Skip to main content Accessibility help
×
Home

Some archaeomagnetic results from Greece

  • J. C. Belshé, K. Cook and R. M. Cook

Extract

Many clays and stones contain particles of magnetic oxides of iron. These particles, if heated above their Curie points, which range up to 670° C., lose whatever magnetism they have; and when they cool back through their Curie points, they acquire a new ‘thermoremanent’ magnetization under the influence of the surrounding magnetic field, which generally is the magnetic field of the earth. That field is changing continuously, both in direction and intensity, and the course of its secular change is not yet understood; the change is compound, one factor being the main field, which may be fairly stationary over long periods, and the other being the numerous minor regional fields, which move and alter relatively quickly and largely determine the local variations in the magnetic field. So it is dangerous to extrapolate values for local variations either for more than a century or two in time or for more than five to ten degrees in space. At present the best hope for discovering past changes in the earth's field is from the thermoremanent magnetization of burnt clays and stones, where the date of the burning is reasonably closely fixed from other evidence. Such knowledge is obviously of interest to geophysicists, but for periods and places where the past course of the earth's field has been ascertained, archaeomagnetism—that is the study of the thermoremanent magnetization of archaeological remains—can help archaeologists too. It should be evident on reflection that if an archaeomagnetic specimen is to be useful certain requirements are necessary. First, the locality where it was magnetized must be known. Secondly, for the study of direction, the sample's orientation at the time when it was magnetized must be recorded, so that the inclination [or dip] and declination [or compass bearing] of its own thermoremanent magnetism can be related to the horizontal and to true North respectively.

Copyright

References

Hide All

1 For more details see Aitken, M. J., Physics and Archaeology, 811, 18–19, 121–55.Cook, R. M. and Belshé, J. C., Antiquity 1958, 167–78; Cook, R. M. in Brothwell, D. R. and Higgs, E. S., Science in Archaeology, 5971.

2 Conversely, if the date of magnetization is known, it might be possible to suggest the locality. A conceivable application, if there should prove to have been significant differences in the intensity between the relevant places, would be to decide whether certain pots had been made in Asia Minor or Egypt or Etruria.

3 Ancient Greek kilns seem to have been fired normally to temperatures of 900–950° C., that is, well above the Curie points of their components. Further, the practice of sinking the fire chamber in the ground gave that part of the kiln an unusually good chance of survival.

4 Fisher, Ronald, Proc. Royal Soc. A. ccxvii. 295305.

5 See the works quoted in n. 1.

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed