Mount Etna: monitoring in the past, present and future

Mount Etna is important to the economy of eastern Sicily, with agriculture and summer and winter tourism providing employment for thousands of people. Although there are no permanent homes within 10 km of the summit, year-round human activities on the upper slopes are proliferating and the risks from even a small eruption are consequently magnified. The earliest form of monitoring at Etna, as for other volcanoes, was direct observation. Modern volcano monitoring at its most effective is a synergy between basic science and hazard assessment. A prerequisite to effective monitoring is an understanding of volcanic structure and history. Sir Charles Lyell was among the first to make systematic observations of Mount Etna and laid the foundation of more modern studies. A huge array of monitoring techniques has been tested on Etna; methods that have proved successful in monitoring and sometimes in predicting eruptions include observations of seismicity, ground deformation and microgravity. These, together with electromagnetic, magnetic, gas geochemistry and various remote sensing techniques have also provided key information on the volcanic plumbing system and the eruption process. Monitoring techniques were formerly based on the most easily measured phenomena; other effects were either not recorded or were treated as noise. Future progress will be enhanced by taking account of these more subtle or complex effects and by the more comprehensive acquisition and real-time analysis of continuous data sets over extended periods. Important monitoring techniques and strategies available both now and in the near future are reviewed here in the context of Etna. The need to develop a reliable scientific platform for routine and inexpensive volcano monitoring throughout the world is highlighted.