Magnetic Pole

Magnetic Pole, either of two points on the surface of the Earth, to which one end of a compass needle is attracted and from which the other end is repelled.

The magnetic poles are located at considerable distances from the geographical poles, at the northern and southern ends of the magnetic field, at the polar areas of the northern hemisphere and southern hemisphere. The north magnetic pole is currently situated (1997) to the west of Ellef Ringnes Island in the Queen Elizabeth Islands of northern Canada, about 1,300 km (800 mi) from the North Pole. The south magnetic pole is currently situated in the Southern Ocean near the Adélie Coast of Antarctica, about 2,600 km (1,600 mi) from the South Pole. The magnetic field at these poles is vertical. Most maps indicate the directions of both true north, meaning the direction of the geographic north pole, and magnetic north, the direction in which a compass points. The difference in angle between the direction of true north and magnetic north at any given point on a map is known as the declination. Knowledge of magnetic declination is critically important when navigating with a compass and a map.

Scientists sometimes find it easier to model the earth’s magnetic field as if it were a perfectly symmetrical magnetic field coming from one large bar magnet. The poles of this hypothetical magnetic field, based on averaging the direction and strength of earth’s magnetic field, are called the geomagnetic poles. The north geomagnetic pole is located near Thule, Greenland, 1,250 km (780 miles) from the geographical North Pole. The south geomagnetic pole is located near Vostok, Antarctica, 1,250 km (780 miles) from the geographic South Pole.

The magnetic poles change location with time, a phenomenon known as polar wandering, and the direction of wandering has been observed to reverse. During geological history the polarity of the Earth's magnetic field has periodically reversed. It is a gradual process, taking between one and five thousand years to complete, and happens roughly every 500,000 years.