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| Titel |
Dynamics of eruptive pulses - A case study of the second explosive phase of the 2010 Eyjafjallajökull eruption (Iceland) |
| VerfasserIn |
Tobias Dürig, Magnús Guðmundsson, Sven Karmann, Bernd Zimanowski, Pierfrancesco Dellino, Martin Rietze, Ralf Büttner |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089870
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| Publikation (Nr.) |
 EGU/EGU2014-4083.pdf |
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| Zusammenfassung |
| Current ash plume models of long-lived eruptions usually consider sustained ash plumes to be
a continuous steady emission of tephra at the volcanic vent. The 2010 eruption of
Eyjafjallajökull volcano, however, often displayed pulsating activity, where emissions
from the vent occurred by frequent but discrete bursts (with pulses in the order
of seconds) that merged at higher altitude in a sustained eruption column. High
resolution near-field video recordings of the vents, taken from a distance of ~850m
during the second explosive phase from 8–10 May and supplemented by aerial
observations, were used as a case study to describe the mechanism of such pulsating
eruptions. The dynamics of discrete pressurized jets were characterized and their
pressure history quantified between discharge from vent until they reached the height
of transition at ~100m, where the expanding regime turned into a convective
buoyant one. It is suggested that during the analyzed initial expansion phase of
eruption, a rapid decompression of the pulses caused a significant decrease in particle
volumetric concentration within the jets, allowing and enhancing further-up air
entrainment and buoyancy and leading to the establishment of dilute ash plumes that
eventually merged and form the quasi-continuous eruption column. Based on the results
and conclusions of our case study we examine how to link the eruption source
parameters of multiple discrete expansive jets to the over-all mass eruption rate
derived by “classical” continuous ash plume models (being in the order of ~104
kg/s). Furthermore, the implications for real-time assessment by using near-field
monitoring systems under pulsatory eruption conditions are discussed. Finally, the
expansion dynamics of the analyzed pulses are compared to those of pulses generated in
large-scale experiments designed for reproducing explosive magmatic eruptions,
allowing us to evaluate the strengths and restrictions of using such experimental
simulations for calibrating near-field sensors to pre-set eruption source parameters. |
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