Direct observations of the present Earth’s magnetic field only go back for some 400 years (can be done using either the direction or the intensity of magnetisation (or better both) of burnt materials.
When these were originally heated in antiquity, they acquired a direction of magnetisation (magnetic remanence) in the same direction as the Earth’s magnetic field (also called geomagnetic field) at that site at that time.
Changes of the field strength can influence the life on Earth and may act as evolutional sieve.
The Earth's magnetic field is a huge shield, protecting us against the bombardment of high energy particles.
Archaeological materials provide an irreplaceable record of the direction and intensity of the Earth's magnetic field in the past, using archaeomagnetic studies.
At present, such records within Europe are irregular in both space and time.
Fortunately, such well-dated sites can come from a wide region – within some 600 km of the site being investigated. However, there is an interest to extend the record of the geomagnetic field into the past and to combine the results with theoretical reversal models. Nowadays, the detailed mechanism of the magnetic field is still not yet completely clear, in particular the reversal process when the strength of the geomagnetic field is considerably reduced. Archaeological material, however, does not have such implications and records the magnetic field more confidently, as the field recording process is different. Lake, marine and continental sediments are often not reliable for an accurate registration of the geomagnetic field, because of delayed recording due to complex sedimentation environment and magnetic mineralogy.