City of pompeii isotopic dating

If there has been significant change in the temperature during the time in which the object is buried, the result is flawed.

Other problems of contamination have occurred, so the technique is not fully established.

It is fairly reliable for deep-sea sediments as the temperature is generally more stable.

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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.

Therefore, pottery which is baked in effect fossilizes" the Earth's magnetic field as it was the moment of their last cooling (their archaeomagnetism or remanent magnetism).

SYNONYMS OR RELATED TERMS: chronometric dating; absolute dates; absolute chronology; absolute age determination (antonym: relative dating)CATEGORY: chronology; technique DEFINITION: The determination of age with reference to a specific time scale, such as a fixed calendrical system or in years before present (B.

P., BP), based on measurable physical and chemical qualities or historical associations such as coins and written records.

The date on a coin is an absolute date, as are AD 1492 or 501 SYNONYMS OR RELATED TERMS: amino-acid dating; aminostratigraphy; amino-acid racemization, amino acid racemization CATEGORY: technique DEFINITION: A method of absolute (chronometric) dating which is hoped to fill the gap between radiocarbon dates and potassium-argon dates.

It is used for human and animal bone and other organic material.

Specific changes in its amino acid structure (racemization or epimerization) which occur at a slow, relatively uniform rate, are measured after the organism's death.

The basis for the technique is the fact that almost all amino acids change from optically active to optically passive compounds (racemize) over a period of time.

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