Fluid dynamics in volcanology (wager prize lecture) |
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| Authors: | R S J Sparks |
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| Institution: | 1. Department of Earth Sciences, University of Cambridge, CB2, 3EQ, Cambridge, England
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| Abstract: | Fluid motions are important in virtually all volcanic processes. Attempts to understand the mechanism of volcanic activity or the origin of magmas generally require knowledge of fluid dynamics. The use of fluid dynamics is illustrated by considering the Reynolds numbers of some volcanic fluid flow systems. The physics of high Reynolds number buoyant plumes is found to be important in situations ranging from the rise of eruption columns in the atmosphere to the replenishment of basaltic magma chambers. Application of theoretical and experimental work on plumes enables eruption rates to be deduced from eruption column heights and new hypotheses on the origin of some magmatic ores to be put forward. The influence of Reynolds number on the behaviour of lava is also discussed with application to the origin of Archaean komatiite lavas. Komatiite lavas are argued to have flowed in a turbulent manner whereas modern basalt lavas nearly always flow by laminar shear. The turbulent character of komatiites seems to provide an explanation for the origin of associated nickel-sulfide mineralization in komaiites by melting and assimilation of sulfide-rich sediment. This hypothesis depends on komatiite flow having had a high Reynolds number. |
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