Lava flows are outpourings of molten rock, or magma. On Earth, the overwhelming majority have silicate compositions, for which common melting temperatures are in the range 800-1200°C; lavas of sulphur and of carbonate compositions also occur at lower temperatures (about 150°C for sulphur and 600°C for carbonatite), but these are extremely rare and are not important as far as general hazard studies are concerned. First applied at Vesuvius, the word “lava” is derived from the italian lavare (to wash), ironic since the washing normally meant cleaning away the fruits of human labour (Kilburn, 2000).