Paleomagnetism

Definition

Paleomagnetism is the record of the Earth’s past magnetic field preserved in rocks. The orientation of the magnetic field, retained in ferromagnetic minerals (Fe-Ti oxides and sulfides), mirrors the Earth’s magnetic field at the time the minerals passed through their Curie point (i.e., the temperature at which certain magnetic materials undergo a sharp change in their magnetic properties). By measuring the orientation (inclination and declination) and the intensity of this magnetism, it is possible to establish the paleo-latitude of the sample at the time of its cooling or recrystallization. Apparent polar wander curves determined using such data record the displacement of continents and provide evidence of past plate tectonics. Variations in intensity of the remnant field record changes in the strength of the Earth’s magnetic field and the start of crystallization of the inner core. Paleomagnetism has also been measured on Marsand shown that natural remnant magnetism is...