Kilometer-scale heterogeneities inside volcanoes revealed by using a set of geophysical methods: variable stress field at Mount Etna, Sicily

A multidisciplinary study involving geological and geophysical techniques h as been carried out on the lower southern slope of Mt. Etna, with the aim o f discovering kilometer-scale heterogeneities, which are crucial in underst anding how the volcano works. In this area, faults and ancient eruptive fra ctures outcrop, with a NNW-SSE trend. together with volcanic structures, su ch as elongated hills, also trending NNW-SSE or E-W, which had never been e videnced in the Etna Literature. The old landscape has been revealed by con siderable erosion. Gravimetry and seismic tomography prospecting, added to geoelectric and drilling surveys, show that the morphology of the sedimenta ry substratum forms a N-S trending horst, limited to the east and west by d epressions, where erosion products and lava flows from the overlying volcan ic pile have accumulated. There is also evidence at very shallow depth (con gruent to 1 km below sea level) of an elongated body with a NNW-SSE directi on, which is interpreted as a small magma chamber that has now almost compl etely solidified. This shallow magma system is likely to have fed the 122 B C and congruent to 1150 AD eruptions, which historical accounts suggest are located very close to the city of Catania. (C) 2000 Elsevier Science B.V. All rights reserved.