An Andy Warhol Moment for Liverpool’s Geomagnetism Group?

Pop-artist Andy Warhol famously stated that: “In the future, everyone will be world-famous for 15 minutes”. I suspect that yesterday may be the closest we will ever get to proving him right.

A paper The birth of the inner coreon which I am lead-author claims that we have may have pinned down the point in Earth’s history when the inner core first started to freeze at the centre of the Earth to between 1 and 1.5 billion years ago.  I already thought this was big news so was a bit deflated when Nature decided not to run with the excellent picture (left) created by Kay Lancaster (cartographer at the University of Liverpool) on its cover or even feature it in its press release.

Nevertheless, our excellent press officer at Liverpool helped produce a great press release which saw a story featured on the popular website from the outset and an article in one of Spain’s top newspapers El Pais.

Things were a bit slow-burning for a while – except in India and Finland. Then the break-though – a beautiful piece by Simon Redfern for BBC news online! I checked and it was even linked to the front page of BBC news (though you did have to scroll down a LONG way to get it…).

This was quickly followed up by a piece on the Daily Mail which our press officer tells me is the “most read online news site in the world”. A number of other things have followed including a post on one of my favourite blogs – IFLScience.

Then, just as I was packing up to go home, I received a phone call from the BBC World Service who wanted a short interview. I obliged in the evening and my nervous responses aired a few hours later. You can listen to the podcast here (it is the very last feature – “And finally…”). They refer before and after the interview to the finding as being that the magnetic field is much older than previously thought – incorrect in this specific case but relevant to another recent finding, albeit one that Liverpool people were not involved in making.

More informative is a piece I wrote for “The Conversation”. There has only been one, “interesting” comment at the time of writing – hopefully things will improve…

A summary from our press office indicates that there are 39 news outlets and counting featuring the story  and tweets still coming through every few minutes. The coverage extends over at least 11 countries ranging from USA to China,  Argentina to Pakistan so, while I can, I am claiming (brief) world fame for our research!


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How do we know the magnetic field comes from inside?

Recently, I received an interesting email from Dmitry who wrote the following:

“According to the Dynamo theory Earth’s magnetic field is generated by rotating, convecting and electrically conducting fluid that maintain a magnetic field.

But what if it creates just by solar wind itself? In this case we don’t need to invent anything else to explain magnetic fields of planets. This process is similar to the principle of electromagnet.

Solar wind magnetizes planets. Now most of it just flies away of the Earth, but a small part of it passes mainly through the north and south poles.

This phenomenon may be also involved in heating the Earth’s core due to the conductor resistance, in the same way as wire is heated when electricity passed through it.”

Let me try to respond to this one piece at a time:

“According to the Dynamo theory Earth’s magnetic field is generated by rotating, convecting and electrically conducting fluid that maintain a magnetic field.”

Spot on – the fluid is in the Earth’s liquid outer core at a depth 2871 km and is convecting because of the release of light elements by the freezing of the inner core beneath it.

“But what if it is created just by the solar wind itself?”

This is already partly true. A small proportion (around 1%) of the Earth’s magnetic field (referred to as the external field) is produced by the interaction of the solar wind (charged particles from the sun) with similar particles within the Earth’s magnetosphere. This part is much weaker, more complex, and changes faster in time than the main part of the field.

“In this case we don’t need to invent anything else to explain magnetic fields of planets.”

Aah but we do. Venus is, in many ways, similar to the Earth and receives more solar wind (being closer to the source) and yet has a field that is 100,000 times weaker than Earth’s. The explanation? No core dynamo. And why not? Difficult to say for certain but likely because the core is not cooling fast enough to fuel a dynamo process.

“Solar wind magnetizes planets.” 

Yes it does but the effect is very small and relatively shallow. A subsurface exploration technique known as magnetotellurics measures the magnetic field induced in the ground by as a consequence of electric currents produced by the solar wind. The measured field variations are typically about 0.001 nT (nano-Tesla) over a period of hours and the resulting electrical currents go to a depth of a few tens of km. Compare this to the main internal field which has an intensity at the surface of around 40,000 nT and seems to come from the core with a depth of nearly 3,000 km. It is a small player.

“Now most of it just flies away of the Earth, but a small part of it passes mainly through the north and south poles.”

All true but the strongest external field variations are felt at the poles because that is where the existing internally-generated field is the steepest. Therefore, it is here that the solar wind particles can most easily travel down the field lines into the atmosphere.


