Geology of the Olympus Mons region of Mars

The origin of the extremely large perimeter scarp and surrounding aureole deposits of the Olympus Mons shield volcano have been mysteries since their discovery. Studies of Viking orbiter imaging, radar, and gravity acceleration data have provided a basis on which to address local stratigraphic, structural, erosional, and climatic history. In turn, geologic history, terrestrial analogs, and hypothetical simulations are used to ascertain the applicability of multiple working hypotheses. Mass movement emplacement of the aureoles is untenable for mechanical reasons, ash-flow deposition does not adequately explain the ridge and valley surface of the aureoles, and moberg-ridge volcanism requires a large ice-cap and an unlikely fracture pattern in basement rocks. A flood-lava model presented here can hypothetically explain: (1) the emplacement of the aureoles, (2) the formation of the surface ridge and valley structure, and (3) the presence of a near-surface source pluton to explain the positive gravity residual anomaly centered over a large, well-exposed aureole deposit.