The volcanic history of Olympus Mons from paleo-topography and flexural modeling

Paleotopography and flexural modeling are here used to constrain the formation history and eruption rates of Olympus Mons, the tallest shield volcano on Mars. The timing of the initiation of significant edifice construction is constrained using lava flows whose paths deviate significantly from the down-slope direction of the present-day flexural trough, and thus are classified as topographically discordant. Flexural models are used to place limits on the fraction of Olympus Mons that could have been present at the time of emplacement of one strongly discordant flow. Comparison of the predicted flexural response with the paleotopography indicates that no more than 29-51% of the volume of Olympus Mons could have been present at the time the discordant flow was emplaced. The end of the primary edifice construction stage is constrained by the formation of the aureole deposits, which are inferred to post-date the bulk of the volcano. The ages of 3.67-0.10+0.05Ga for the discordant flow and 2.54-0.69+0.55Ga for the aureole deposit span the period during which the majority of Olympus Mons formed, a period of approximately 1.13-0.65+0.74Gyr. The resulting eruption rate of 0.003-0.015km³/yr is similar to that observed in terrestrial hot-spot volcanism, supporting a similar geodynamic mechanism driving shield-forming volcanism on Earth and Mars. After this period, the rate of volcanic resurfacing dropped off considerably, but low levels of volcanic activity have been maintained through the last several hundred million years.