When magnetic north and true north align, it is called a *geomagnetic reversal*. This occurs when the north and south magnetic poles switch positions, and earth's magnetic field temporarily weakens to nearly zero. Magnetic reversals are irregular and the polarity changes occur thousands to millions of years apart, but occur somewhat frequently on geological time scales.

Scientists believe that reversals are caused by changes in the Earth's molten, outer core. The iron rich layer of the outer core is in constant, turbulent motion, and generates electric currents that create the Earth's magnetic field. Changes in these internal motions and fluid flow cause shifts in the magnetic field, leading to reversals.

When a geomagnetic reversal occurs, navigation instruments such as compasses point to the new magnetic north, and the Earth's magnetic field weakens dramatically. This field provides protection against harmful solar radiation and charged particles from the sun. During polarity switches, the field's strength reduces significantly.

Geomagnetic reversals have been linked to several phenomenon on the Earth, such as changes in the atmosphere, climate patterns, mass extinctions, and even shifts in the Earth's rotation axis. While the exact relationship is not fully understood, these events are believed to have a significant impact on Earth's system. Scientists study geomagnetic reversals to better understand the Earths, evolution, and how its interior dynamics influences the planet's habitable conditions.