What are reversals?

Answer 1

In the past, the polarity of the Earth's magnetic field has reversed, many times over. This was discovered in samples of the rocks of the ocean floor at mid-ocean ridges, where matching patterns of magnetic polarity were discovered on each side of the mid ocean ridge.

It is believed that the magnetic field is caused by electrical currents in the Earth's interior. [We know that the interior is too hot to sustain the magnetism of a bar magnet. As proved by the Curie's.]

If these currents circulate parallel to the equator, then they would be pretty stable. but we know that the poles are moving. This may indicate that the path of electrical conduction is not a simple circle. We just have to wait.

The earth's magnetic field is caused by the effect of the Earth's rotation on the liquid iron core. This field occasionally flips so that the direction that was magnetic north becomes magnetic south and what was magnetic south becomes magnetic north.

This is called a magnetic reversal and these reversals can be detected in Earth's lava rocks which lock in the direction of the current field when they cool and solidify.

Earth's magnetic field flips about once every 100 thousand years. The Sun goes through similar magnetic reversal cycles but on the Sun the reversals happen about once every 11 years.

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