Hemisphere. That's why compass creators put the 'N' on the tip of the magnetized compass needle. But because opposite's attract, this means that the magnetic pole in the Northern Hemisphere is actually a south magnetic pole! That's because scientists named magnetic polarity after the geographic compass direction!

Since the 1800's, Earth's magnetic South Pole which lives in the Northern Hemisphere has wandered over 1100 kilometers. By the year 2030, the magnetic pole will actually be almost right on top of our geographic North Pole. Then in the next century, it will be in the northern reaches of Siberia! Scientists are excited, and a bit concerned, by the sudden dramatic change in the magnetic pole's location. They worry that something may be going on deep within the Earth to cause these changes, and they have seen this kind of thing happen before.

What geologists have discovered is that the magnetic poles of Earth don't just wander around a little, they actually flip-flop over time. About 800,000 years ago, the Earth's magnetic poles were opposite to the ones we have today. Back then, your compass in the Northern Hemisphere would point to Antarctica, because in the Northern Hemisphere the polarity had changed to 'North' and this would have repelled the North tip of your (magnetized) compass needle. Geologists have discovered in the dating of the rocks that the magnetism of Earth has reversed itself hundreds of times over the last billion years. Careful measurements of rock strata from around the world confirm these reversal events in the same layers, so they really are global events, not just local ones. What is even more interesting is that the time between these magnetic reversals, and how long they last, has changed dramatically. 70 million years ago, when dinosaurs still roamed the landscape, the time between magnetic reversals was about one million years. Each reversal lasted about 500,000 years. 20 million years ago, the time between reversals had shortened to about 330,000 years, and each reversal lasted 220,000 years.

Today, the time between reversals has declined to only about 200,000 years during the last few million years, and each reversal lasts about 100,000 years or so. When did the last reversal happen?

This is a plot of the change in the main field strength of Earth for the last 800,000 years from the research by Yohan Guyodo and Jean-Pierre Valet at the Instuitute de Physique in Paris published in the journal Nature on May 20, 1999 (page 249-252).

The Brunhes-Matuyama Reversal ended 980,000 years ago when the polarity of the field actually did 'flip'. Since that time, the polarity of Earth's field has remained the same as what we measure today with the Northern Hemisphere Arctic Region containing a 'South-Type' magnetic polarity, and the Antarctic Region containing a 'North-type' polarity. You will note that the last reversal ended when the magnetic intensity reached near-zero levels. Since then, there was a near-reversal about 200,000 years ago labeled 'Jamaica/Pringle Falls' after the geologic stratum in which these intensity measurements were first identified. Scientists do not know just how low our field has to fall in intensity before a reversal is triggered, but the threshold seems to be below 2.0 units on the scale of the above 'VADM' plot. Beginning in the 1920's, geologists discovered traces of the last few magnetic reversals in rock samples from around the world. Between 730,000 years ago to today, we have had the current magnetic conditions where the South-type magnetic polarity is located in the Northern Hemisphere near the Arctic. Geologists call this the Brunhes Chron. Between 730,000 to 1,670,000 years ago, Earth's magnetic poles were reversed during what geologists call the Matuyama Chron. This means that the North-type magnetic polarity was found in the Northern Hemisphere. Notice that the time since the last reversal (the end of the Mayuyama Chron) is 730,000 years. This is a LOT longer than the 200,000 years!

Some scientists think that we may be overdue for a magnetic reversal by about 500,000 years!

Is there any evidence that we are headed towards this condition? Scientists think that the sudden, rapid change in our magnetic pole location is one sign of a significant change beginning to occur. Another sign is the actual strength of Earth's magnetic field.

Scientists are convinced that Earth's magnetic field is created by currents flowing in the liquid outer core of Earth. Like the current that flows to create an electromagnet, Earth's currents can change in time causing the field to increase and decrease in intensity. Geological evidence shows that Earth's field used to be twice as strong 1.5 billion years ago as it is today, but like the weather it has gone through many complicated ups and downs that scientists don't have a real good explanation for, or ability to predict. But the fossil evidence does tell us something important.

In the 730,000 years since the last magnetic reversal, Earth's field has at times been as little as 1/6 its current strength. This happened about 200,000 years ago. Also, around 700 AD it was 50% stronger than it is today. There have been many sudden ups and downs in this intensity, but some scientists think that conditions are rapidly becoming very different than the past historical trends have shown.

