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Magnetic Attraction

WHOI geologist Maurice Tivey has an unusual speciality: He studies the magnetic properties of rocks. When volcanic magma solidifies, magnetic crystals form in rocks and become oriented in the direction of Earth’s prevailing magnetic field. Over the planet’s 4.5-billion-year history, this field has flip-flopped many times, with magnetic north and south reversing direction. These reversals are well-documented and so, by analyzing rocks’ magnetic properties, Tivey can date them and chronicle the geological processes in which they formed. He has used deep-sea vehicles to study seafloor crust and recently took part in an expedition to drill to the Moho, the boundary between Earth’s mantle and crust.(Photo courtesy of Maurice Tivey, Woods Hole Oceanographic Institution)