Interpretation of umbrella cloud growth and morphology: implications for flow regimes of short-lived and long-lived eruptions

Solène Pouget, Marcus Bursik, Christopher Johnson, Andrew J Hogg, Jeremy C Phillips, R Stephen J Sparks

    Research output: Contribution to journalArticlepeer-review

    Abstract

    New numerical and analytical modeling shows that the growth of a volcanic umbrella cloud, expressed as the increase of radius with time, proceeds through regimes, dominated by different force balances. Four regimes are identified: Regime Ia is the long-time behavior of continuously-supplied intrusions in the buoyancy-inertial regime; regime IIa is the long-time behavior of continuously-supplied, turbulent drag-dominated intrusions; regime Ib is the long-time behavior of buoyancy-inertial intrusions of constant volume; and regime IIb that of turbulent drag-dominated intrusions of constant volume. Power-law exponents for spreading time in each regime are 3/4 (Ia), 5/9 (IIa), 1/3 (Ib), and 2/9 (IIb). Both numerical modeling and observations indicate that transition periods between the regimes can be long-lasting, and during these transitions, the spreading rate does not follow a simple power law. Predictions of the new model are consistent with satellite data from seven eruptions and, together with observations of umbrella cloud structure and morphological evolution, support the existence of multiple spreading regimes.
    Original languageEnglish
    Number of pages19
    JournalBulletin of Volcanology
    Volume78
    Issue number1
    DOIs
    Publication statusPublished - 11 Dec 2015

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