The presence of buried archaeological features, underground steel tanks or drums, and other ferrous buried objects can often be detected by a magnetometer survey, which detects small anomalies in the earth’s magnetic field that exist between buried structures and the surrounding substrate or bedrock. This effect is principally due to the varying iron content in the soil and rock forming minerals. Certain features, notably fired clay structures (such as kilns, hearths and furnaces), acquire their own magnetic identity, which is discernible and different from the other geomagnetic activity in the area.
Magnetometers are also used in a broader prospecting role to initially locate areas of ‘magnetic activity’ and also to help determine the extent of anomalies associated with previously identified features.