“This phenomenon may be also involved in heating the Earth’s core due to the conductor resistance, in the same way as wire is heated when electricity passed through it.”

The principle here (Ohmic dissipation) is correct but, in practice, I would expect the core heating from this process to be vanishingly small. Pretty much all of the external field will be attenuated by the crust and converted (“dissipated”) to heat generated near the surface so none will be left to penetrate the core. Even close to the surface, the heating effect is very very minor compared to that coming from the Earth’s interior. A back of the envelope calculation gives, very approximately, a heating rate at a few tens of km down of about one-quadrillionth of a degree Celsius per second from these “telluric” currents. Compare this to natural geothermal gradients of tens of degrees per km and you get the picture that this is small-fry indeed.

I hope this post has answered your questions Dmitry and is useful to other readers. I would be very happy to respond to similar emails (or, even better, posts on this website) in the future.

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It’s better to burn out than fade away…well maybe

In a recent post on this blog, Prof. Richard Holme guaranteed us that a field reversal won’t affect human life for “many lifetimes to come”.  This raises the question, how fast can Earth’s magnetic field reverse?  A recent article by an Italian-French-American research team (Sagnotti et al., Geophysical Journal International)  has garnered the attention of the global media over the past couple of weeks (Le Monde, Der Spiegel,   In this study they calculate that the field could change very quickly, just less than 2 degrees per year, i.e. the field could completely flip polarity within a century.  This is very much quicker than the majority of previous estimates, which suggest it takes a few thousand years for a flip to occur, and quicker than the rate of directional changes observed today (a few degrees per century).  Indeed, there is only sparse evidence for such quick changes in the geological record, the most notable being a reversal recorded ~16 Ma in the Steens Mountain lava flows, SE Oregon, and a recent excursion (the Laschamp, ~41 ka) recorded in sediments from the Black Sea.  The Steens Mountain lavas were initially calculated to record changes in the direction of the field up to a phenomenal 3 degrees per day.  However, continued research on the Steens lavas over the last 30 years, headed by Prof. Rob Coe at the University of California-Santa Cruz, led his research group to recently conclude that an interesting phenomena in how the magnetization was acquired by these lavas gave rise to these apparent rapid changes in direction. The directional changes estimated from sediments from the Black Sea were quick (half a degree per year), but quite a bit slower than those from the Sagnotti et al. study and nothing like as fast as those recorded by the Steens Mountain lavas.

How did they reach their result?

The Sagnotti team investigated exposed lake sediments in the Apennines, Italy, covering the time of the most recent geomagnetic field reversal, the Matuyama-Brunhes reversal.  Some debate exists over the age of this reversal, but it occurred approximately 780 ka (this is an ongoing area of fervent research).  As sediments are continually deposited over time they can provide a detailed record of changes in the geomagnetic field depending on how much material is deposited per unit time.  Within these sediments are a number of tephras (ash deposits from volcanic eruptions), which can contain excellent material for radiometric dating, e.g., crystals of sanidine.  In this case researchers from two different labs used the ratio of argon-40 to argon-39 to estimate the ages of the ashes from a large number of experiments on sanidines.  They found the Matuyama-Brunhes reversal lay between two of the dated tephras and by assuming sedimentation was constant between the average ages of their newly determined tephra, estimated the age and the duration of the reversal.  The result: directional changes of just less than 2 degrees per day.

Does this mean the field could completely reverse in less than a human lifetime?

Changes in direction aren’t the whole story.  Although observations on the rate of directional change are interesting, the Earth’s magnetic field has another important component, namely its strength or intensity.  Evidence to date suggests the intensity of Earth’s magnetic field decreases during a reversal and this decrease brackets the polarity flip, but may last considerably longer than the flip itself.  It is likely the decrease in intensity is more intimately linked to underlying processes in Earth’s outer core than the directions themselves, although we don’t exactly know how the reversal process is initiated.  Work done at the University of Liverpool by me and Richard Holme (find here) suggests the length of the polarity flip could be variable depending on the location of the observation, e.g., the duration of the polarity flip could last twice as long in Australia as in Italy, yet the underlying pattern of intensity decrease could be similar. This observation is supported by numerical and empirical modelling of the reversing field.  Even if the polarity flip is short at some locations, the underlying process generating field reversals could be much longer.

