Melas Chasma shows evidence of multiple large-scale landslides that have created vast fan shapes of material (box 1). The smoother surface seen further into the basin display flow textures indicating that they were once deposited by liquid water, water ice or mud (box 2). Levees of sediment can also been seen here. On the high plateau at the top of the cliff, a few ancient valleys have been preserved (box 3). The orientation of the largest one is parallel to the edge of the cliff, which may indicate that the valley originally followed an old fault line. Light-coloured deposits are present in the basin and at elevated locations on the flank (box 4). These are sulphates, which could have formed in an ancient lake.