April 1996: Magnetic Field Reversal Imminent

A paper to be presented at a scientific conference in London this week could have a profound impact on the future of orienteering. “Predictions of future magnetic field reversals” by Professors Howard Orchard and Alberto Ximenes of the Institute for Applied Physical Research (IAPR) presents the results of a detailed study of movements of the earth’s magnetic poles, and uses these observations to predict that a reversal of the magnetic field is imminent. They claim that the north magnetic pole could move from its current position in northern Canada to a new location in Antarctica over a period as short as one year. The impact on the sport of orienteering, where competitors rely on maps aligned to magnetic north, could be severe.

It has been known for many years that the earth’s magnetic field reverses at regular intervals, with south becoming north and north becoming south. Evidence for this lies in rocks on the sea bed which contain magnetic minerals. As the rocks cool the minerals align to the magnetic field at the time. Characteristic magnetic stripes have been observed in many locations. The new study has examined the sea-bed evidence in detail, allowing new predictions to be made about when the next reversal is due. This has been combined with a detailed study of the movement of the north magnetic pole over the past ten years. Both studies reveal that a reversal is long overdue. Data collected in the first three months of this year show that the north pole is moving increasingly erratically, and ten times faster than last year. The conclusion is that a reversal has started.

The impact on orienteering will be immense. Compasses will continue to point at the north magnetic pole, but its position will be varying. The main problem is that grid lines on maps will need to be corrected. It will become common to run events where the current magnetic north direction must be added as a map correction. Even overprinting the new lines may not be possible because of the difficulty of predicting exactly where the north pole will be on the day the map will be used. Problems will also be caused by the changing angle of dip of the magnetic field. Compass needles are balanced for a given latitude at present, and the moving field will mean that competitors may need to change their compasses frequently. Mapmaking over the coming year may have to be suspended. Without a fixed north point it will prove extremely difficult to correlate field surveys made over a period of days or weeks.

The International Orienteering Federation is expected to announce the formation of an emergency technical committee in the near future to examine the impact of the reversal. This committee may be forced to recommend the cancellation of all World Cup and World Championships events until the pole has finally become stable.

The only other sport which will be influenced significantly is pigeon racing. Pigeons have tiny magnetic particles in their brains, which are believed to allow them to return home over long distances. The moving magnetic field is likely to lead to huge numbers of racing pigeons ending up somewhat confused in the southern hemisphere.