Geomagnetic reversal
Also called: Magnetic pole reversal · Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Beyond NCERT
Meaning
A geomagnetic reversal is when the earth's magnetic north and south poles swap places. The magnetic field comes from liquid iron moving in the outer core, and this flow can change direction over time. Reversals have happened hundreds of times. The last full one, the Brunhes-Matuyama reversal, was about 780,000 years ago. When lava cools at mid-ocean ridges, its iron minerals line up with the field of that time. This leaves "magnetic stripes" on the ocean floor, which are key evidence for sea-floor spreading.
Example
The Carlsberg Ridge in the Arabian Sea, south-west of India, shows matching bands of normal and reversed magnetism on both sides of the ridge. This was one of the early proofs of sea-floor spreading.
Don't confuse with
- Drift of the magnetic north pole: the pole is slowly moving from the Canadian Arctic towards Siberia. That is a shift in position, not a swap of the north and south poles.