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MARS TECTONICS & VOLCANOLOGY Zachary Gallegos University of New Mexico / Mars One Mars Orbiter Laser Altimeter Map Plate Tectonics • Lithospheric plates sliding on the asthenosphere, above the mantle • Exists on Earth • Theory proposed in the early 1900’s • Does it exist on other bodies in the solar system? Plate Tectonics • Recycles material • Regulates the atmosphere • CO2 sequestration and output • Linked with mantle convection • Push new material to surface at divergent boundaries • Pulls old material into the Earth at convergent boundaries Tectonics of Earth • Picture of plates Plate boundaries • Divergent • Spreading apart • Convergent • Moving together • Strike-slip • Sliding past Divergent • Mid-Atlantic ridge • Oceanic • East African Rift • Continental • Rio Grand Rift • Continental Convergent • Mariana Islands/Trench • oceanic-oceanic • Pacific Northwest • oceanic-continental • Himalayas • continental-continental Strike-slip • San Andres fault • right lateral Plate Tectonics of Mars Tectonics of Mars • Mars seems to lack global, Earth-like tectonics • Too small? • Not enough water? • Large scale faulting • HUGE scale rifting Topography • Mars’ planetary dichotomy • Not tectonic in origin • Bolide impact , water resurfacing • Slow sloping at the dichotomy • not pronounced • Earth’s dynamic lithosphere • Tectonic in origin • Steeply sloping at the margins • Continental and oceanic crust Magnetics • Mars lacks a current magnetic field • Magnetic reversals recorded on Earth Magnetics • Possible magnetic reversals recorded in early Martian crust Interior of Mars • Smaller/colder • Less water Faulting • Tectonic movement • Normal (extension) • Reverse (compression) • Strike-slip (lateral) Faulting on Mars • Thrust faulting • Amenthes Rupes • Normal faulting • Circum-Tharsis • Strike-slip faulting?? • Within Valles Marineris Faulting on Mars • Circum-Tharsis • Extensional faulting Valles Marineris • Giant tectonic fissure in the crust • Not the result of plates • Result of Tharsis uplift • Length: > 4,000km • Width: > 200km • Depth: > 7km • Largest known valley in the solar system Valles Marineris • Nearly ¼ or the planets circumference • Nine times longer than the grand canyon Vallis Marineris Volcanology • Study of volcanoes • Volcanoes bring new material to the surface from below • Lava, ash, gas Volcanology of Earth • Most of Earth’s volcanism is related to plate tectonics • Divergent and convergent boundaries Volcanology of Mars • No planetary tectonics • Shield forming • Hot spot volcanism (e.g. Hawaii) • Mostly basaltic in compositions • From ultramafic komattiatic to dacitic Rocks and Minerals • Mars has a different volcanic signature than Earth Why Basalt? • Hot spot volcanism produces basalt Volcanism and Tectonics • With no tectonics, volcanoes grow to enormous size Montes • Mons are large shield volcanoes • Earth analogue: Hawaii • Gentle slopes < 6° Ascraeus Mons Pavonis Mons Arsia Mons Tholi • Tholus is a term for smaller, dome shaped volcanoes • Older than Mons • Buried by later flows • Steeper flanks • Different material than Montes? • Less material than Montes? Patera • Term given to small volcanoes with large calderas • Latin translation: shallow drinking bowl • Larger calderas than the tholi • Probably represent larger volcanoes • Buried beneath flows and sediment Rootless Volcanoes & Pseudocraters • Show no sign of magma conduit • Analogues on Earth erupt due to a magma body flowing over a surface or subterranean water source Martian Volcanic Provinces Tharsis • Largest volcanic province on Mars • 25% of the planets surface • Avg. 7-10km above datum • Youngest flows on Mars Tharsis Arsia Mons Olympus Mons • Largest mountain in the solar system • Height: > 22km • Diameter: > 500km • Slope: ~ 4° • 6 nested calderas • 3.5km deep Alba Mons • North of Tharsis buldge • Very low slopes ~ .5° • 1600km across • Rises 3km above plains Elysium • Second largest volcanic province • 1,700x2,400 km • Elysium Mons • 13km high • Hecates Tholus • North • Albor Tholus • South Syrtis Major • 1200km across • 2km high • 2 calderas • Nili Patera, Meroe Patera • Silica rich rocks • Dacite & Granite Isidis Basin Highland Patera • Near the Hellas impact basin • Impact induced volcanism along fractures? Arabia Terra • Low relief Patera • Structures that look like Earth’s supervolcanoes • e.g. Eden Patera Questions? Geography of Mars Volcanic Provinces Exploration Sites