In regards to the ability of Earth’s magnetic field to shield Earth from cosmic radiation, it is the strength of the field as well as its configuration that is important, and the field doesn’t fully vanish during a reversal.  Earth’s atmosphere also does a sterling job of protecting the Earth.  It is important to remember the genus Homo have lived through a number of reversals and excursions of the geomagnetic field, such as the Matuyama-Brunhes reversal and more recently the Laschamp excursion.

Is it better to burn out than fade away?  Some reversals may live hard and fast and others may like the quiet life.

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From Russia with Rocks (and a suitcase full of prezzies…)

IMAG0432I have just returned from my first trip to Russia and the Moscow and Borok Labs. There was originally supposed to be fieldwork in southern Siberia this Summer: sampling rocks with the hope they would tell us about the Earth’s magnetic field 400 million years ago. However, a few months back, we discovered that many of the targeted sections have already been studied by the Moscow group. The head of that lab – Vladimir Pavlov – invited me to visit to discuss the work and I gratefully accepted in lieu of the fieldwork. The decision to cancel the sampling trip seems to have been a good one – Vladimir’s colleague Andrey Shatsillo had been there numerous times already and had a stack of data to show me and a sack of samples for me to return with. He also provided samples from some very intriguing sills of a similar age that gave good directions but which were highly anomalous. Vladimir and Andrey shared their opinion that the magnetic field was in a very strange state at this time – an intriguing hypothesis ripe for testing with the equipment at Liverpool and Borok.


Tatyana and Valera in front of Moscow State University where they both graduated from.

In addition to discussing science in Moscow, I enjoyed a Georgian meal with Vladimir and a sightseeing tour given by Tatyana Gendler of the institute. I also gave a seminar in their grand lecture theatre which was translated, slide-by-slide, by Valera Shcherbakov, a rather famous scientist in our area who had come down from his lab in the town of Borok, 350 km to the north. After some sightseeing in Moscow, I accompanied Valera on an overnight train to Borok and spent the remaining 2 days of my trip there. In comparison to cosmopolitan Moscow, Borok and surrounding area felt like the Real Russia. Borok itself has only 2,000 inhabitants but a fascinating history as the only privately owned piece of land in communist Russia. The owner was rather qualified for this honour, a nobleman’s son who had endured 28 years of jail as a communist revolutionary under tsarist rule. In prison, he had developed an interest in the sciences. He founded a biological institute in Borok and other research centres, including a geomagnetic observatory, followed in the ensuing years. Valera and his wife Valentina have been doing research at the palaeomagnetic lab at Borok for 40 years and their group continues to be one of the most prolific in the world.

The Shcherbakov(a)'s

Valera and Valentina Shcherbakov(a)

I had never met Valentina Shcherbakova before but had read many of her papers. She had already measured samples from Devonian collections that I was interested in so we pooled data and discussed a further measurement plan. She provided me with still more samples so that we can compare data obtained using the different methods in place at Liverpool and Borok. Valentina and Valera were also extremely kind in showing me the local area and giving gifts. I told them about my wife’s wish that I return with a book of classic Russian literature (in Cyrillic script). I left with five including two children’s books for my son. Not only this, Valentina handed me a beautiful patchwork quilt she had made herself to give to Brigid. Overall, it was a wonderful trip and it was fortunate that I had arrived with my suitcase only half full!

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So is this it, are we all going to die?


ESA’s magnetic field mission Swarm
Image: ESA

Today’s (7/7/2014) Metro newspaper has a nice article in the Metrocosm section by Ben Gilliland entitled “Portends of magnetogeddon” . Apart from the slight alarmism, it’s (as usual with Ben) pretty good, and I’m pleased to see him talk up the magnetic field even more than I usually do! It seems to be driven by the current ESA satellite mission Swarm, which is measuring the near-Earth magnetic field with the best ever satellite instruments on three separate spacecraft, with a view to separating magnetic sources external to the Earth (like the sun, auroral currents, and the magnetosphere) and those internal (from the core, and from magnetised material at Earth’s surface).  However, much of the article is focussed on more general information, such as magnetic reversals (well known to readers of this blog!) and the possible effects of weakening of the field. That the field is dropping in magnitude is not a new result – we’ve known this for a century or so, and now have evidence that this has been happening for at least 400 years (and probably longer) but it gets a lot of publicity every time we have new measurements – I remember something similar happening when the Ørsted mission was launched in 1999. There was a nice documentary on this over 10 years ago, joint between WGBH Nova for PBS in America, and Channel 4 in the UK called “Magnetic Storm” (“Magnetic flip” in the UK) from which most of the information is still accurate. If you are interested, you can find it online. The issue is that the magnetic field provides us with a shield from harmful solar and cosmic radiation, and so if it weakens (and potentially reverses), this shield would be weakened. However, the answer to the initial question is

Don’t Panic!

