THE SARGASSO SEA/BERMUDA TRIANGLE

Compass variations





Compass problems are one of the cited phrases in many Triangle incidents. The North Magnetic Pole is not the North Pole; rather it is the north end of the earth's magnetic field. The North Magnetic Pole does wander, but so slowly that the wandering would not be noticeable on time scale of a sea or air voyage.

In general, the compass does not point exactly the direction of the North Magnetic Pole, but rather the compass needle aligns itself to the local geomagnetic field, which can vary in a complex manner over the Earth's surface, as well as over time.

The angular difference between magnetic north and true north (defined in reference to the Geographic North Pole), at any particular location on the Earth's surface, is called the magnetic declination. Most map coordinate systems are based on true north, and magnetic declination is often shown on map legends so that the direction of true north can be determined from north as indicated by a compass.

The line of zero declination in the U.S. runs from the North Magnetic Pole through Lake Superior and across the western panhandle of Florida. Along this line, true north is the same as magnetic north. West of the line of zero declination, a compass will give a reading that is east of true north.

Conversely, east of the line of zero declination, a compass reading will be west of true north. Since the North Magnetic Pole has been slowly migrating toward the northwest, some twenty or more years ago the line of zero declination went through the Triangle, giving sailors an alignment of true north with magnetic north.

Some have theorized the possibility of unusual local magnetic anomalies in the area, however these have not been shown to exist.