Clay and rocks contain magnetic minerals and when heated above a certain temperature, the magnetism is destroyed.Upon cooling, the magnetism returns, taking on the direction and strength of the magnetic field in which the object is lying.dating technique relies on the progressive decay or disappearance of the radioactive parent with time.
Still, the most commonly used is SYNONYMS OR RELATED TERMS: radiocarbon dating CATEGORY: technique DEFINITION: The occurrence of natural radioactive carbon in the atmosphere allows archaeologists the ability to date organic materials as old as 50,000 years.The test is used mainly in association with the fluorine test and radiometric assay, as in the cases of Piltdown and Swanscombe Man. The basis of cross-dating is the occurrence of finds in association.The assumption is that a particular type of artifact, for example a type of sword, when found in an undated context will bear a similar date to one found in a dated context, thus enabling the whole of the undated context to be given a chronological value.However, its use is still helpful where recognizable products of dateable manufacture are found in undated contexts with no possibility of using a technique.So in the absence of geochronology, two cultural groups can only be proved contemporary by the discovery of links between them.
This method yields an absolute date within about 50 years."CATEGORY: technique DEFINITION: Any of a serious of methods of analyzing bone samples, especially by measuring fluorine, uranium, nitrogen -- also called the FUN technique -- or by using stratigraphy.