Earth Changes
2004 and Beyond

Anomalies hint at magnetic pole flip

19:00 10 April 02

The Earth's magnetic poles might be starting to flip say researchers who have seen strange anomalies in our planet's magnetic field.

The magnetic field is created by the flow of molten iron inside the Earth's core. These circulation patterns are affected by the planet's rotation, so the field normally aligns with the Earth's axis - forming the north and south poles.

But the way minerals are aligned in ancient rock shows that the planet's magnetic dipole occasionally disappears altogether, leaving a much more complicated field with many poles all over the planet. When the dipole comes back into force, the north and south poles can swap places.

The last reversal happened about 780,000 years ago, over a period of several thousand years. Now Gauthier Hulot from the Institute of Earth Sciences in Paris and his colleagues think they have spotted early signs of another reversal.

South African anomaly

They used data from the Ørsted satellite to study strange variations in the Earth's magnetic field. In particular, one large patch under South Africa is pointing in the opposite direction from the rest of the Earth's field and has been growing for hundreds of years.

The anomalies have already reduced the overall strength of the planet's magnetic field by about 10 per cent. If they continue to grow at the same rate, the Earth's dipole will disappear within just two millennia.

But Ørsted is the first satellite to take a snapshot of the Earth's magnetic field for 20 years, and such scant data makes it difficult to predict future shifts.

"We can't really tell what will happen," says Hulot. "But we speculate that we're in an unusual situation that might be related to a reversal."

Fotenote: The Earth's magnetic field is showing worrying signs that it is about to reverse again. The magnetic north pole has wandered by 1100 kilometres in the past 200 years and its (magnetic field) strength is dropping at a rate of 5 per cent a century.

This is the fastest decrease since the last reversal 730,000 years ago.