Formation of Mangala Fossa, the source of the Mangala Valles, Mars: Morphological development as a result of volcano-cryosphere interactions

[1] The morphology of the Mangala Fossa graben forming the source of the Mangala Valles implies that two episodes of graben subsidence took place, each induced by lateral dike intrusion from Arsia Mons. Quantitative modeling suggests that graben boundary faults breaching the cryosphere provided pathways for water release from an underlying aquifer at a peak rate of 10 m s . In the first event, the graben subsided by 200 m, and water carrying a thin ice layer filled the graben, overflowing after 2.5 hours, mainly at a low point on the north rim. This captured the water flux, eroding a gap in the north wall which, with an erosion rate of 100 mm s 1 and a duration of 1 month, was 250 m deep by the end of water release. Erosion of the graben floor also took place, at 20 mm s , lowering it by 50 m. Subsequently, heat from the cooling dike melted cryosphere ice, causing a further 150 m of subsidence on compaction. In the second event, with a similar duration and peak discharge, the graben again subsided by 200 m and filled with ice-covered water until overflow through the gap began at a water depth of 350 m. The gap was eroded down by a further 400 m, and the floor was eroded by a further 50 m. Finally, heat from the second dike sublimed cryosphere ice, lowering the floor by 100 m. In places, combined erosion and subsidence of the graben floor exposed 200 m of the first dike.