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The evolution of bubble size distributions in volcanic eruptions

Research output: Contribution to journalArticle

Original languageEnglish
Article numberPII S0377-0273(02)00404-3
Pages (from-to)1-23
Number of pages23
JournalJournal of Volcanology and Geothermal Research
Volume120
Issue number1-2
DOIs
DatePublished - 15 Jan 2003

Abstract

We review observations of bubble size distributions (BSDs) generated during explosive volcanic eruptions and laboratory explosions, as inferred from vesicle size distributions found in the end products. Unimodal, polymodal, exponential and power law BSDs are common, even in the absence of coalescence, and both power law and exponential distributions have been generated in the same eruption. To date theoretical models have proposed incompatible mechanisms for producing the various distributions. We here present a unifying mechanism. Data from our laboratory analogue experiments suggest that power law distributions are associated with highly non-equilibrium degassing. A numerical model is developed in which bubbles nucleate repeatedly and grow in the spaces between those of previous generations, where, in a non-equilibrium degassing scenario, the volatile concentration remains high. This process causes the BSD to evolve from unimodal, through exponential, into a power law. The exponent of the power law is a measure of the number of nucleation events, or the duration of the nucleation period compared with the timescale of bubble growth. The mathematical inevitability of the evolution from unimodal (Poissonian), to power law is discussed. The findings may resolve the apparent contradiction between the equilibrium degassing conduit flow models and the non-equilibrium degassing conditions derived from bubble growth models of explosive volcanic eruptions. The process of ongoing nucleation is the mechanism whereby the volcanic system maintains near-equilibrium in the case of rapid depressurisation and slow volatile diffusion. (C) 2002 Elsevier Science B.V. All rights reserved.

Additional information

Publisher: Elsevier Other identifier: IDS number 621TD

    Research areas

  • EXPLOSIVE ERUPTIONS, DEGASSING PROCESSES, DISTRIBUTION CSD, RHYOLITIC MELTS, BASALTIC LAVA, DYNAMICS, GROWTH, MAGMAS, ROCKS, CRYSTALLIZATION

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