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article imageEarth's magnetic field could flip within a human lifetime

By Robert Myles     Oct 15, 2014 in Science
Berkeley - Could the world turn upside down — magnetically speaking that is? The answer is yes according to a new joint study by researchers from Europe and America — and a flip of Earth’s magnetic field could occur within our lifetimes.
Such a change would send every magnetic compass on Earth awry, with needles pointing south instead of north.
Historically, it would by no means be the first time Earth’s magnetic field has flipped. Such geomagnetic reversals have happened many times in our planet’s history, though not overnight.
New research into ancient Italian lake sediments shows Earth’s last magnetic reversal 786,000 years ago occurred in less than 100 years.
Earth’s magnetic field works much the same as that of an ordinary dipole magnet. For thousands, even millions, of years, north is north and south is south with the Earth’s magnetic field retaining its same intensity. But for as yet unexplained reasons the planet’s magnetic field sometimes weakens, then over a period of thousands of years it reverses direction.
A new study conducted by a team of scientists drawn from Italy, France, Columbia University and the University of California, Berkeley, found that the last magnetic reversal 786,000 years ago happened over a relatively quick 100 years, barely more than a human lifetime in many countries these days.
The latest research, co-authored by UC Berkeley graduate student Courtney Sprain and Paul Renne, director of the Berkeley Geochronology Center and a UC Berkeley professor-in- residence of Earth and Planetary Science, will be published in the November issue of Geophysical Journal International and is now available online.
New evidence indicates the intensity of Earth's magnetic field is declining 10 times faster than normal. The precipitous rate of decrease has caused some geophysicists to predict a magnetic field reversal within a few thousand years.
Magnetic flip threatens electrical grids, cancer rates
The concept of Earth’s magnetic field reversing polarity may sound apocryphal. It would be a major planet-wide phenomenon driven by convection in Earth's molten iron core. Reassuringly, however, despite thorough research into geological and biological records, there are no major catastrophes in Earth’s past associated with past reversals.
But while the great Earth Mother, Gaia, might well be able to shrug her shoulders and dismiss Earth’s magnetic field flipping as just another reverse polarity event, the same cannot be said of Earth’s modern, man-made adornments or even humankind itself.
Such a reversal has the potential to play havoc with electricity grids, generating currents that could well cause grid outages.
Not only that but since Earth’s magnetic field plays a crucial role in protecting life from high energy particles from the Sun and cosmic rays, any weakening, or worse, temporary loss of the magnetic field could result in such phenomena penetrating to Earth’s surface, resulting in genetic mutations and a rise in cancer rates. If a flipping of the field were preceded by long periods of unstable magnetic behavior, the danger to life would be even greater.
Ancient ash deposits from Italian volcanoes
The latest findings are based on measurements of the magnetic field alignment in layers of ancient lake sediments now exposed in the Sulmona basin of the Apennine Mountains east of Rome, Italy.
These lake sediments are inter-bedded with ash layers that erupted from the Roman volcanic province, a large area of volcanoes upwind of the former lake that includes periodically erupting volcanoes near Sabatini, Vesuvius and the Alban Hills.
Italian researchers headed by Leonardo Sagnotti of Rome's National Institute of Geophysics and Volcanology measured the magnetic field directions frozen into the sediments as they built up on the floor of the ancient lake.
Some of the research team: Left to right  Biaggio Giaccio  Gianluca Sotilli  Courtney Sprain and Seb...
Some of the research team: Left to right, Biaggio Giaccio, Gianluca Sotilli, Courtney Sprain and Sebastien Nomade sitting next to an outcrop in the Sulmona basin of the Apennines that contains the Matuyama-Brunhes magnetic reversal. A layer of volcanic ash interbedded with the lake sediments can be seen above their heads.
Paul Renne, UC Berkeley
To determine the age of layers of ash, argon-argon dating was used, a method in widespread use to pinpoint the ages of rocks, whether thousands or billions of years old. Samples were analysed from above and below the sediment layer recording the last magnetic field reversal.
Because the lake sediments were deposited at a high and constant rate over 10 millenia, the researchers could interpolate the date of the layer showing the magnetic reversal. The last one, known as the Matuyama-Brunhes transition, occurred approximately 786,000 years ago. The date determined by the research team is far more precise than that derived from previous studies that had placed the last reversal at between 770,000 and 795,000 years ago.
"What's incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years," commented Paul Renne.
"We don't know whether the next reversal will occur as suddenly as this one did, but we also don't know that it won't."
Unstable magnetic field preceded 180-degree flip
At this stage it isn’t possible to determine whether the new finding points to the next reversal of polarity posing a danger to civilization in the event of it being a ‘quick’ one occurring over just one century. But the new study should help scientists understand how and why Earth's magnetic field periodically reverses polarity.
The Italian-led research team found that prior to the last sudden 180-degree flip of the magnetic field, Earth experienced a period of magnetic instability spanning more than 6,000 years.
Within these six millennia were two intervals of low magnetic field strength each lasting about 2,000 years.
Rapid changes in field orientations may have occurred within the first low strength interval. The full magnetic polarity reversal, the final and very rapid flip that gave us North in the north as we know it, took place towards the end of the most recent interval of low field strength.
More about earth's magnetic field, Magnetic field, Geophysics, reverse polarity shift, geomagnetic reversal
 
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