Shapes of Venusian “pancake” domes imply episodic emplacement and silicic composition
Article first published online: 7 DEC 2012
Copyright 1993 by the American Geophysical Union.
Geophysical Research Letters
Volume 20, Issue 4, pages 261–264, 19 February 1993
How to Cite
- Issue published online: 7 DEC 2012
- Article first published online: 7 DEC 2012
- Manuscript Accepted: 23 DEC 1992
- Manuscript Received: 1 DEC 1992
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 of a 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 represent 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 dome growth is found almost exclusively in lavas of dacite to rhyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.