Pole Position! Can You Locate the Magnetic North Pole?
It has long been recognized that the earth’s magentic north and south poles migrate through time. These north and south positions are called dip poles. It is possible to determine the location of the magnetic north pole by conducting a magnetic survey. In 1831, British Naval Officer James Clark Ross determined the location of the north dip pole to be in the Canadian Arctic. Since this time, magnetic surveys have periodically been undertaken to track the pole’s location. The most recent survey indicates that it has moved approcimately 55km per year in a north-northwest direction.
The expeditons at Fort Conger utilized unifiler magnetometers and dip circles to measure the earth’s magnetic field in terms of Intensity, Inclination and Declination.
Intensity. The intensity of the earth’s magentic field is measured in gauss (G), but is generally given in nanotesla (nT) units. The field ranges from 25,000 to 65,000 nT and these values are used to plot intensity contours called isodynamic charts. These charts reveal that the intensity of the earth’s magnetic field is highest at the poles, and decreases towards the equator. Thus, minimum intensties are experienced over areas like South America, while maximum intensities occur over the North American Arctic, Siberia and Greenland, as well as Antarctica.
Inclination. The inclination measures magnetic dip and assumes valued between -900 (up) and +900 (down). In the northern hemisphere, the magnetic dip or inclination points downwards, eventually becoming straight up and down at the magnetic north pole. If we move south, the inclination decreases with latitude until it reaches 00 at the equator. It then continues to rotate upwards until it reaches the south pole where it is straight up. Inclination was measured at Fort Conger using an instrument called a dip circle.
Declination. Declination refers to the difference between the magnetic north pole and the geographic pole, thereby representing an eastward deviation of the the field relative to true north.
Click on the Options button and select Play! You now have a more sophisticated device at your disposal – one that measures Intensity (left) and Inclination (right). A display located at the bottom of the screen shows you the magnetic pole/year you are seeking, the number of poles you have found, and the distance to the current pole. Use your mouse to move the instrument over the map. Pay attention to the distance value, which will decrease as you get closer to the pole. The Intensity and Inclination values should also increase as you approach your target.
Each time you play, the position of the pole randomly changes as a function of time. Successfully locate the pole five times, and then connect the pole locations to trace its route of migration.