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P. Allard, Groupe des Sciences de la Terre, Laboratoire Pierre Sue, CNRS-CEA/DRECAM
M. Burton, F. Muré, A. La Spina, Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy

News regularly point out all the beauty but also the potential dangers of volcanic eruptions. If one can appreciate the show of these natural phenomena, one also seeks to understand them better in order to protect the neighbouring populations and to evaluate their impact on the climate evolution.

Eruptions at Stromboli (Italy) occur as periodic explosions (~15 mn) projecting fragments of molten lava to a few hundred meters above the crater. This type of explosions, so-called "Strombolian", is observed on many volcanoes worldwide, among which  Mount Etna as again verified recently. The driving mechanism of the explosions is well known: large gas pockets (slugs) that are formed by coalescence of small bubbles at depth in the magma rise rapidly across the volcanic conduits and bursts explosively while reaching the surface. However, the depth of origin of these gas slugs remained uncertain; it  was indirectly estimated from the analysis of seismic and acoustic signals associated with the explosions. In a new study published in "Science" (July 2007, [1]), researchers from the Pierre Sue Laboratory (CNRS-CEA, Saclay) and the National Institute of Geophysics and Volcanology of Italy (INGV, Catania) determine for the first time the depth of origin of strombolian explosions.



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