kääntöpoikkeama

Kääntöpoikkeama, a Finnish term, translates to "turning deviation" or "reversal anomaly" and refers to a phenomenon in astronomy and geophysics. It describes a situation where the Earth's magnetic field undergoes a significant and relatively rapid change in its polarity, meaning the north and south magnetic poles swap places. This is not a single, instantaneous event but rather a process that can take thousands of years to complete. During the transition, the magnetic field weakens considerably, and multiple temporary poles might emerge.

The Earth's magnetic field is generated by the movement of molten iron in the planet's outer core. This dynamo process is complex and subject to fluctuations. Kääntöpoikkeama is believed to be a natural part of the geodynamo's behavior, occurring at irregular intervals throughout geological history. Evidence for these reversals is found in the magnetic record preserved in rocks, particularly volcanic rocks that record the prevailing magnetic field at the time of their formation.

The last full reversal, known as the Brunhes–Matuyama reversal, occurred approximately 780,000 years ago. While the Earth's magnetic field is currently weakening and its north magnetic pole is drifting, it is unclear whether this indicates the onset of a new kääntöpoikkeama. Scientists study these reversals to understand the Earth's internal dynamics, as well as to assess potential impacts on technology and life due to a weaker magnetic field during a transitional period.