Archaeomagnetic dating english heritage
When any material containing magnetic grains is heated above some 700 °C, it loses any previous remanent magnetisation.
The network comprises 12 laboratories across Europe including the UK, Austria, Belgium, Bulgaria, Denmark, France, Greece, Spain and Italy.Consequently older dates depend on having available archaeomagnetic directional and intensity records from previous studies of well-dated archaeological sites.Understandably, archaeologists usually request magnetic dating for sites that cannot be adequately dated by other means!This remanence also has an intensity of magnetisation that is proportional to the strength of the magnetic field at that time.
As the Earth’s magnetic field gradually changes both, direction and intensity, the direction and intensity of samples from the site can be dated by comparison with known direction and field intensity records for past times at that locality.
This is because the Earth’s magnetic field is fairly uniform (and therefore predictable) over an area of some 1 000 000 km region. burnt destruction levels several hundred km apart, that were fired at the same time will have identical directions and ancient field intensities.