Geomagnetic Field Flip-flops In A Flash - Science News: "Magnetic minerals in 15-million-year-old rocks appear to preserve a moment when the magnetic north pole was rapidly on its way to becoming the south pole, and vice versa. Such “geomagnetic field reversals” occur every couple hundred thousand years, normally taking about 4,000 years to make the change. The Nevada rocks suggest that this particular switch happened at a remarkably fast clip.
Anyone carrying a compass would have seen its measurements skew by about a degree a week — a flash in geologic time."
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