(Readers of a certain age may recognise the source of both this response and the slight misquote of the title…..) The answer from the documentary is that the field will weaken, but not completely disappear, it isn’t going to happen for the next 1000 years or so if it does then, and even if it does, the protective measures required will be not to lie on the beach in Florida, and to wear a large floppy hat!

Whether the field is reversing is not known, and (to an extent) not knowable. We have models made from observational data and palaeomagnetic measurements (some created here at Liverpool) which show that in the last 10,000 years, the magnetic field has both decayed more rapidly than it is at present, and been substantially weaker than it is now, but then recovered. Therefore, the current fall in the magnetic field could be simply part of its normal variation. Things are a little more complicated, as there is a strong and growing feature of the “wrong” polarity at the surface of the Earth’s core under the South Atlantic, giving rise to the weaker area of field that we see as the “South Atlantic Anomaly” – which causes occasional havoc in the instruments of satellites flying overhead. This feature could be a signature of a major change in the field, but it could also simply reflect rearrangement of magnetic field at the core – if this becomes more complicated, it could look weaker from the surface without the field itself actually getting any weaker.

What Swarm is really for is getting a much more detailed picture of small-scale structures in the magnetic field, and its rapid changes on time scales of years – so magnetic “weather”, rather than the “climate” of a field reversal. Hopefully, this will give us a much better idea of these smaller variations – my interest is particularly in comparing these variations with changes in Earth rotation.  If this work is successful, we may yet also have something to say about the longer term decline in the field, although I can guarantee that this won’t affect anyone for many lifetimes to come!


Richard Holme

Today’s post was guest written by Richard Holme.   Richard Holme is Professor of Geomagnetism at the University of Liverpool. His research interests are in the behaviour of the magnetic fields of the Earth and other planets on timescales of milliseconds to billions of years, and variations in Earth rotation and their link to Earth’s core. He is involved with the ESA geomagnetic mission Swarm, is looking forward to July 2016 for Juno to arrive at Jupiter, 2017 for Cassini to begin close orbits of Saturn, and 2033 (?!) for the arrival of Juice at Ganymede.

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New paper in G-Cubed to improve consistency in measurements of the ancient magnetic field strength

Geochemistry, Geophysics, Geosystems (G3 or G-Cubed) is an online-only journal of the American Geophysical Union (AGU). It’s format means it is perfect for publishing papers with large supplementary information or appendices. That is definitely the case for this latest publication, lead-authored by Greig Paterson – a Scotsman in Beijing.

Measurements of the strength of the ancient magnetic field recorded in rocks  or archaeological materials (“palaeointensity” or “archaeointensity” measurements) can be very tricky to make. It would therefore be very useful to have some agreement amongst those people doing these experiments about what a reliable measurement looks like.  However, for one reason or another, such consensus has eluded the community for decades. This paper, we hope, is a step towards rectifying that. It uses the largest ever compilation of palaeointensity measurements made using only materials for which we know what the answer “is” (e.g. from lavas that cooled in recent times during which the magnetic field strength is independently known from observatory data). It then finds variants of currently used selection criteria that are better at picking out the reliable measurements than the originals. This stuff may not sound to the outsider as exciting as say, finding a new reversal, but it is the type of thing that underpins palaeomagnetism as a tool for understanding our planet better.

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What is Archaeomagnetism?

Philippe and Valerie taking samples from an archaeolgoical site in France

Philippe and Valerie taking archaeomagnetic samples from a Roman aged achaeological site in France

For regular readers of this blog, the term “archaeomagnetism” will have been seen a number of times, most frequently in posts by me or Andy Herries!

Archaeomagnetism is the study of burnt material found on archaeological sites. This can include everything from hearths, fireplaces and kilns through to tiles, bricks and pottery. Basically anything that has been subjected to heat at some point, either deliberately (e.g. the firing of a pot) or accidently (e.g. if a fire burns down a building, its foundations and walls become suitable for archaeomagnetic study as a consequence).

