Caldera Blanca in Lanzarote

Volcanic landscape in Lanzarote, Spain, during ESA's Pangaea geological training for astronauts.

Calderas represent volcanoes that erupted very violently. Because so much material escaped in a single event, the empty magma chamber was no longer able to support its roof. The roof collapsed, forming this big broken rim. But the magmatic activity wasn’t over yet – at the centre of the caldera crater we can see a dome, where more magma upwelled below the surface, raising and fracturing the ground.