Earth's last magnetic reversal took place 786,000 years ago and happened very quickly, in less than 100 years -- roughly a human lifetime. The rapid flip, much faster than the thousands of years most geologists thought, comes as new measurements show the planet's magnetic field is weakening 10 times faster than normal and could drop to zero in a few thousand years.Still, not in my lifetime. [Is that like "not in my backyard"?]
Though a magnetic reversal is a major planet-wide event driven by convection in Earth's iron core, there are no documented catastrophes associated with past reversals, despite much searching in the geologic and biologic record. Today, however, such a reversal could potentially wreak havoc with our electrical grid, generating currents that might take it down.