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The Magnetic Field will Change its Mind 8 March 2004 The
time it takes for Earth's magnetic field to reverse polarity is
approximately 7000 years, but the time it takes for the reversal to occur
is shorter at low latitudes than at high latitudes, a geologist funded by
the National Science Foundation (NSF) has concluded. Brad Clement of Einstein once wrote that one of the most important unsolved problems in physics centred around Earth’s magnetic field. Our planet’s magnetic field varies with time; it is indicating it is not a static or fixed feature. Some active processes generate the magnetic field, most likely convecting and flowing liquid iron in Earth’s outer core, geologists believe. Finding what happens as the field reverses polarity is difficult. “It is generally accepted that during a reversal the geomagnetic filed decreases to about 10% of its full polarity value”, said Clement. “ After the field has weakened, the directions undergo 180 degrees change, and then the field strengthens in the opposite polarity direction..”. As to how long this process takes, scientists are forced to answer with a vague “a few thousand years”. Studying deep-ocean sediment cores, Clement has found that magnetic field reversal events occur within certain time-frames, regardless of the polarity of the reversal. The overall average duration, he found, is 7, 000 years. And directional change takes half as long at low-latitude sites as it does at mid- to high-latitude sites. |