Geophysics and Tectonics Seminar winter-2014

With Earth-like size and density, Venus should be Earth’s twin. Instead, it lacks plate tectonics and is shrouded by a hot, dense atmosphere with a run away greenhouse. The dramatic divergence of such initially similar terrestrial planets holds lessons for predicting exoplanet behavior. The history of volatiles is clearly central to understanding climate, and also has a major effect on interior evolution. Venus’ atmosphere has lost significant water, yet the interior may have more water than Earth. What are the constraints on water in the interior? Has lithospheric recycling and thus possible volatile recycling occurred? The initiation of subduction is both the gateway to plate tectonics and a key link between interior convection and lithospheric rheology. Numerous potential subduction sites have been identified on Venus. Most of these zones occur in association with corona (possible small-scale mantle upwelling features) and extensional zones. In this talk I will discuss constraints on water in the interior, the evidence for (and against) subduction, and a ‘new’ model for understanding the link between plumes and possible subduction on Venus. This interpretation is based on 1) laboratory fluid dynamics experiments that couple convection and lithospheric deformation and 2) evidence for current volcanism, plumes and possible subduction from gravity, altimetry, radar images and surface emissivity.