Rock magnetism

Rock magnetism studies magnetic minerals and magnetic properties in rocks, including how rocks acquire and preserve records of Earth’s magnetic field.

Connect

Natural remanent magnetization: Magnetization retained by a rock after the external field that induced it has changed or disappeared. This is the stored magnetic signal rock-magnetic methods measure and interpret.
Magnetite: An iron oxide mineral that is ferrimagnetic at ordinary surface temperatures. Its abundance and strong magnetic response make it a major carrier of rock magnetization.
Paleomagnetism: The study of the record of Earth’s magnetic field preserved in rocks and sediments. It uses remanence and mineral tests to reconstruct past field directions and changes.
Induced magnetization: Magnetization produced in a material by an applied magnetic field and usually lost when the field is removed. It differs from the persistent remanence used to recover ancient field records.
Thermoremanent magnetization: A remanent magnetization acquired as magnetic minerals cool through their Curie or blocking temperatures in a magnetic field. Cooling lava can lock in the direction and strength of the contemporary field.
Hematite: An iron oxide mineral that is weakly ferromagnetic at ordinary temperatures. It can preserve stable remanence, sometimes through geological timescales.
Magnetostratigraphy: A method of correlating and dating rock sequences using recorded changes in magnetic polarity. Magnetic mineral records identify polarity intervals in sedimentary and volcanic sequences.
Isothermal remanent magnetization: A remanent magnetization acquired at constant temperature through exposure to a magnetic field. Laboratory IRM experiments probe coercivity and help identify magnetic components.
Chemical remanent magnetization: Magnetization acquired as magnetic minerals form or grow in an external magnetic field. Mineral alteration can create magnetic records long after a rock formed.
Maghemite: A ferrimagnetic iron oxide mineral commonly formed by oxidation of magnetite. Its formation can change a rock’s magnetic properties and remanent signal.