French researchers have proposed a new hypothesis to explain the reversal of the magnetic field of the Earth uneven distribution of lithospheric plates.
Earth's magnetic field — the result of the movement of molten iron that makes up the outer core of our planet. It has long been known that the magnetic field, including the position of the magnetic poles, permanent. Moreover, in the Earth's history there have been periods when there is an inversion of the magnetic field. This process can take a few thousand years, at which time the magnetic field structure is complicated and differs significantly from our usual dipole field, then north and south magnetic poles switch places.
Using paleomagnetic dating, it was found that such an inversion took place many times, and for periods of frequent change of poles followed tens of millions of years of relatively quiet state of the magnetic field, from which it can be concluded about the random nature of the process. Last inversion completed 780 thousand years ago.
So far, the hypothesis put forward to explain the coup poles for the movements in the outer core (see, for example, scientific and popular articles.) Using computer simulations have shown that the fluctuations in the flow of liquid metal in the core can lead to reversal of the magnetic field. However, the new work of the team from the National Centre for Scientific Research (CNRS, France), soon to be published in the journal Geophysical Research Letters, a rather unexpected offered a theory about the relationship between the inversion of the poles and the location of lithospheric plates.
The researchers found that the reversal of the magnetic field was preceded by the uneven distribution of plates, when they, for example, concentrated in one hemisphere. When they were located more or less uniformly, poles coup occurred. "We can see quite clearly that the location of the continents on the Earth's surface due to the reversal frequency of the magnetic field," — says a member of the research group Petrella Francois (Francois Petrelis).
However, the hypothesis has a few flaws, so, its scope does not fit into the third period without inversion, which occurred 490-460 million years ago, during which the continents are located mainly in the southern hemisphere. However, he, Mr. Petrella explains this by saying that we can hardly judge the distribution of continents in the too distant past, to draw any conclusions. The second problem is that researchers have failed to explain the relationship between the detected movement of the continents, that is what is happening on the ground, and the outer core, the flow of molten metal which directly affect the magnetic field. As one of the options is assumed that mediate this interaction between the surface and the core is the mantle. But, according to Francois Petrella, check it very difficult because you need a precise description of the processes occurring in the mantle.