Download Tectonics of Venus

Tectonics of Venus
Earth’s Sister Planet
Similarities:
Terrestrial
Size
Density
Relative distance to the Sun
Relatively young surfaces
Can you say Hell?
Average surface temperature 4500 C
Atmospheric Pressure 90 times Earth’s
No Water
Sulfuric Acid Clouds
No magnetic field
Retrograde rotation
Form of tectonism
Definition
Tectonics is the study of large scale
processes that collectively deform the
planet’s Surface
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
Landscape of Venus (Herrick)
Venus
Tesserae
Earth
Continents
Plains
Oceanic plates
Rift-volcano-coronae
zones
Hot spots
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)
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
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
Subduction to Hot Spot Model
• Prior to 800 Ma active
subduction and plate
tectonics
• Subduction ceased but
flood lava’s flowed
from spreading centers
(relatively short lived
event)
• Present day hot spot
volcanism
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
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