Video: Earth's wandering magnetic fieldNovember 26, 2013 in Earth / Earth Sciences
Earth's magnetic field is continuously changing.
Magnetic north wanders, and every few hundred thousand years the polarity gradually flips, so that a compass would point south instead of north.
Provided by European Space Agency
"Video: Earth's wandering magnetic field" November 26, 2013 http://phys.org/news/2013-11-video-earth-magnetic-field_1.html