Formation of Olympus Mons and the aureole-escarpment problem on Mars

Based on morphologic interpretation of Viking Orbiter images, it is postula ted that on the summit area of Arsia Mons, Mars, there is a several kilomet er thick ice cover. In addition, numerous linear striae on the flanks of Ar sia Mons resemble terrestrial "washboard moraines," behind which there may be substantial dead-ice deposits. This implies that glacier phenomena are a ctive in the Tharsis region. These features may have bearing on the formati on of the aureole deposits of Olympus Mons, Olympus Mons has been the cause of dispute among geologists for years, and several contrasting models have been proposed to explain the up to 10-km-high distal escarpment and broad lobate aureole deposits below. One model by Hedges and Moore (1979) assumed 23-km-thick ice under which volcanism proceeded at an early stage to build Olympus Moils, thereby leading to the growth of the high cliff section. It has been argued that the origin of the aureole has not been satisfactorily explained. Modifications of the Hedges and Moore hypothesis are proposed t o explain some aspects of both the aureole formation and the escarpment at the lava-aureole boundary. The assumption is made that volcanism that persi sted was mostly localized on the Olympus Mons massif throughout the aureole development, and that a blanket of ice and wind-blown dust covered the low er flanks of the volcano. Deposition of volcanic products on the flank blan ket led to faulting and sliding of material away from the summit area, ther eby creating the aureole deposits and scarp, Further eruptions of lavas in the summit area substantially elevated the cliff segment, and additions of lavas off the cliffs into the vying area led to further creeping of the low er flank region, thus generating the vast aureoles, Therefore, the aureole formation succeeded and resulted from Olympus Mons volcanic activity, and i s one of the youngest features of Olympus Mons and not older, as has been p ostulated.