Quentin Cooper joins Open University scientists on Mount Etna, who have been monitoring Europe's most active volcano for more than 30 years. They visit a fissure on the eastern flank which is slowly producing lava along an underground tube and climb to the summit, which rises and falls under the combined effects of gravity and molten magma. If a giant landslide were ever to reach the sea it could result in a tsunami around the Mediterranean. The slope now seems to have stabilised, but Etna is not a tame volcano and only through long-term monitoring will scientists fully understand its ways.