The landscape of Lycus Sulci, the ‘Lycian furrows’ to the northwest of the largest volcano on Mars – the almost 22-kilometre-high Olympus Mons – tells the story of a catastrophic breaking off and sliding down of the lower, several thousand-metre-high flanks of Olympus Mons in the distant past. Planetary scientists suspect that the slides were triggered several hundred million years ago by large quantities of low-viscosity lava that flowed down the flanks of Olympus Mons. These lava flows probably accumulated over strata that contained large amounts of water in the form of ice, similar to permafrost on Earth. The volcanic heat melted this ice, causing the rim areas of the volcano to become unstable and break away. This in turn caused large masses of rock to slide down into the landscape of Amazonis Planitia.