The Earth’s magnetic field is, admittedly, pretty weak. A mere 50microtesla, it is quite inadequate, byitself, to make a lasting impression onrocks or sediments; natural magneticrecording is made possible only throughthe conspiracy of thermal, chemical, orphysical processes. Of course, it is thisvery weakness that makes possible thepreservation of paleomagnetic records ingeological materials - if the field weretoo potent, it would continuously resetall previously imprinted magnetizations.However, our purpose here is not somuch to praise the subtlety of thegeomagnetic field, as to explore theopposite end of the “power” spectrum:how strong can magnetic fields be? Certainly the field is greater in the Earth’s core than at the surface. The Mike Jackson IRM poloidal component reaches at least 100microtesla at the poles of the outer core(the poloidal component is the portion ofthe field oriented radially and/or north-south; this is the component we canmeasure at the surface) .