Why Would Magnetic North Differ by Location?

Magnetic Field Movement and Changes

The Earth’s magnetic field is generated by the movement of molten iron in its liquid outer core, approximately 2,250 kilometers thick. This movement creates electric currents, which in turn generate the magnetic field. As the molten iron moves, it causes the magnetic field to shift and change over time, resulting in variations in the Earth’s magnetic field strength and direction.

Declination and Its Importance

Declination, also known as magnetic variation, is the difference between Magnetic North and True North. Declination varies by location and can change over time due to the shifting magnetic field. For example, in the 18th century, the declination in New York City was 16 degrees east, but by the 20th century, it had shifted to 13 degrees west. A navigation compass must be adjusted for declination to ensure accurate navigation, as an unadjusted compass can lead to errors of up to 20 miles in a single day.

Navigation and Declination Charts

To navigate accurately, it’s essential to use declination charts or online tools that provide the current declination for a specific location. These charts typically show the declination for a particular region, with the date range for which the declination is valid. By consulting these charts, navigators can adjust their compass for the correct declination and ensure accurate navigation. For instance, a navigator planning a trip in the northern United States in 2020 would need to adjust their compass for a declination of approximately 16 degrees west.