VOLCANISM ON MARS: The Tharsis Region and Olympus Mons A view of Olympus Mons

OUTLINE ABOUT OLYMPUS MONS Dimensions Geological Features EVIDENCE Equal Evidence Supporting Volcanism Implications (Geological & Environmental) READING Different Interpretations Based on Evidence Questions? DISCUSSION Accuracy of Data, Evidence & Results Improvements CONCLUSIONS

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~70 km ~10 km high ~26 km (16 mi) high shield volcano The Tharsis Region rises >10 km above the surrounding plains and is ~4,000 km wide Olympus Mons is ~624 km (374 mi) in diameter The volume of Olympus Mons is ~100 times greater than Mauna Loa, Hawaii (the entire Hawaiian island chain can fit inside the volcano) Above the scarp, the slope is only 2-3°

GEOLOGIC SEQUENCE Upper Amazonian – Slow transfer of heat from the deep intrusive zone to the surface creating a long-lived volcanic province Middle Amazonian– Lava plain filling and isostatic rise associated with deep crustal intrusion? Lower Amazonian – Formation of large circum-Olympus aureole deposits Upper Hesperian – Emplacement of preaureole extrusive lava flows Lower Hesperian – Upper Noachian Crustal destruction, minor faulting followed Middle Noachian by radial faulting, wrinkle ridges, polar Lower Noachian – deposits, extension, deformation & intense faulting near Olympus Mons

Different Ideas Volcanoes are long dead Neukum & Wise (1976) – Volcanoes are long dead Tharsis is a “warm corpse if not a fire-breathing geologic entity” Carr et al. (1977) – Tharsis is a “warm corpse if not a fire-breathing geologic entity” Tectonism of the Tharsis spread over the last 3-4 b.y. implies that there was a slow winding down of tectonic and volcanic activity, or that this activity occurred as a rapid early slowdown which is almost complete. Or, it could also reflect a continuous low level of tectonic activity which continues at present Puzzling origin of the volcanic basal cliffs of Mars in relation to the aureole: Wind Feature? Faulting? Erosional Encroaching? Uplifting? Problems… The duration of volcanism and changes in structural models

CONCLUSIONS Discussion Summary There is much still to be learned about the geologic history of Mars. The issues presented today are still great mysteries that have yet to be solved. All of the credible evidence available can support more than one plausible (or implausible) model. Though, until we can get geologists on Mars to survey the region, we have to keep making assumptions based on terrestrial comparisons of similar tectonic features and processes. Everything that we “know” may not be what we expected at all… (Experiment in Observational Techniques) Everything that we “know” may not be what we expected at all…