|MadSci Network: Earth Sciences|
We think this happens regularly, but not often, at least not since recorded history began. Our best guess is it last happened about 11,000 years ago, before written records and of course before magnetic media like computer disks. See http://www.madsci.org/posts/archives/nov98/912372013.Es.r.html for more about the earth's magnetic field, and why it may change sometimes. Since nobody has never recorded a magnetic pole switch, we dont know for sure how it happens. How it affects our everyday lives depends greatly on how fast it happens. The sun changes magnetic poles every 11 years, it happens slowly and we can watch the sunspots multiply and die away during each cycle. If this happened slowly on earth we might not notice much except our magnetic compasses would drift away from true north. We already correct for "magnetic variation" or the difference between magnetic north (the magnetic pole) and true north (the axis of rotation). And we watch this difference change year by year. We are not sure if very sudden changes ever happen. If a large difference in magnetic poles happened very quickly, say, in a few hours or days it could mean big trouble for electric power grids and radio communications. The sun often ejects bubbles of energy that change the magnetic field of the earth, sometimes enough to cause troubles. We dont see "storms" like tornadoes, but "magnetic storms" my be undetected by our human senses but still cause big problems with electricity and communications. One problem is that big, slow electrical currents flow inside the earth. Our power grids use the earth as a "GROUND" so these currents get into the power grid and cause transformer cores to saturate, and circuit breakers to trip off. Sometimes big electric power companies hire forecasters to help them wait for a calm between the storms to put new power plants on line. These storms are a less than 1% of the total earth field, so you can imagine the power companies would have a trouble delivering their power if the whole earth field changed very suddenly. So far we think the changes are slow enough to handle, but we could get a big surprise one day ! If a change happened suddenly enough, yes, there could be earthquakes. The study of these phenomena and attempts to predict future changes are very important.
Try the links in the MadSci Library for more information on Earth Sciences.