Retrieval of large volcanomagnetic effects observed during the 1981 eruption of Mt.Etna

Abstract

A large temporal anomaly was retrieved in the total geomagnetic field series recorded in 1981 on Mt. Etna at two continuously recording magnetometers, and associated with the March 17-23 eruption of the volcano. Variations were of such large scale that a 10 nT anomaly was observed at a distance of some 7 km from the eruptive events, calling for a significant extension and depth of the magnetic anomaly source. We discuss here some models which may account for such magnetic changes in relation to the eruption mechanism inferred by other data. The anomaly is thought to be accounted for by the joint effect of piezomagnetism of the country rocks and thermal demagnetisation engendered by a large intrusive dyke.