In addition to pedogenesis, thermodynamic state changes induced by fire contribute to transformations of iron minerals that in turn generate magnetic enhancement of the ground. Some of these new minerals are nanometric markers of fire-related practices that can be detect by magnetic methods, even in trace levels. The sensitivity of the tools available to measure the magnetic properties of materials, whether in situ or in the laboratory on samples, places magnetic methods among the favoured methods for detecting areas of past human occupation and for assessing the role of fire in these areas.