The date 28 December 2002, heralded the onset of a 7-month-long effusive eruption at Stromboli volcano in Italy. The onset was accompanied on 30 December by a large landslide (Figure 1). This landslide produced a tsunami that damaged the villages on Stromboli and affected coastal zones around the southern Tyrrhenian Sea. Following the landslide, the eruption was mostly characterized by effusive activity with lava flows extending from vents between 500 and 650 m above sea level. Simultaneously, Stromboli's typical explosive activity died out, with no explosions from the summit craters during the initial months of the eruption. However, a major explosive event on 5 April 2003 caused considerable alarm. Prior to the eruption, 95% of all seismic events could be correlated with visible explosions. However, during the first months of 2003, although seismicity related to magma-gas dynamics in the conduit remained at high levels, no explosions were observed. Stromboli's system is considered to be extremely stable, being associated with regular, mildly explosive, Strombolian eruptions. The absence of explosions from the summit craters, along with abundant lava flow and collapse of part of the volcano flank, were thus uncharacteristic for Stromboli.