The magnetic field also gets very weak (90% drop in intensity and the magnetic pole way down near the equator) quite often. These are call magnetic excursions.

The magnetic field also gets very weak (90% drop in intensity and the magnetic pole way down near the equator) quite often. These are call magnetic excursions. They happen at an average frequency of maybe 50 thousand years or so with a high variance. The last big one is called the Las Champ excursion and happened about 41 thousand year ago. Species that needed a strong magnetic field that points north or south to exist would have gone extinct long ago. These species must have ways to survive when the Earth's magnetic field is unstable and weak because that happens on timescales much shorter than species evolution. [1]https://en.wikipedia.org/wiki/Laschamp_event https://en.wikipedia.org/wiki/Laschamp_event