We've only been able to measure the Earth's magnetic field strength for about two centuries. During this time, there has been a gradual decline in the field strength. In recent years, the rate of decline seems to be accelerating. In the last 150 years, the strength of Earth's field has decreased by 5% per century. This doesn't seem like a very fast decrease, but it is one of the fastest ones that has been verified in the 800,000 year magnetic record we now have. At this rate, in 10 centuries we will be 50% below our current field strength, and after 2000 years we could be at zero-strength. The data on past reversals seems to show that, when the field reaches 10% of its current strength, a magnetic reversal can be triggered. It has been 730,000 years since the last reversal ended. We are certainly long overdue for a reversal, by some statistical estimates.

But the caveat is that magnetic changes come in a variety of timescales from the major reversal events every few hundred thousand years to micro changes called 'excursions' that come and go withing a few thousand years. Two detailed "studies of the geomagnetic field in the last 1 million years have found 14 excursions, large changes in direction lasting 5-10 thousand years each, six of which are established as global phenomena by correlation between different sites. Excursions appear to be a frequent and intrinsic part of the (paleomagnetic) secular variation".(Gubbins, David. 1999. The distinction between geomagnetic excursions and reversals. Geophysical Journal International, Vol. 137, pp. F1-F3.). The figure below shows on the left-side the magnetic intensity measurements since 500,000 years ago during the current Brunhes magnetic chron. You can easily see the 'spiky' fast excursions, but the overall magnetic intensity is decreasing in time to the present day. We may be living inside one of these fast excursions which will be replaced by a growing field in a few thousand years, but it seems that the big picture is still that the overall largescale field is declining slowly over 100,000 year timescles. It isn't the excursions we need to worry about for 'reversals' but this larger trend downwards that seems to be going on.

So, what will happen when the field reverses? The fossil record, and other geological records, seem to say 'Not much!'

Scientists have recovered deep-sea sediment cores from the bottom of the ocean. These sediments record the abundance of oxygen atoms and their most common isotope: Oxygen-18. The increases and decreases in this oxygen isotope track the ebb and flow of periods of global glaciation. What we see is that, during the time when the last reversal happened, there was no obvious change in the glacial conditions or in the way that the conditions came and went. So, at least for the last reversal, there was no obvious change in Earth's temperature other than what geologists see from the 'normal' pattern of glaciation. By the way, because glaciation depends on the tilt of Earth's spin axis, this also means that a magnetic reversal doesn't change the spinning Earth in any measurable way.

Loess deposits in China have recently given climatologists a nearly unbroken, continuous record of climate changes during the last 1,200,000 years. What they found was that the sedimentation record shows the summer monsoons and how severe they are. The only significant variation in the data could be attributed to the coming and going of glacial and inter-glacial periods. So, summer monsoons in China were not affected by the reversal in any way that can be obviously seen in the climate-related data from this period. The fossil record, at least for large animals and plants, is even less spectacular when it comes to seeing changes that can be tied to the magnetic reversal.

The Brunhes-Matuyama reversal happened 730,000 years ago during what paleontologists call the Middle Pleistocene Era (100,000 to 1 million years ago). There were no major changes in plant and animal life during this time, so the magnetic reversal did not lead to planet-wide extinctions, or other calamities that would have impacted existing life. It seems that the biggest stresses to plant and animal life were the comings and goings of the many Pleistocene Ice Ages. This led very rapidly to the evolution of cold-tolerant life forms like Woolly Mammoths, for example.

So, it seems that we may be headed for another magnetic reversal event in perhaps the next few thousand years. This event, based on past fossil and geological history, will not cause planet-wide catastrophies. The biosphere will not become extinct. Radiation from space will not cause horrible mutations everywhere. Ocean tides will not devastate coastal regions, and there will certainly not be volcanic activity that leads to global warming.

Of course, scientists cannot predict which minor effects may take place. A magnetic reversal could be a big nuisance to many organisms that will not lead to their extinction, but it just might lead to temporary changes in the way they would normally conduct themselves. The fossil record doesn't record how a species reacted to minor nuisances! Some animals use Earth's field to magnetically navigate, but we know that these same animals have back-up navigation systems too. Pigeons use Earth's magnetism to navigate, as do dolphins, whales and some insects. They also use their eyes as a backup, and a knowledge of land forms and geography, or the location of the Sun and Moon to get about. Humans have used compasses to navigate for thousands of years, but now we rely almost entirely on satellites to steer by. In the future, only those few anachronistic people using the ancient technology of compasses to get around, would have any problems!

