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Planetary Geomorphology

Planetary Geomorphology. (Earth analogs and comparisons). CCC Planetary Science KMullins 2014. Planetary Volcanism. Surface expression of melting processes occurring within a planetary body

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Planetary Geomorphology

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  1. Planetary Geomorphology (Earth analogs and comparisons) CCC Planetary Science KMullins 2014

  2. Planetary Volcanism • Surface expression of melting processes occurring within a planetary body • Evidence that volcanism has modified the surface of all the terrestrial bodies and many of the icy bodies as well (cryo-volcanism) • Effusive • Lavas flows • Explosive • Pyroclastic eruptions CCC Planetary Science KMullins 2014

  3. Planetary Volcanism (cont’d) • Planetary conditions impact how volcanism manifests itself • Modify style of eruption • Distribution of erupted materials • Size or morphology of resultant deposits • Gravity • Atmosphere • Surface temperature • Magmatic composition CCC Planetary Science KMullins 2014

  4. Sources for volcanism • Cratering • Some impacts cause melting • Large impacts can reach mantle material • Usually results in dark, smooth crater floors or extended areas nearby • Differentiation • Thermal and gravitational separation • Residual heat from planetary formation • Direct link to volcanism and tectonics • Tectonics • Weakness in crustal rocks • Produce changing conditions in mantle areas • Pressure • Heat/friction • Partial melting • Introduction of volatiles CCC Planetary Science KMullins 2014

  5. Volcanic Features CCC Planetary Science KMullins 2014

  6. Components of a typical volcano • Cone • Caldera • Conduit • Magma Chamber • Flows • Dikes • Sills • Eruption Cloud • Tephra • Volatiles

  7. Comparison of Types of Earth Volcanoes CCC Planetary Science KMullins 2014

  8. Comparison of Earth and Mars Volcanoes CCC Planetary Science KMullins 2014

  9. Volcanic Compositions • Mafic (basalt) • Dark • Low silica content • Low viscosity • Fluid effusive flows • Localized pyroclastic (cinder) deposits • Gentle-sloping, onion-layered volcanoes (shield and/or cinder cones) • Intermediate (andesite) • Intermediate • Moderate silica content • Moderate viscosity • Alternating effusive & pyroclastic eruptions • Steep-sided, large volcanoes (stratovolcanoes and/or cinder cones) • Felsic (rhyolite) • Light • High silica content • High viscosity • Explosive, catastrophic eruptions • Sometimes thick restricted flows • Very steep-sided, localized volcanoes or large caldera systems (domes & caldera features) CCC Planetary Science KMullins 2014

  10. Shield Volcanoes • Largest volcanoes/mtns on Earth and in our SS • Hawaii, House Mtn. Sedona • Mafic or basaltic in composition • Low silica content • Low viscosity • Flow easily • Form cones with gentle slopes • Quiet eruptions • High temp lavas • Generated deep beneath the crust Image is a false color composite from Landsat ETM+ of the big island of Hawaii. Note caldera at center of image. CCC Planetary Science KMullins 2012

  11. Hawaiian Island Topography

  12. Volcanic Calderas • Calderas – volcanic vents at the top of volcanic cones from which lava extrudes on the surface from the magma chamber below • Collapse after eruption event is over producing a flat-floored or bowl-shaped depression • Often have flat, smooth floors • Result from cooling of lava “lakes” • Mars Olympus Mons caldera, upper right • African Rift Valley caldera, lower right • Inner Basin, San Francisco Peaks CCC Planetary Science KMullins 2012

  13. Lake Toba Caldera, Indonesia • ~100km long and 30km wide • 75,000ya erupted over ~2,000 km3 of volcanic material • Human genetic bottleneck?

  14. Olympus Mons, Mars • This picture clearly shows how large and flat Olympus Mons is • The volcano is ~27 km high • Over 20 times wider than it is tall • ~ Size of Arizona • The distinct cliff which marks the base of Olympus Mons is up to 6 km high CCC Planetary Science KMullins 2014

  15. Mt. Rainier (Earth) and Sapas Mons (Venus) • Strato-volcanoes/Composite cones • Mt. Fuji, Kilimanjaro, Vesuvius, Mt. St. Helens, SF Peaks • Andesitic composition • Intermediate silica content • More viscous lavas • Steeper slopes • Varied eruption styles • Interbedded • Pyroclastics • Extruded lava flows The upper image is from Landsat visible bands & shows snow as a bright signature. The lower image is a false-color radar image that shows the roughness of the surface. Note the bright (rough) circular deposits on the volcanoes slopes as opposed to the dark (smooth) signature of many of the flows beneath the younger, more silicic pyroclastic deposits. CCC Planetary Science KMullins 2014

  16. Cinder Cones • Basaltic to andesitic in composition • Sunset Crater, A1 Mtn., Strawberry Crater, Mirriam Crater, SP Crater • Very common, usually in groups • simple central vent structure • Small size • Pyroclastic eruption type • Cinder sized tephra with associated bombs • Often associated with flows Upper image is DEM of a small area of the SFVF in northern AZ. Lower image is a radar scene of cinder cone field on Venus. Note bright (rough) signature of pyroclastic deposits forming cones and smoother (smaller grain size) deposits farther out from central vents. CCC Planetary Science KMullins 2014

  17. Volcanic Domes • Felsic in composition • High silica content • High viscosity • Steep sided slopes • Large, rounded lobate toes • Short, stubby flow morphology Upper image, color coded DEM of Mt. Elden, Flagstaff, a dacitic indogenous and exogenous dome. Lower image, radar scene of Venus pancake domes. CCC Planetary Science KMullins 2014

  18. Lava Flows • Morphology • Short, stubby, high relief • Silicic in composition • High silica, high viscosity, don’t flow far • Exhibit rounded, lobate termini • Long, flat, low relief • Usually basaltic or basaltic-andesite in composition • Low silica, low viscosity, flat topographically and can be very long • Can be rough or smooth surfaced depending on temp and cooling regime • Follows topo of surface onto which they erupt • Layered and indicative of orientation of original surface Upper image is an aerial photo of the Cima field in the Mojave desert, CA. Lower image is a radar image from the flank of a larger composite cone on Venus. CCC Planetary Science KMullins 2014

  19. Lava Flows • Mafic • Low silica, low viscosity • Low relief • Often follow topography • Wrinkled, rough surface • Associated with cones and fissures • Small scale lobate toes • Can be 10’s to 100’s of km in length Upper image, color coded DEM of A-one Mountain west Of Flagstaff (Observatory Mesa flow). Lower image, terminal end of large flow on Mars near Olympus Mons. CCC Planetary Science KMullins 2014

  20. NE Section of SFVF

  21. Tharsis Volcanic Region of Mars • Giant volcanic plateau • Home to the SS largest volcanoes • Largest feature on Mars other than topo dichotomy • Related to VallesMarineris

  22. MOLA data of Mars • Note significant dichotomy of topography between N & S hemis • Significant age dichotomy • SS largest impact feature?

  23. Ceraunius Tholus and Uranius Tholus • Incised valleys and patterns suggest softer ash material • Both cones are partially buried by other lava flow material • Note deltaic material in oblate crater and partially buried craters

  24. Ulysses Patera • Note large caldera, post collapse impacts and cross-cutting graben • Size of caldera compared to cone structure suggests burial of lower cone in post-eruption lavas

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