Which Way is North?
by Carol Mack
Children --- before the days of satellites and hand-held GPS units, many of us relied on compasses to find our way through the woods. These curious, ancient instruments use a magnetized needle that aligns with magnetic forces of the earth, pointing the way north. But there is a big problem. Magnetic north is not the same as true north, and the difference (called declination) varies significantly, depended where on Earth you stand.
Earth’s magnetic fields not only vary from location to location; they also vary in time. In the Newport area fifteen years ago—back in the dark ages before GPS—we set our compass declinations at 20.5 degrees east. (From our position, magnetic north is east of true north.) Currently, the declination here is 16.5 degrees east. If you haven’t made the adjustment, the four degree error could get you lost quickly, should your GPS batteries die.
Changes in geomagnetism may happen rapidly or slowly, and they are not very predictable—a source of frustration for explorers and navigators through the ages. Geologists tell us there have even been times in the Earth’s past when the magnetic poles deviated far enough to completely reverse, and North became South. This last happened about 780,000 years ago, but intervals between reversals have been as short at 10,000 years. If we were to experience such a reversal, our compasses would not be of much use since magnetic fields weaken drastically during the process. But the GPS unit probably wouldn’t work very well either, due to disruption from increased magnetic storms. On the bright side, we would be treated to wonderful displays of Northern
(or Southern) Lights.
Who keeps track of all these changes in geomagnetism? Fourteen observatories are spread across the United States and its territories—and one happens to be in our own backyard. The Newport Geophysical Observatory, located on the Colville National Forest near Bead Lake has recorded such phenomena since 1966. You can access a real-time readout of our local magnetic attraction at this website: http://geomag.usgs.gov/observatories/newport/. This website will also will link you to more information on geomagnetism, and a calculator to find the current declination setting for that compass (if you are still using it). Or, as explorers like David Thompson must have done, you can wait for a clear night and adjust your compass by the position of Polaris, the North Star—which remains unaffected by magnetic changes on our small planet.