ORIGINAL PAPER Changes of the susceptibility to lava flow invasion induced by morphological modifications of an active volcano: the case of Mount Etna, Italy Simone Tarquini • Massimiliano Favalli Received: 20 May 2009 / Accepted: 16 November 2009 / Published online: 26 November 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Changes of the susceptibility to lava flow invasion at Mount Etna are quantified by using lava flow simulations on four Digital Elevation Models documenting the morphostructural modifications of the volcano in the time interval 1986–2007. The probabilistic code DOWNFLOW is used to derive the areas invaded by several thou- sands of lava flows obtaining, for each DEM, maps of the susceptibility to lava flow invasion and of the lava flow hazard. These maps show, for the first time, the evolution of these surficial properties with time, and render a quantitative image of the effects of topographic changes on the preferential lava flow drainage paths. The results illustrate how the emplacement of new lava flows and the growth of scoria cones affect the probability of inundation by lava flows. We conclude that the persistent activity of this volcano requires a frequent updating of the topography for a reliable lava flow hazard assessment. Keywords Lava flow simulation  Digital Elevation Model  Lidar  Time series  Lava flow hazard maps 1 Introduction Several basaltic volcanoes, all around the world, are characterized by recurrent effusive eruptions which pose a threat to urbanized areas (e.g., Kilauea in Hawaii, Mount Etna in Sicily, Mount Cameroon in Cameroon, and Nyiragongo in Democratic Republic of Congo). Since the work of Wadge et al. (1994), a number of authors have made large sets of lava flow simulations to quantify the susceptibility to lava flow invasion (Felpeto et al. 2001; Favalli et al. 2006, 2008, 2009a, b; Crisci et al. 2008). The topography of the volcano plays a major role in determining the lava flow simu- lation outcomes (Macedonio et al. 1990; Felpeto et al. 2001; Miyamoto and Papp 2004; S. Tarquini (&)  M. Favalli Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Via della Faggiola 32, 56126 Pisa, Italy e-mail: tarquini@pi.ingv.it 123 Nat Hazards (2010) 54:537–546 DOI 10.1007/s11069-009-9484-y