[cripplecreek]

Reversals in the Earth’s magnetic field means, the magnetic poles of the Earth have shifted in short amounts of time, and many more times than once or twice; and the shifts (which are recorded in ferrous rocks that used to be molten lava) are not related to continental drift.

Something like every 300,000 years.

[Melas]

No time scale. There is evidence of intervals as short as 50,000 years, with others as long as 10 million years. Seemingly random.