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geomagnetic reversal |
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geomagnetic reversalAlternation of the Earth's magnetic polarity. The Earth's internal magnetic field reverses, on average, about every 300,000 to 1 million years. This reversal is very sudden on a geologic time scale, apparently taking about 5,000 years. The time between reversals is highly variable, sometimes less than 40,000 years and at other times as long as 35 million years. No regularities or periodicities have yet been discovered. A long interval of one polarity may be followed by a short interval of opposite polarity. See also polar wandering. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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| Scientists aren't sure why magnetic reversals happen. The combination of magnetic data from the ocean basins and onland basalt piles upward of 4-km thick, provides a chance to link magnetic reversals to biostratigraphy and absolute ages from the exposed rock record, and to understand in detail the behaviour of the earth's magnetic field during the reversal process. By prying loose magnetic-field loops anchored to the visible solar surface, coronal mass ejections may sweep the surface clean of old magnetic fields and prepare the sun for its magnetic reversal. |
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