People are used to the fact that such large-scale changes as the reshaping of continents or the climate are slow. It is difficult for one generation to appreciate them, but in a couple and just notice. However, here is a discovery: a grandiose event - a reversal of the magnetic poles - can be almost instantaneous even by human standards. And the home planet is able to pull off such a trick before our eyes.
Cycle of inversions
Recently, Scott Baugh of Western College Los Angeles and Jonathan Glen of the US Geological Survey studied ancient igneous rocks in Battle Mountain, Nevada. So American geologists have shown that reversals of the planet's magnetic field can occur thousands of times faster than scientists have assumed until now.
Thanks to the phenomenon of paleomagnetism, a kind of recording of the geomagnetic field in the cooling and crystallizing lava, the researchers found that at the time of the formation of rocks in Battle Mountain (and this happened 15 million years ago), the Earth's magnetic pole shift was 53 degrees in just one year.
According to current ideas, the liquid part of its core is responsible for the formation of the Earth's magnetic field. But the processes in the nucleus are still poorly understood. In this area, researchers continue to discover grandiose phenomena like "digestion" even now.
The figure shows the inner (red) and outer (yellow) core of the Earth, magnetic field lines (blue), metal fluxes (brown lines) caused by the rotation of the core (black arrow), and convective fluxes (light brown arrows) (illustration with website qwickstep.com).
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In that successful (for today's scientists) eruption, the first portion of lava had already frozen ("remembering" the direction of the geomagnetic field), but a year later it was again warmed up by the second outburst of molten rocks, "overwriting" in its upper layer a new direction, which differs by 53 degrees from old.
But, according to current data, the reversal of the magnetic poles takes 4-5 thousand years or even more. This means that the pole shift during such events averages 0.045 degrees per year. But Baugh and Glen believe that polarity reversal can happen much faster, in just four years.
If we superimpose on this hypothesis the first signs that the next shift has already begun, we can conclude: we have a chance to catch one of the most grandiose episodes in the geological history of the planet.
Scientists have been arguing for a long time that the Earth's magnetic field can turn over in the very foreseeable future. And this event is not a catastrophe for the planet, but quite an ordinary process, if you look at it from the point of view of geological eras.
The only question is whether a cataclysm will happen soon according to ordinary human standards, or it is necessary to wait more than one thousand years before a grandiose performance. And how long the inversion itself will take is also a subject of discussion.
The polarity of the geomagnetic field from the present day to the mid-Jurassic period (top) and over the last five million years (bottom). Black areas - polarity, corresponding to today's, white - opposite (illustrations from the site wikipedia.org).
The frequency of polarity reversal of our planet's magnetic poles has varied greatly in the past. You can only roughly deduce the average: the poles turned over every 200-300 thousand years.
At the same time, about 42 million years ago, 17 reversals occurred in three million years, and there was a very long period without reversals, it lasted from 120 to 83 million years ago. And before him there were other long eras without coups.
Therefore, scientists believe that inversion is a rather random process and it is impossible to catch obvious patterns in it. Nevertheless, the last time the "overturning" of the magnetic poles happened as much as 780 thousand years ago. For this reason alone, one can cautiously assume that the planet is preparing for the next such permutation. And then there are a number of indirect signs of impending change.
Is there life after the pole change?
The North magnetic pole of the Earth rushed to Russia: when measuring the rate of its displacement in 2009, scientists received 64 kilometers per year. Meanwhile, in the 1970s, this speed was 10-15 km / year, and only six years ago - about 60. Acceleration is evident.
Over 150 years, the intensity of the geomagnetic field has decreased by about 10%, and in the last 22 years it has dropped by 1.7% (on average, since the changes are far from the same in different regions of the planet). At the same time, the opening angle of the cusps - the polar regions of the field, where the lines of force diverge to the sides - increased.
Stripe magnetic anomalies serve as one of the evidences of reversals of the magnetic field in the past. The rocks pouring out in the oceanic ridges freeze, retaining their magnetization with the current field orientation. Due to the spreading apart of the blocks of the lithosphere, such frozen flows form parallel stripes with alternating magnetization (illustration from the site wikipedia.org).
In general, the Earth's magnetosphere in recent years seems to have begun to "leak". Experts in solar-terrestrial communications speculate about the possibility of stronger than usual magnetic storms and auroras during the peak of solar activity in a cycle that has just begun.
This is not a cause for panic. As it is easy to understand, in the memory of Homo Sapiens, the inversion has not yet happened, but many such events have happened before and life on Earth has not been interrupted.
However, researchers are concerned about the significant field weakening accompanying the pole reversal. Alas, it is still impossible to say finally whether the field will disappear for a while and how long the planet will remain without a magnetic shield.
An example of streak magnetic anomalies in a fault zone near Vancouver Island. The color shows rocks with normal magnetization (coinciding with the modern field), gaps - with reverse magnetization. The scale is in millions of years (illustration from hawaii.edu).
However, if we draw an analogy with the change of the magnetic poles of the Sun (and it happens every 11 years), then the complete loss of our field should not occur, and catastrophic consequences for people and life in general will not happen.
Here, by the way, the super-fast shift, assumed by Scott and Jonathan, plays into our hands. After all, this way we run the risk of being exposed to an increased level of cosmic rays for less time.
The current drift of the pole at 64 kilometers per year is roughly 0.6 degrees per year. Compare that to 53 degrees in the new study. True, it is not known whether it was a short burst against the background of a quieter shift (maybe the ancient eruption caught the very peak of the inversion process) or a complete reversal of the magnetic "north" and "south" really turned out to be so rapid that time. This question is a topic for new research.
The story with the overturning magnetic field is similar to the story of another discovery - the arrival of a powerful glaciation within the last ice age in just six months. It made scientists take a fresh look at how quickly the planet's climate can change from one state to another (frame from cgnews.com).
A coup will restore justice
Not everyone knows, by the way, that the north magnetic pole of the earth in the physical sense is south, and vice versa. There was confusion in this way. When scientists chose the names for the poles of an ordinary magnet, they could give them any names, even plus and minus, at least some abstract letters. But by that time, people had long been using compasses, the arrows of which are dipole magnets. And that end of them, which points to the north, was called the north pole of the magnet (in the original sense, stretching to the north), and the one pointing to the south - the south, But since the opposite poles are attracted by the magnets, it turned out that the earth's magnetic field has a south pole (in the physical sense) is located in the north and is called the "north magnetic pole", and the physical north is in the south.
It is interesting that if the inversion of the earth's field occurs, and the names of the magnetic poles are not changed, justice will be restored with respect to their names.
The figure shows the angle between the axis of rotation of the Earth and the axis of the dipole and the direction of the lines of force (illustration by Peter Reid).
Let's go back, however, a little bit back. Geologists say that the escaping of the poles from their places has happened and more impressive. In 1995, scientists analyzed the remanent magnetization of ancient igneous rocks in Stins Mountain in Oregon and found that the rate of rotation of the planet's magnetic field during the cooling of the lava flow reached an unthinkable six degrees per day. This was several orders of magnitude higher than the rate that science could think of, not counting, of course, the daily fluctuation in the position of the poles caused by the action of charged particles of the solar wind. Therefore, many experts disputed the conclusions of the authors of that work.
But now scientists have discovered a second piece of evidence showing that rapid flips of the geomagnetic field are still possible. Now it would be good to understand whether such instantaneous (by geological standards) field jumps for inversions are common or exceptional.