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Hotspot evolution and Venusian tectonic styleBecause hotspots represent an important manifestation of heat loss on Venus, their geological evolution is of fundamental importance for any attempt to understand Venusian tectonics. Eistla Regio is an approximately 7500-km-long, moderately elevated region inferred to overlie one or more large mantle upwellings or hotspots. It also contains many shield volcanoes and coronae believed due to the rise of thermal plumes in the mantle. Central Eistla Regio includes two large volcanoes, Sappho and Anala, and several coronae in close proximity. Detailed mapping in this region results in two conclusions of tectonic significance: (1) Sappho and Anala occur near the intersection of two major extensional deformation zones, and (2) the coronae are older than the large volcanoes. Several of the coronae occur as a chain along Guor Linea, one of the major extensional deformation zones. Stratigraphic relationships indicate that the coronae began forming very soon after the emplacement of the widespread regional plains materials. Thus Central Eistla Regio was the site of a swarm of plumes that first formed coronae and then later formed shield volcanoes. The expected result of such a swarm would be thermal thinning of the elastic lithosphere with time. However, model results, geological observations, and gravity data suggest that the change from coronae to shield volcanoes was accompanied by a thickening of the lithosphere with time. This thickening is interpreted to be the result of global cooling of the lithosphere following the most recent episode of near-global resurfacing. The global cooling must have occurred faster than local heating of the lithosphere due to the impingement of thermal plumes.
Document ID
19950035559
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Mcgill, George E.
(University of Massachusetts, Amherst, MA United States)
Date Acquired
August 16, 2013
Publication Date
November 25, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: E11
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
95A67158
Funding Number(s)
CONTRACT_GRANT: NAGW-1965
CONTRACT_GRANT: NAGW-3532
Distribution Limits
Public
Copyright
Other

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