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New Approaches to Inferences for Steep-Sided Domes on VenusNew mathematical approaches for the relaxation and emplacement of viscous lava domes are presented and applied to steep-sided domes on Venus. A similarity solution approach is applied to the governing equation for fluid flow in a cylindrical geometry for two distinct scenarios. In the first scenario, dome relaxation is explored assuming a constant volume of fluid (i.e. lava) has been rapidly emplaced onto the surface. Cooling of lava is represented by a time-variable viscosity and singularities inherent in previous models for dome relaxation have been eliminated. At the onset of relaxation, bulk dynamic viscosities lie in the range between 10(exp 10) - 10(exp 16) Pa s, consistent with basaltic-andesite to rhyolitic compositions. Plausible relaxation times range from 5 to 5000 years, depending on initial lava viscosity. The first scenario, however, is only valid during the final stages of dome relaxation and does not consider the time taken for lava to be extruded onto the surface. In the second scenario, emplacement and growth of a steep-sided dome is considered when the volume of lava on the surface increases over time (i.e. time-variable volume approach). The volumetric flow rate may depend on an arbitrary power of the dome thickness, thus embracing Newtonian as well as other rheologies for describing terrestrial and planetary mass flows. The approach can be used to distinguish between basic flow rate models for fluid emplacement. The formalism results in radial expansion of a dome proportional to t(sup 1/2), consistent with the diffusive nature of the governing equation. The flow at the front is shown to thicken as the front advances for a constant rate of lava supply. Emplacement times are intimately correlated with the bulk rheology. Comparison of the theoretical profiles with the shape of a typical dome on Venus indicates that a Newtonian bulk rheology is most appropriate, consistent with prior studies. However, results here suggest a bulk dynamic viscosity of 10(exp 12) - 10(exp 13) Pa s and emplacement times of approximately 2-16 years. Both scenarios investigated give emplacement times significantly less than prior estimates and compositions consistent with basaltic andesite.
Document ID
20170003177
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Quick, Lynnae C.
(Maryland Univ. Greenbelt, MD, United States)
Glaze, Lori S.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Baloga, Stephen
(Proxemy Research, Inc. Gaithersburg, MD, United States)
Stofan, Ellen
Date Acquired
April 7, 2017
Publication Date
March 29, 2016
Publication Information
Publication: Journal of Volcanology and Geothermal Research
Publisher: Elsevier
Volume: 319
ISSN: 0377-0273
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
GSFC-E-DAA-TN40488
Funding Number(s)
WBS: WBS 811073.02.01.04.44
CONTRACT_GRANT: NNG06EO90A
CONTRACT_GRANT: NNX09AE10G
Distribution Limits
Public
Copyright
Other
Keywords
steep-sided domes
viscous lava
Venus

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