In 2018, Hawaii's most active volcano took scientists by surprise. Lava started spewing out, not from the summit, but 50km away on the lower slopes of the volcano. This unexpected eruption destroyed farmland, roads and over 700 homes. Since then, volcanologists have been piecing together the events that triggered it. Using GPS trackers, high-speed cameras, chemical analysis and more, researchers have learnt what happens when volcanic craters collapse and how magma can move not just vertically but horizontally underneath a volcano. These insights help us to understand other similar volcanoes in Iceland, Italy and La Reunion. The hope is that next time Kilauea or one of these other volcanoes erupts, we will be better prepared.