A Global Survey of Lithospheric Flexure at Steep‐Sided Domical Volcanoes on Venus Reveals Intermediate Elastic Thicknesses
M. E. Borrelli, J. G. O’Rourke, S. E. Smrekar, Colby Ostberg
Abstract
Abstract Topographic flexure in response to vertical loads reveals key lithospheric properties, including elastic thickness and the heat flow from the interior. Flexural stresses that depend on elastic thickness may in turn control volcano morphology. One previous study predicted that steep‐sided domes on Venus usually form where the elastic thickness is ∼15–40 km. Coronae and large volcanoes may typically form at regions with lower and higher elastic thickness, respectively. We surveyed flexural signatures around steep‐sided domes and confirmed this hypothesis. Specifically, we extracted radial profiles of topography from Magellan altimetry data and a new elevation model derived from stereo images. Nearly 20% of the identifiable domes had topographic profiles that were amenable to flexural interpretations. We determined elastic thicknesses using a curve‐fitting algorithm and plate bending models that treat each volcano as either a Cartesian line load or an axisymmetric disc load. We used a yield strength envelope featuring brittle failure and ductile flow at the top and bottom of the lithosphere, respectively, to convert elastic thickness into mechanical thickness and surface heat flow. The average elastic thickness for domes not near coronae is ∼30 km, corresponding to a heat flow of ∼60 mW/m 2 . Coronae on Venus are typically associated with elastic thicknesses of <10–15 km. Domes near coronae yielded elastic thicknesses in that range, and higher heat flows than domes not near coronae. Ultimately, flexural signatures are probably abundant around volcanic and tectonic features and would be further revealed in higher‐resolution topographic data.