In certain parts of the world (for specific time periods), it is possible to date archaeological samples by comparing the declination, inclination and intensity values recorded in the archaeomagnetic samples (these 3 values describe the geomagnetic field vector) with the known changes in the geomagnetic field. One of the great things about archaeomagnetism (in my opinion) is the variety of ways in which you can use it. Associate Professor at Liverpool, Andy Herries, focuses on dating Hominid sites in South Africa by dating speolotherms (speolotherms are also known as flow stones and are created through the deposition of carbonate through time. Stalactites and stalagmites form in the same way.) see   It is worth noting that in speoltherms the record of the magnetic field is preserved as a chemical remanant magnetisation rather than a thermal remament magnetisation.

I myself am focused on trying to gather well-dated archeointensity data from Turkey for the dual purpose of enabling archaeomagnetic dating in the future as well as allowing us to accurately reconstruct changes in the geomagnetic field. This work is very interesting because there have been a number of recent papers linking sudden changes in the magnetic field with climate change and civilisation collapse e.g.  I’m investigating whether I can see any evidence for this.

In this post I have only briefly mentioned some of the applications of archaeomagnetism: it is a fascinating field with new methods and ideas being tested every day.

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Killer LIPs? Not so fast…

Certain mass extinction events, including the largest ever 250 million years ago, have been argued to have been triggered by the eruption of “large igneous provinces” (LIPs) – humongous plateaux comprising stacks of lava flows that erupted in relatively short amounts of time.

But how short a time? This is a crucial question as the atmosphere and oceans are pretty effective at processing the gases associated with volcanic eruptions in the short to medium term. So, unless the eruptions occur very close together (i.e. just years apart), there is not really much scope for them causing the kind of long term climate change that can wipe out large fractions of life.

Here at Liverpool, we just published a paper outlining a new tool for getting a handle on eruption rates based on the similarity of the magnetic field direction recorded in cooled lava flows that are on top of one another. The logic goes:

– the Earth’s magnetic field is changing direction all the time (which is why you have to change the declination on your compass every few years)

– when magma erupts and then cools, the magnetic minerals in the newly formed rock lock in a record of this direction

– if neighbouring lavas erupted within a few years of one another then the magnetic field direction will not have changed very much so the directions recorded in them will be quite similar.

This is not a new idea but the paper presents and tests a new parameter for formally quantifying the degree of this “next neighbour correlation”. The new parameter was shown to be an improvement over existing methods and its application to lavas from the  60 million year old “North Atlantic LIP” gave some quite surprising results. There was already independent evidence showing, that in one section of this large igneous province, there were pauses between eruptions that were, on average, several tens of thousands of years  long. Unexpectedly, significant similarity was observed in magnetic directions measured in neighbouring lavas from this section.

Records of palaeomagnetic strength fluctuations over millions of years have already hinted that the magnetic field displays some “correlation” over hundreds of thousands of years (that is, it may be consistently stronger or weaker on average during one period lasting a few hundreds of thousands of years that during another similarly long period). Our new study reports the first evidence that similar “correlation” may be present in the magnetic field direction as well.

Why is this important? Well, in addition to telling us more about the process that generates the Earth’s magnetic field, it also tells us we need to be careful in making the argument that similar palaeomagnetic directions in adjacent lava flows imply very fast eruption rates (as has been done previously). They may not and, with this requirement for rapid lava extrusion reduced, some of the lethality of the “killer LIPs” could be drawn into question too.

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A round-up of some newsworthy geomagnetism stories

This article was originally posted on the EGU Blog network for Geology Jenga.

Happy New Year to you all!

The past few weeks and months have seen some exciting newsworthy stories regarding the Earth’s magnetic field. I thought I’d highlight a few of them for our first post of the New Year.

Magnetic Interactions 2014

For two days in early January, all of us at the Geomag Lab (well, pretty well all of us) travelled to Cambridge University, to attend the UK conference for the geomagnetism community. This year there was also a strong international presence. I would usually write a blog post on the highlights of the research that was being showcased at the conference; however, the meeting organisers beat me to it! Read about the science behind fundamental, applied rock and mineral magnetism, as well as, how an ancient voyage by naturalist Alexander von Humboldt might help us understand the geomagnetic field prior to the 1800s  in this blog post by Dr. Richard Harrison, of Cambridge University.

Logo courtesy of Richard Harrison.

Logo courtesy of Richard Harrison.


