Answer:
Magnetic Reversals/ Flips
Step-by-step explanation:
Magnetic Reversals/ Flips are a shift in the magnetic field of the Earth resulting in alignment of the magnetic north with the geographic south and alignment of the magnetic south with the geographic north.
The Earth's magnetic field has experienced several polarity reversals as a matter of geological record. In average, there have been 4 to 5 reversals every million years over the past 10 million years.
Many times in the history of Earth, for example during the Cretaceous period, when there were no reversals, there were much longer periods. By fact, reversals are not linear and definitely are not periodic. Therefore, only the average reversal time can be spoken about.