archaeomagnetism The non-destructive study of the magnetic properties of objects and materials from archaeological sites. Such studies include magnetic dating, reconstruction of objects and structures, sourcing artefacts, determining past firing temperatures, etc. Artefacts often cause a local slight distortion of the Earth's magnetic field, which can be detected by a magnetometer. Materials that have been raised to a high temperature (fired pottery, kilns, etc.) can be dated by their thermoremanent magnetism (TRM). When substances containing iron and nickel compounds are heated strongly, the metals become randomly oriented with respect to the Earth's magnetic field, but as they cool below their Curie temperature (760°C for iron, 365°C for nickel) they become oriented with the magnetic field. Dating is achieved by comparing their magnetic orientation with the Earth's present magnetic field and relating this to a master sequence of changes caused by the wandering of the magnetic North Pole.

archaeomagnetism The study of the magnetic properties of objects and materials from an archaeological context. Such studies include magnetic dating, reconstruction of objects and structures, sourcing artefacts, past firing temperatures, etc.