The magnetic field of Earth shields us from cosmic rays, so losing this shield may seem like a big deal, but it really isn't. Cosmic rays are not the same kind of radiation as light, instead it consists of fast-moving particles of matter such as electrons, protons and the nuclei of some atoms. Our atmosphere is actually a far better shield of cosmic radiation than Earth's magnetic field. Losing the magnetic field during a reversal would only increase our natural radiation background exposure on the ground by a small amount - perhaps not more than 10%. The long term result might be a few thousand additional cases of cancer every year, but certainly not the extinction of the human race.

Return to Dr. Odenwald's FAQ page at the Astronomy Cafe Blog. References: Guo, Zhengtang, et al., 2000, "Summer Monsoon Variations Over the Last 1.2 Million Years from the Weathering of Loess-soil Sequences in China", Geophysical Research Letters, June 15, pp. 1751-1754. Guyodo, Yohan and Valet, Jean-Pierre 2003, "Global Changes in Intensity of the Earth's Magnetic Field During the Past 800 kyr", Nature, May 20, 2003, p. 249. Jacobs, J. A., "Reversals of the Earth's Magnetic Field, (pp. 48-50) Jacobs, J. A. "Geomagnetism" Academic Press (pp. 186-89, 215-220, 236-42) Merrill, Ronald, McElhinny, M. and McFadden, P., "The Magnetic Field of the Earth", Academic Press, (pp.120-125) Raymo, M., Oppo, D. W., and Curry, W. 1997, "The Mid-Pleistocene Climate Transition: A deep Sea Carbon Isotopic Perspective", Paleoceanography, August 1997, pp. 546-559. Rikitake, Tsuneji and Honkura, Yoshimori, "Solid Earth Geomagnetism", D. Reidel Publishing Co. (pp. 42-45) Ruddiman, W., et al. 1989, "Pleistocene Evolution: Northern Hemisphere Ice Sheets and North Atlantic Ocean", Paleoceanography, August, pp. 353-412. Wollin, G., Ericson, D., Ryan, W. and Foster, J. 1971, "Magnetism of the Earth and Climate Changes", Earth and Planetary Science Letters, vol. 12, pp. 175-183.


Magnetic pole reversal ahead?

The Earth is blanketed by a magnetic field. It’s what makes compasses point north, and protects our atmosphere from continual bombardment from space by charged particles such as protons. Without a magnetic field, our atmosphere would slowly be stripped away by harmful radiation, and life would almost certainly not exist as it does today.

You might imagine the magnetic field is a timeless, constant aspect of life on Earth, and to some extent you would be right. 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. And when the field flips it also tends to become very weak.

On the left, the Earth’s magnetic field we’re used to. On the right, a model of what the magnetic field might be like during a reversal. Image via NASA/Gary Glazmaier

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.

And the field is continuing to grow weaker, potentially portending even more dramatic events, including a global reversal of the magnetic poles. Such a major change would affect our navigation systems, as well as the transmission of electricity. The spectacle of the northern lights might appear at different latitudes. And because more radiation would reach Earth’s surface under very low field strengths during a global reversal, it also might affect rates of cancer.

We still don’t fully understand what the extent of these effects would be, adding urgency to our investigation. We’re turning to some perhaps unexpected data sources, including 700-year-old African archaeological records, to puzzle it out.

Genesis of the geomagnetic field

Cutaway image of the Earth’s interior. Image via Kelvinsong

Earth’s magnetic field is created by convecting iron in our planet’s liquid outer core. From the wealth of observatory and satellite data that document the magnetic field of recent times, we can model what the field would look like if we had a compass immediately above the Earth’s swirling liquid iron core.

These analyses reveal an astounding feature: There’s a patch of reversed polarity beneath southern Africa at the core-mantle boundary where the liquid iron outer core meets the slightly stiffer part of the Earth’s interior. In this area, the polarity of the field is opposite to the average global magnetic field. If we were able to use a compass deep under southern Africa, we would see that in this unusual patch north actually points south.

This patch is the main culprit creating the South Atlantic Anomaly. In numerical simulations, unusual patches similar to the one beneath southern Africa appear immediately prior to geomagnetic reversals.

The poles have reversed frequently over the history of the planet, but the last reversal is in the distant past, some 780,000 years ago. The rapid decay of the recent magnetic field, and its pattern of decay, naturally raises the question of what was happening prior to the last 160 years.

