Tectonics of Venus

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Tectonics of Venus
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Earths Sister Planet

• Similarities
• Terrestrial
• Size
• Density
• Relative distance to the Sun
• Relatively young surfaces

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Can you say Hell?

• Average surface temperature 4500 C
• Atmospheric Pressure 90 times Earths
• No Water
• Sulfuric Acid Clouds
• No magnetic field
• Retrograde rotation
• Form of tectonism

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Definition

• Tectonics is the study of large scale
  processes that collectively deform the planets
  Surface

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We are in Agreement

• Venusian surface features are younger than 1 GA
• Lithosphere relatively thick 200 km
• No evidence for present day plate tectonics
• Present day hot spot volcanism

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Landscape of Venus (Herrick)

• Venus
• Tesserae
• Plains
• Rift-volcano-coronae zones

• Earth
• Continents
• Oceanic plates
• Hot spots

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Tectonic Models

• Diapiarism over time (Hansen 2003)
• Correlation between climate change, surface
  temperature, and Tectonism (Solomon, et al 1999)
• Subduction to flood basalts to hot spot volcanism
  (Herrick 1992, also Basilevsky and Head 2002)

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Climate Change Model

• Large flood basalt volcanic event 700 Ma
• Greenhouse gases expelled
• Driving force for surface topography is
  differential between surface temp and mantle temp

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Diapirism Model

• Deformation of surface over time by diapirs.
• Two types
• Thermal (responsible for larger features crustal
  rises and plateaus)
• Compositional (responsible for smaller features
  Coronae)
• Venusian Uniformitarianism

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Subduction to Hot Spot Model

• Prior to 800 Ma active subduction and plate
  tectonics
• Subduction ceased but flood lavas flowed from
  spreading centers (relatively short lived event)
• Present day hot spot volcanism

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Conclusions

• Using earth tectonic and deformation processes
  not a good model
• Loss of water is key, puts the brakes on
  subduction
• Low to mid grade metamorphic termperature
  conditions at the surface!
• No brittle/ductile transition zone, everything
  behaves plastically even at surface
• The Herrick model is the most likely

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References

• Basilevsky, Alexander T., Head, James, W., 2002
• Hansen, V. L., 2003
• Herrick, Robert R., 1994
• Solomon, Sean C., Bullock, Mark A., Grinspoon,
  David H., 1999