Relating vesicle shapes in pyroclasts to eruption styles

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dc.citation.firstpage691
dc.citation.journalTitleBull Volcanolen_US
dc.citation.volumeNumber75en_US
dc.contributor.authorMoitra, Pranabendu
dc.contributor.authorGonnermann, Helge M.
dc.contributor.authorHoughton, Bruce F.
dc.contributor.authorGiachetti, Thomas
dc.date.accessioned2013-02-21T16:58:06Z
dc.date.available2014-02-22T06:10:03Z
dc.date.issued2013
dc.description.abstractVesicles in pyroclasts provide a direct record of conduit conditions during explosive volcanic eruptions. Although their numbers and sizes are used routinely to infer aspects of eruption dynamics, vesicle shape remains an underutilized parameter. We have quantified vesicle shapes in pyroclasts from fall deposits of seven explosive eruptions of different styles, using the dimensionless shape factor , a measure of the degree of complexity of the bounding surface of an object. For each of the seven eruptions, we have also estimated the capillary number, Ca, from the magma expansion velocity through coupled diffusive bubble growth and conduit flow modeling. We find that Ω is smaller for eruptions with Ca 1 than for eruptions with Ca 1. Consistent with previous studies, we interpret these results as an expression of the relative importance of structural changes during magma decompression and bubble growth, such as coalescence and shape relaxation of bubbles by capillary stresses. Among the samples analyzed, Strombolian and Hawaiian fire-fountain eruptions have Ca 1, in contrast to Vulcanian, Plinian, and ultraplinian eruptions. Interestingly, the basaltic Plinian eruptions of Tarawera volcano, New Zealand in 1886 and Mt. Etna, Italy in 122 BC, for which the cause of intense explosive activity has been controversial, are also characterized by Ca 1 and larger values of Ω than Strombolian and Hawaiian style (fire fountain) eruptions. We interpret this to be the consequence of syn-eruptive magma crystallization, resulting in high magma viscosity and reduced rates of bubble growth. Our model results indicate that during these basaltic Plinian eruptions, buildup of bubble overpressure resulted in brittle magma fragmentation.en_US
dc.description.sponsorshipNational Science Foundation EAR-1019872en_US
dc.description.sponsorshipNational Science Foundation EAR-0810332en_US
dc.embargo.terms1 yearen_US
dc.identifier.citationMoitra, Pranabendu, Gonnermann, Helge M., Houghton, Bruce F., et al.. "Relating vesicle shapes in pyroclasts to eruption styles." <i>Bull Volcanol,</i> 75, (2013) Springer-Verlag: 691. http://dx.doi.org/10.1007/s00445-013-0691-8.*
dc.identifier.doihttp://dx.doi.org/10.1007/s00445-013-0691-8en_US
dc.identifier.urihttps://hdl.handle.net/1911/70174
dc.language.isoengen_US
dc.publisherSpringer-Verlagen_US
dc.subjectvesicle shapeen_US
dc.subjectpyroclasten_US
dc.subjectBasaltic Plinian eruptionen_US
dc.subjectregularityen_US
dc.subjectcapillary numberen_US
dc.subjectbubble growthen_US
dc.subjectconduit flow modelen_US
dc.subjectmagma fragmentationen_US
dc.titleRelating vesicle shapes in pyroclasts to eruption stylesen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
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