Emplacement of Volcanic Domes on Venus
Emplacement of Volcanic Domes on Venus
Previously Published Material: A portion of the findings in this abstract were presented at the 2014 Lunar and Planetary Science Conference in The Woodlands, TX, USA. As of the submission date of this abstract, none of the findings are under review and they have not been recently accepted by a scientific journal.
Abstract ID#: 36124
English Abstract:
One key to understanding the resurfacing history of Venus is placing firmer constraints on the emplacement timescales of visible volcanic features. 175 steep-sided domes, with diameters ranging from 19-94 km and estimated thicknesses as great as 4 km, have been identified on Venus. These domes are thought to be volcanic in origin. Among the unanswered questions surrounding their formation are their composition, emplacement duration, and the rheology of the lava that formed them. Rheologically speaking, maintenance of 1-4 km thick flows necessitates higher viscosity lavas, while the domes’ smooth upper surfaces imply the presence of lower viscosity lavas. We have investigated the emplacement of volcanic domes on Venus, exploring the effect of boundary conditions on a similarity solution of the Boussinesq equation for pressure driven fluid flow in a cylindrical geometry. The new approach used here addresses time dependent changes in lava viscosity due to cooling and eliminates singularities inherent in previous models for dome relaxation. Two distinct scenarios are explored: one in which a constant volume of fluid (i.e., lava) is rapidly emplaced onto the surface, and another in which the volume of lava on the surface increases over time (i.e., a volumetric flowrate approach). We compare theoretical dome thickness profiles for radially expanding Newtonian fluid to the shape of a typical Venus dome. For the constant volume approach, we find that at the onset of relaxation, bulk lava viscosities lie between 1010-1016 Pa-s. Results for the volumetric flowrate scenario suggest a bulk lava viscosity of 1012 - 1013 Pa-s and emplacement times of approximately 2 - 16 years. Because the chilled lava crust can increase the apparent viscosity of lava flows up to four orders of magnitude greater than the actual viscosity of the fluid lava, our results suggest dome compositions more consistent with terrestrial basaltic andesites than rhyolites.