Natural remanent magnetization
- Natural remanent magnetization
-
Natural remanent magnetization (NRM) is the permanent magnetism of a rock or sediment. In some forms, it can preserve a record of the Earth's field and the tectonic movement of the rock over millions of years. Natural remanent magnetization forms the basis of paleomagnetism and magnetostratigraphy.
Types of natural remanent magnetization
There are several kinds of NRM that can occur in a sample. Many samples have more than one kind superimposed. 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 depositional remanent magnetization during their formation or a post-depositional remanent magnetization afterwards.[1]
Some kinds of remanence are undesirable and must be removed before the useful remanence is measured. One is isothermal remanent magnetization (IRM), which as a component of NRM generally means remanence induced by lightning strikes. Another is viscous remanent magnetization (VRM), a remanence acquired when the rock sits in the Earth's field for long periods.[1]
The most important component of remanence is that acquired when a rock formed. This is called its primary component or characteristic remanent magnetization (ChRM). Any later component is called a secondary component. To separate these components, the NRM is stripped away in a stepwise manner using thermal or alternating field demagnetization techniques to reveal the stable magnetic component.[1]
See also
Notes
References
- Dunlop, David J.; Özdemir, Özden (1997). Rock Magnetism: Fundamentals and Frontiers. Cambridge Univ. Press. ISBN 0-521-32514-5.
- Nichols, Gary (1999). Sedimentology & Stratigraphy (1st ed.). Wiley-Blackwell. ISBN 978-0632035786.
- McElhinny, Michael W.; McFadden, Phillip L. (2000). Paleomagnetism: Continents and Oceans. Academic Press. ISBN 0124833551.
Categories:
- Magnetic ordering
- Stratigraphy
- Geochronology stubs
- Geophysics stubs
Wikimedia Foundation.
2010.
Look at other dictionaries:
Natural Remanent Magnetization — (Abbreviated NRM) is the permanent magnetism of a rock. The NRM is frozen into the rock. It does not change with other location.The NRM is stripped away in a stepwise manner using thermal or alternating field demagnetization techniques to reveal… … Wikipedia
remanent magnetism — Geol. magnetization in minerals induced by a former magnetic field and persisting after the field changes. Cf. paleomagnetism. [1865 70] * * * ▪ rocks also called Paleomagnetism, or Palaeomagnetism, the permanent magnetism in rocks,… … Universalium
paleomagnetism — Natural remanent magnetization preserved in rock sequences. During rock deposition magnetic minerals are aligned according to the direction and polarity of the earth’s contemporary magnetic field. After movement of the magnetic poles, or… … Lexicon of Cave and Karst Terminology
rock — rock1 rockless, adj. rocklike, adj. /rok/, n. 1. a large mass of stone forming a hill, cliff, promontory, or the like. 2. Geol. a. mineral matter of variable composition, consolidated or unconsolidated, assembled in masses or considerable… … Universalium
Rock — /rok/, n. a male given name. * * * I In geology, a naturally occurring and coherent aggregate of minerals. The three major classes of rock igneous, sedimentary, and metamorphic are based on the processes that formed them. These three classes are… … Universalium
Magnetostratigraphy — is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their characteristic… … Wikipedia
Outline of geophysics — Seismic velocities and boundaries in the interior of the Earth sampled by seismic waves. The following outline is provided as an overview of and topical guide to geophysics: Geophysics – the physics of the Earth and its environment in space; also … Wikipedia
Stratigraphy — Stratigraphy, a branch of geology, studies rock layers and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy includes two related subfields: lithologic or lithostratigraphy and… … Wikipedia
mining — /muy ning/, n. 1. the act, process, or industry of extracting ores, coal, etc., from mines. 2. the laying of explosive mines. [1250 1300; ME: undermining (walls in an attack); see MINE2, ING1] * * * I Excavation of materials from the Earth s… … Universalium
NRM — is a three letter acronym that can refer to: National Railway Museum, York, UK National Railway Museum (disambiguation) in general National Resistance Movement, a political organisation in Uganda Natural remanent magnetization, used in… … Wikipedia
