Cathy Constable reconstructs global maps of the Earth’s magnetic field over timescales from millennia to millions of years using the remnant magnetism “frozen” into human artifacts and rocks.  This has revealed surprising patterns of variation that in turn cast light on the processes in the Earth’s core that are responsible for generating the field.

Cathy Constable is a Professor at the Scripps Institution of Oceanography. 

Go to geologybites.com to see an animation of the global magnetic field patterns around the time of the last major excursion about 40,000 years ago when the Earth's magnetic field almost vanished entirely.