Every 300,000 years the Earth’s magnetic poles switch places and we’re overdue a change! So just what causes this to happen…
A geomagnetic reversal is a change in the orientation of Earth’s magnetic field where magnetic north and south become interchanged. This occurs as Earth’s magnetic field derives from the fluid motion in its outer-core, with heat from the inner-core causing this ‘fluid’ to rise. It is the currents that flow in this electrically conductive iron-rich fluid that generate the magnetic field, so when these change, so does the field’s direction.
On average, every 300,000years Earth’s magnetic poles switch places; a process historically described and dated by the orientation of magnetite crystals set in place by cooling volcanic rocks. It is thought, though, that every few thousand years or so the fluid outer-core attempts to reverse, but that the solid inner-core can only change by diffusion and, because of this, actsasa braking mechanism. When it does actually occur, lengthy falls in field intensity tend to precede a reversal.
Interestingly, while current field strength is relatively high, it has continued to fall for approximately the past 2,000 years.