A multidisciplinary effort to reduce hazard from volcanic ash during Etna explosive eruptions

Volcanic ash is one of the major hazards produced during explosive eruptions. Fine volcanic ash is dispersed in atmosphere and causes disruptions to aviation, whilst tephra fallout affects infrastructure and vegetation causing economic losses. Etna is one of the most active volcanoes in the world and is considered among volcanoes that frequently cause damage to airport operations. The recent explosive activity produced powerful lava fountains with eruption columns rising several kilometres above the crater rim that formed copious tephra fallout on the east flanks. In order to reduce the hazard and help the civil protection to make right decisions, a reliable quantification of the eruptive phenomena is a necessary task. Since 2006, the INGV has improved the capability of providing accurate and fast information on the evolution of volcanic plumes during explosive eruptions of Etna. Monitoring is based on satellite images, visual and thermal cameras and radar disdrometers. Forecasting is performed using automatic procedures such as running models of tephra dispersal, plotting hazard maps of volcanic ash dispersal and deposition and publishing the results on a web-site dedicated to the Italian Civil Protection. A recent research project in collaboration with INAF-OACt, the Univ. Naples and the Univ. Malta, has furthermore improved the capability to observe volcanic plumes and extend the forecasting region. As an example, an innovative lidar system realized by CNISM allows estimation of the location of volcanic plumes in atmosphere and of important features such as column height and volcanic ash concentration. Other instruments installed in Malta are able to measure the distal part of the plume giving important constraint on the long-range path of volcanic plume. Statistical approaches applied to volcanic ash dispersal models have clearly shown that the mass eruption rate, the column height and the total grain- size distribution have a first order effect on the model results. All of the mentioned instruments will contribute towards the evaluation of the main eruption parameters and their uncertainties. Furthermore, we will show how the use of laboratory experiments gives a valuable help to understand physical processes occurring during the fallout from volcanic plumes. An example of how this system works is also presented. The next challenge should be the implementation of the capability to measure these parameters during an eruption and incorporate them into the model.