But even as their databases grew, the study of geomagnetic reversals
foundered for lack of new theories to guide the research.
There is evidence, although some call it statistically marginal, that the rate of geomagnetic reversals
peaked during the mass extinctions.
But the actual frequency of geomagnetic reversals
can vary considerably.
A relatively stronger present-day field helps explain why Earth hasn't had a geomagnetic reversal
for 780,000 years, says geophysicist Peter Driscoll of the Carnegie Institution for Science in Washington, D.