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Science Frontiers ONLINE No. 101: Sep-Oct 1995 |
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"ALMOST INCONCEIVABLE" CHANGES IN THE GEOMAGNETIC FIELD
A decade ago, a trio of geophysicists published a group of papers based on their measurements of the remnant magnetism of the 16-million-year-old layered lava flows at Steens Mountain, Oregon. (SF#45) At that time, they claimed that these finely bedded lava flows testified that, during a field reversal, the earth's field swung around at the astonishing rate of 3° per day! This rate is about one thousand times the current rate of polar drift. Mainstream geophysicists could not believe the 3°/day figure because it implied incredibly rapid changes in the flow of those molten materials within the earth that supposedly generate the geomagnetic field. The Steens Mountain data were "tabled"; that is, dismissed.
The three researchers, though, continued their labors at Steens Mountain and have now offered additional, even more impressive data. They now find that the geomagnetic field probably shifted as much as 6° in a single day. Their work has been carried forward so professionally and meticulously that other scientists are finding their conclusions harder and harder to dismiss. Instead, the search is on for explanations of the rapid field changes. Three possibilities have been advanced -- all of them unpalatable to geophysicists:
- The Steens Mountain rocks are not faithful recorders of the main geomagnetic field. Should this be actually so, the whole field of paleomagnetism, including plate tectonics, is undermined, for it depends upon similar measurements.
- The earth's molten core can change rapidly, at least in some regions, in response to forces still unrecognized. This, of course, is not really a satisfying "explanation."
- The dynamo theory of the origin of the geomagnetic field is incorrect.
(Coe, R.S., et al; "New Evidence for Extraordinarily Rapid Change of the Geomagnetic Field during a Reversal," Nature, 374:687, 1995. Merrill, Ronald T.; "Principle of Least Astonishment," Nature, 374:674, 1995.)
Reference. More puzzles of the geomagnetic field are provided in: Inner Earth. For details, visit: here.