“... since the Second World War ... the proton magnetometer has revolutionized measurements, satellites have given new impetus to magnetic surveying, discoveries of large mineral deposits have maintained activity in conventional magnetic prospecting, and geomagnetism has continued to play a central role in major scientific developments such as plate tectonics (where the time scale of reversals of the polarity of the Earth's magnetic field still provides the main source of information on the movement of the plates.)”