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Thermoremanent magnetization. When an igneous rock cools, it acquires a thermoremanent magnetization (TRM) from the Earth's field. TRM can be much larger than it would be if exposed to the same field at room temperature (see isothermal remanence). This remanence can also be very stable, lasting without significant change for millions of years.
Thermoremanent magnetization is the main source of the magnetic anomalies around mid-ocean ridges. As the seafloor spreads, magma wells up from the mantle , cools to form new basaltic crust on both sides of the ridge, and is carried away from it by seafloor spreading.
TRM is the main reason that paleomagnetists are able to deduce the direction and magnitude of the ancient Earth's field. [7] If a rock is later re-heated (as a result of burial, for example), part or all of the TRM can be replaced by a new remanence. If it is only part of the remanence, it is known as partial thermoremanent magnetization (pTRM ...
Thermoremanent magnetization on Earth gives iron minerals formed in the Earth's crust, a higher magnetization than if they were formed in the same field at room temperature. This is a non-conventional thermoremanent magnetization because it appears to be due to a chemical remanent process which is induced as taenite is cooled to kamacite.
Thermoremanent magnetization (TRM) is acquired during cooling through the Curie temperature of the magnetic minerals and is the best source of information on the past Earth's field. Magnetization formed by phase change, chemical action or growth of crystals at low temperature is called chemical remanent magnetization. Sediments acquire a ...
The record so preserved is called a thermoremanent magnetization (TRM). Because complex oxidation reactions may occur as igneous rocks cool after crystallization, the orientations of Earth's magnetic field are not always accurately recorded, nor is the record necessarily maintained.
In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying material. The magnetic variation (geomagnetic reversals) in successive bands of ocean floor ...
Néel relaxation theory is a theory developed by Louis Néel in 1949 [1] to explain time-dependent magnetic phenomena known as magnetic viscosity [clarification needed].It is also called Néel-Arrhenius theory, after the Arrhenius equation, and Néel-Brown theory after a more rigorous derivation by William Fuller Brown, Jr. [2] Néel used his theory to develop a model of thermoremanent ...