Archaeomagnetism takes us further back in time

In archaeomagnetic studies, geophysicists team with archaeologists to learn about the past magnetic field. For example, clay used to make pottery contains small amounts of magnetic minerals, such as magnetite. When the clay is heated to make a pot, its magnetic minerals lose any magnetism they may have held. Upon cooling, the magnetic minerals record the direction and intensity of the magnetic field at that time. If one can determine the age of the pot, or the archaeological site from which it came (using radiocarbon dating, for instance), then an archaeomagnetic history can be recovered.

Using this kind of data, we have a partial history of archaeomagnetism for the Northern Hemisphere. In contrast, the Southern Hemisphere archaeomagnetic record is scant. In particular, there have been virtually no data from southern Africa – and that’s the region, along with South America, that might provide the most insight into the history of the reversed core patch creating today’s South Atlantic Anomaly.

But the ancestors of today’s southern Africans, Bantu-speaking metallurgists and farmers who began to migrate into the region between 2,000 and 1,500 years ago, unintentionally left us some clues. These Iron Age people lived in huts built of clay, and stored their grain in hardened clay bins. As the first agriculturists of the Iron Age of southern Africa, they relied heavily on rainfall.

Grain bins of the style used centuries ago. Image via John Tarduno

The communities often responded to times of drought with rituals of cleansing that involved burning mud granaries. This somewhat tragic series of events for these people was ultimately a boon many hundreds of years later for archaeomagnetism. Just as in the case of the firing and cooling of a pot, the clay in these structures recorded Earth’s magnetic field as they cooled. Because the floors of these ancient huts and grain bins can sometimes be found intact, we can sample them to obtain a record of both the direction and strength of their contemporary magnetic field. Each floor is a small magnetic observatory, with its compass frozen in time immediately after burning.

With our colleagues, we’ve focused our sampling on Iron Age village sites that dot the Limpopo River Valley, bordered today by Zimbabwe to the north, Botswana to the west and South Africa to the south.

What’s happening deep within the Earth, beneath the Limpopo River Valley Image via John Tarduno

Magnetic field in flux

Sampling at Limpopo River Valley locations has yielded the first archaeomagnetic history for southern Africa between A.D. 1000 and 1600. What we found reveals a period in the past, near A.D. 1300, when the field in that area was decreasing as rapidly as it is today. Then the intensity increased, albeit at a much slower rate.

The occurrence of two intervals of rapid field decay – one 700 years ago and one today – suggests a recurrent phenomenon. Could the reversed flux patch presently under South Africa have happened regularly, further back in time than our records have shown? If so, why would it occur again in this location?

Over the last decade, researchers have accumulated images from the analyses of earthquakes’ seismic waves. As seismic shear waves move through the Earth’s layers, the speed with which they travel is an indication of the density of the layer. Now we know that a large area of slow seismic shear waves characterizes the core mantle boundary beneath southern Africa.

Location of the South Atlantic Anomaly. Image via Michael Osadicw/John Tarduno

This particular region underneath southern Africa has the somewhat wordy title of the African Large Low Shear Velocity Province. While many wince at the descriptive but jargon-rich name, it is a profound feature that must be tens of millions of years old. While thousands of kilometers across, its boundaries are sharp. Interestingly, the reversed core flux patch is nearly coincident with its eastern edge.

The fact that the present-day reversed core patch and the edge of the African Large Low Shear Velocity Province are physically so close got us thinking. We’ve come up with a model linking the two phenomena. We suggest that the unusual African mantle changes the flow of iron in the core underneath, which in turn changes the way the magnetic field behaves at the edge of the seismic province, and leads to the reversed flux patches.

We speculate that these reversed core patches grow rapidly and then wane more slowly. Occasionally one patch may grow large enough to dominate the magnetic field of the Southern Hemisphere – and the poles reverse.

The conventional idea of reversals is that they can start anywhere in the core. Our conceptual model suggests there may be special places at the core-mantle boundary that promote reversals. We do not yet know if the current field is going to reverse in the next few thousand years, or simply continue to weaken over the next couple of centuries.

But the clues provided by the ancestors of modern-day southern Africans will undoubtedly help us to further develop our proposed mechanism for reversals. If correct, pole reversals may be “Out of Africa.”

John Tarduno, Professor of Geophysics, University of Rochester and Vincent Hare, Postdoctoral Associate in Earth and Environmental Sciences, University of Rochester

This article was originally published on The Conversation. Read the original article.