Nodirectevidenceforpresentdayvolcanicactivity sapas

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Unformatted text preview: vidence of powerful tectonic forces likely driven by convection in Venus’s interior No direct evidence for Earth­like plate tectonics. Fractured region. Area is 40 km wide. “Tessera” - folds that appear to predate the large­scale volcanic plains that embay them Impact crater (D=37 km) split apart by tectonic forces. Venus: Volcanism Venus: Volcanism Hundreds of thousands of volcanoes. Volcanism is widespread and planetwide. Vast “mare­like” lava plains dominate. Many individual cones and mountains, “pancake domes” Coronae formed by upwelling of mantle, downwelling of lithosphere (or both). No direct evidence for present­day volcanic activity (?). Sapas Mons volcano “Pancake Domes” Cinder cone field. Each cone D ~ 1 km “Miss Piggy’s Face” Corona Venus: Erosion Venus: Erosion Evidence for surface erosion includes: Wind streaks Dune fields Long channels carved into bedrock No H2O! So erosion must indicate the action of wind and molten lava Surface winds very weak: long timescales Deep, long lava channels: long timescales Lava channels, some 1000s of km long Wind streak behind 5 km volcano Venera surface photo Venera 13 Venera 14 Mars Earth/Mars Comparison Earth/Mars Comparison Martian Moons Phobos (Fear) Deimos (Panic) Global Topography Global Topography Surface Ages from Crater Counting Surface Ages from Crater Counting Mars has a thin (~6 mbar) atmosphere of mostly carbon dioxide Liquid Water Not Stable on Mars Today Layering Layering Layering Layering Layering Layering Water­carved features Water­carved features Water­carved features Water­carved features Water­carved features Water­carved features Geologic Composition from Remote Sensing Geologic Composition from Remote Sensing Geologic Composition from Remote Sensing ­ Geologic Composition from Remote Sensing ­ Hematite An Ancient Wet Mars? An Ancient Wet Mars? Liquid Water Not Stable on Mars Today Modern Subsurface Water Modern Subsurface Water Discussion Questions for Today Discussion Questions for Today How can we see through the clouds of Venus, and what is actually imaged? What kind of structures occur in the Venusian crust, how are they distributed, and what do they signify? Why did Venus turn out so different from the Earth? What does the population of impact craters on Venus suggest about its history? Why do we think the pressure and temperature environment on Mars was different in the past from what it is today?...
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This note was uploaded on 11/10/2011 for the course GEOL 380 taught by Professor Mcsween during the Spring '11 term at University of Tennessee.

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