CompuServe Messages

Hi, Michael– Here are some messages from a while back with some bearing here. –Doug #97371 S12/Geology 19-May-93 15:39:54 Sb: Magnetic Field Reversals Fm: James W. Keefer 71562,1543 To: ALL Our earth science class is discussing ocean floor spreading and symmetrical patterns of magnetic reversals on either side of the mid-ocean ridge. What might be the ultimate or proximate cause(s) of magnetic reversals of the earth's field, and how long would a reversal take to complete? jk #97596 S12/Geology 23-May-93 00:55:04 Sb: #97371-Magnetic Field Reversals Fm: Richard Sedlock 71554,1103 To: James W. Keefer 71562,1543 (X) Good questions! The greatest geophysical brains on the planet still haven't come to a concensus, but here are some thoughts that might help you out. If the Earth's magnetic field (EMF) is indeed caused by convection or some other movement of the fluid, iron-rich outer core, then a reversal would seem to require directional changes of that fluid. No one agrees on the size or shape of the convection cells. Reversals can probably occur within a few thousand years, based on careful paleomagnetic rocks of well-dated rocks on land. Problema grande: the huge energy needed to halt the momentum of convecting molten iron in the outer core in a few thousand years, not to mention starting it up again in the other direction. Whoever figures this all out is going to sweep the available physics and geophysics awards. Good luck. rs #97835 S12/Geology 26-May-93 21:40:23 Sb: #97596-Magnetic Field Reversals Fm: Stephen Ryland 72345,366 To: Richard Sedlock 71554,1103 (X) Yes, I think there was a nice summary article in the last few issues of EOS. I think they were making the point that it was longer rather than shorter; a long time ago we used to think it was very fast and could have semi-catastrophic consequences. Steve #99047 S12/Geology 13-Jun-93 23:52:32 Sb: Magnetic Field Reversals Fm: Bill Duxbury 72172,656 This is an area of true possibilities in research. Like so much of the evidence regarding Continental drift, this one opens up as many questions as it answers. The source and amount of energy required to change the direction of a magmatic mass is a mystery. As a pilot, I'm glad to here that the reversal is relatively slow. I would hate to be flying a load of people from Washington D.C. to L.A. when the magnetic poles switched! Our on board navigation systems whould not be happy. Dux #99235 S12/Geology 15-Jun-93 22:39:16 Sb: #99047-Magnetic Field Reversals Fm: Emory Kimbrough (Sysop) 72777,1553 To: Bill Duxbury 72172,656 The current issue of _Science News_ (June 12) has a nice three-page review of the current status of the shouting mat….er….debate on this topic.