palaeomagnetism

/P AH0 L EY1 OW0 M AE1 G N AH0 T IH0 Z AH0 M/
noun
  1. 1

    The study of the strength and direction of the Earth's magnetic field as it has changed over geologic time.

Source: https://en.wiktionary.org/wiki/palaeomagnetism, https://en.wiktionary.org/wiki/paleomagnetism