Define palaeomagnetism. How is palaeomagnetism preserved in the rocks? Add a note on geomagnetic time scale.
Palaeomagnetism is the study of the record of the Earth's magnetic field preserved in rocks, sediments, and archaeological materials. It is based on the principle that certain minerals within rocks can acquire and retain a remanent magnetization aligned with the Earth's magnetic field at the time of their formation. This preserved magnetization provides valuable insights into past geomagnetic field variations, plate tectonics, and the movement of continents over geological time.
Preservation of Palaeomagnetism in Rocks
The preservation of palaeomagnetism in rocks occurs through various mechanisms, primarily involving magnetic minerals such as magnetite (Fe₃O₄), hematite (Fe₂O₃), and goethite (FeO(OH)). The primary ways in which palaeomagnetism is recorded in rocks include:
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Thermoremanent Magnetization (TRM):
- Found in igneous rocks, particularly basalts.
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