Geographic north is a fixed point on Earth’s surface where the planet’s rotational axis meets the top of the globe. Magnetic north is the point your compass needle actually points toward, and it sits in a different location that shifts constantly. As of 2025, the two poles are roughly 1,200 miles apart, which means every compass reading contains a built-in error unless you account for the gap.
Why There Are Two “Norths”
Geographic north, also called true north, is determined by Earth’s spin. The planet rotates around an axis, and the spot where that axis intersects the surface in the Arctic is the Geographic North Pole. It doesn’t move in any meaningful way. Maps, GPS systems, and lines of longitude are all oriented toward this point.
Magnetic north exists because Earth generates its own magnetic field. Deep below the surface, the outer core is a churning ocean of liquid iron. Radioactive heating and chemical processes drive this molten metal into turbulent, convective motion. Because the iron conducts electricity, its movement through the existing magnetic field generates electric currents, which in turn produce more magnetic field. This self-sustaining loop, sometimes called a geodynamo, is what makes the entire planet act like a giant magnet. The spot on Earth’s surface where a compass needle dips straight down toward the core is the magnetic north pole, and it currently sits at about 85.8°N, 139.3°E, in the Arctic Ocean north of Siberia.
Why Magnetic North Keeps Moving
Because the geodynamo depends on fluid motion rather than a fixed structure, the magnetic pole wanders. For most of the 20th century, it drifted at a leisurely pace of about 9 miles (15 km) per year. Since the 1990s, that drift has accelerated dramatically. The magnetic north pole now moves roughly 30 to 40 miles (50 to 60 km) per year, heading from the Canadian Arctic toward Siberia.
Scientists attribute the speedup to changes in the flow patterns of molten iron deep beneath the surface. These shifts in the core also mean the magnetic field’s overall strength and shape aren’t uniform. In some regions, compass needles are pulled slightly east of true north; in others, slightly west. The angle of that offset is different depending on where you stand on the planet.
Magnetic Declination: Measuring the Gap
The angle between true north and magnetic north at any given location is called magnetic declination (sometimes called magnetic variation). If your compass needle points east of true north, declination is positive. If it points west, declination is negative. In some parts of the United States, declination is close to zero, while in others it can be 15 degrees or more.
To convert a compass reading to a true bearing, you add the local declination value, treating westward declination as a negative number. So if your compass says you’re facing 90 degrees (due east) and your local declination is 10 degrees west, the true bearing is 90 + (−10) = 80 degrees. Getting this wrong over a long hike or a cross-country flight compounds quickly: one degree of error translates to roughly a mile of drift for every 60 miles traveled.
Adjusting a Compass in the Field
Many baseplate compasses have a built-in adjustment for declination. You rotate the inner capsule, or turn a small screw with a key, until the orienting arrow is offset from the north marking by the amount and direction of your local declination. If local declination is 10 degrees east, for example, you set the orienting arrow to point at 10 degrees east on the dial. Once set, the compass effectively converts magnetic bearings to true bearings automatically, so your map and your compass agree without mental math on every reading.
You can look up your local declination through NOAA’s National Centers for Environmental Information, which publishes an online calculator. The value changes over time, so if you’re using a topographic map printed years ago, the declination printed in the map margin may no longer be accurate.
How Shifting Poles Affect Aviation
Airport runways are one of the most visible places where the difference between geographic and magnetic north shows up in everyday life. Under FAA rules, runways are numbered based on their magnetic compass heading, rounded to the nearest 10 degrees with the last digit dropped. A runway aligned to a magnetic heading of 170 degrees is called Runway 17.
As the magnetic field shifts, those headings drift, and eventually the numbers have to change. Fairbanks International Airport in Alaska renamed runway 1L-19R to 2L-20R in 2009, and airport officials expect another update around 2033. Denver International Airport has a runway currently oriented at 172.5 degrees magnetic; when the field shifts another 4 degrees, that runway will be renamed from 17L-35R to 18L-36R. Airports closer to the poles feel these shifts more quickly because the magnetic field changes faster at high latitudes. Fairbanks, for instance, updates roughly every 24 years.
The aviation industry relies on the World Magnetic Model (WMM) to keep all of this current. The latest version, WMM2025, was released in December 2024 and will remain valid until late 2029. A new version comes out every five years. The FAA requires navigation aids to stay within 1 degree of the current computed magnetic variation, so the WMM feeds directly into instrument landing systems, air traffic control procedures, and runway designations worldwide.
Full Reversals of the Magnetic Field
The magnetic poles don’t just wander. Over geological time, they swap entirely. Earth’s magnetic field has flipped hundreds of times, with the north and south magnetic poles essentially trading places. These reversals are unpredictable. They’ve happened as frequently as every 10,000 years and as rarely as once every 50 million years. The last full reversal occurred about 780,000 years ago.
A reversal wouldn’t move the geographic poles at all, since those are defined by the planet’s rotation. But during the transition, which can take thousands of years, the magnetic field weakens and becomes more complex, with multiple magnetic poles appearing at odd latitudes. Compass navigation would become unreliable in that scenario, though GPS and other satellite-based systems rely on true north and would be unaffected.
A Technical Detail: Two Kinds of Magnetic Pole
Scientists actually track two slightly different versions of the magnetic north pole. The “magnetic dip pole” is the physical spot where a compass needle tilts straight downward, currently at 85.8°N. The “geomagnetic north pole” is a theoretical point based on modeling Earth’s field as a simple bar magnet tilted inside the planet; that point sits at about 80.9°N, 72.8°W, closer to Greenland. For everyday navigation, the dip pole is what matters, because that’s where your compass actually points. The geomagnetic pole is more useful for studying space weather and the behavior of charged particles entering Earth’s atmosphere.