Research supported by NASA Grant NAGW 529 from Planetary Geology and Geophysics Program and the National Science Foundation grant EAR 9018216.
Geophysical Research Letters
Volcanology -- Research, Lava flows, Geologic formations, Venus (Planet) -- Geology
The main evidence available for constraining the composition of the large circular "pancake" domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 venusian domes to sent a sampling of many stages during the growth of domes with comparable histories, and by plotting aspect ratio versus total volume, we find that the shapes of the domes are most consistent with episodic emplacement. On Earth this mode of me growth is found almost exclusively in lavas of dacite to rhlyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.
Fink, J. H., Bridges, N. T., & Grimm, R. E. (1993). Shapes of Venusian “pancake” domes imply episodic emplacement and silicic composition. Geophysical research letters, 20(4), 261-264.