The Aurora that never was.

Credit: Wikimedia Commons, user: United States Air Force, This image or file is a work of a U.S. Air Force Airman or employee, taken or made as part of that person's official duties. As a work of the U.S. federal government, the image or file is in the public domain.

Credit: Wikimedia Commons, user: United States Air Force, This image or file is a work of a U.S. Air Force Airman or employee, taken or made as part of that person’s official duties. As a work of the U.S. federal government, the image or file is in the public domain.

On 7th January, there was a large solar flare with an associated fast traveling Coronal Mass Ejection (CME), which was headed straight for the Earth, and was expected to hit our planet by the 9th of January. Space weather scientists, the media and people across the UK and Europe were glued to the night skies in hopes of seeing aurora borealis at abnormally southerly latitudes. Perhaps the excitement surrounding the potential to observe these mysterious phenomena was fueled, at least in the UK, by the timely airing of the first episode of the new series of Star Gazing Live, in which the team (made up of Prof. Brian Cox and comedian Dara O’Brien) took on the challenge to capture the northern lights.

Space weather has featured heavily in the UK media in the run up to the Christmas, as the UK government pledged a £4.6 million investment in the forecast of space weather. From early this year, the Met Office will forecast, deliver alerts and warnings to key sectors that might be adversely affected by  solar flares and CMEs.

Despite the hype, the skies did not deliver. A great blog post by Dr Gemma Kelly, at the geomagnetism team of the British Geological Survey, explains the reasons behind why the Northern lights didn’t quite happen!

For more information on solar flares, CMEs and why they are important: have a look at my guest blog post for GeoSphere on the Earth’s protective shield and also the information pages of the British Geological Survey.


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The magnetic field is fluctuating as it falls…

We just published a new paper lead-authored by Lennart de Groot at Utrecht University who just recently got his PhD “Cum Laude” (quite a distinction).

The paper is online here and I’ve tried to summarise it below.

The Earth’s magnetic field as seen at Earth’s surface is about 90% explained by a “dipole” – a single north pole opposite a single south pole – the same as a bar magnet. The dipole is not stationary but moves around and fluctuates in intensity over time. Occasionally it collapses altogether and grows back with the opposite polarity – this is called a geomagnetic reversal. The last reversal happened 780,000 years ago but there have been many more recent collapses (“geomagnetic excursions”) that haven’t resulted in reversals.

Two of the authors - Lennart and Mark on the top of Mt Etna in 2008.

Two of the authors – Lennart and Mark on the top of Mt Etna in 2008.

The dipole has been weakening steadily (nearly 10%) since the first measurements began in 1840 AD causing some to speculate that we might be heading for a new collapse which would be bad news as magnetic storms might then become more severe. To understand this recent decline, we need to put it in context of magnetic field behaviour before 1840 and for this we have to turn to “accidental” records. The best of these are preserved in baked archaeological materials (e.g. pottery and kiln linings) but these are restricted to locations where complex civilizations existed and this leaves large areas of the globe undocumented.

Records are also preserved in volcanic rocks that have cooled from magma but these are generally much noisier than the archaeological ones because the lavas have less ideal magnetic properties than do pottery. Our study has managed to use a combination of new and old methods to produce a new high quality record from Hawaiian lavas informing us about the behaviour of the field in the sparsely populated Pacific region from around 500 AD to the present.

Combining this new record with other high quality records from archaeological materials recovered from W Europe, Japan, SW USA produces an interesting picture (see figure). As already thought, the recent decline appears to be a continuation of a declining trend going on at least 1,000 year. However, as well as this decline there are also periods of sharply increased intensity in 3 of the records (Hawaii, W Europe, SW USA) but crucially these are at different times in different places (and there is no such peak in Japan). These fluctuations, though large, can’t be explained by the dominant dipole part of the magnetic field as then you would see them everywhere. They must rather be due to the non-dipole field becoming regionally very important in a way that we have not seen since we have been making deliberate records.

Records of the estimated strengh of the main "axial dipole" component of the magnetic field from different locations

Records of the estimated strengh of the main “axial dipole” component of the magnetic field from different locations

The magnetic field is generated by the flow of electrically conducting liquid in the Earth’s outer core and all of these changes reflect the chaotic nature of this flow. In addition to producing records such as these, the challenge lies in producing believable models of core flow to explain the observational data. This might eventually be useful to help predict future magnetic field behaviour.

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