Earth magnetic polarity reversal

The Earth's magnetic polarity field may be reversing.

Earth's magnetic field has been weakening demonstrably since Gauss's first measurement in 1845. That weakening is a signal of impending reversal, in modern theory.

Relatively non-catastrophic, the planetary magnetic flip is normal but aperiodic and unpredictable. It has not happened within the age of biologically modern humans and so its potential effects are unknown. Prediction of its recurrence is not yet possible.

The geological evidence of polarity reversal is not visible without instrumentation, but with instrumentation that evidence is not only visible but legible. The iron particles within cooling magma record the polarity of the magnetic field at a moment. This is important in the study of geological plate tectonics, providing a time-stamp against which science can extrapolate continental movements, dating lava flows based upon comparison with the known magnetic polarity of the era.

The most recent polarity reversal was about 780,000 years ago. The record shows that a "chron" varies in duration between tens of thousands of years and tens of millions.

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