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The ~4-ka Rungwe Pumice (South-Western Tanzania): a wind-still Plinian eruption

Fontijn, Karen
Ernst, Gerald G. J.
Elburg, Marlina A.
Mbede, Evelyne
Jacobs, Patric
Published in Bulletin of Volcanology. 2011, vol. 73, no. 9, p. 1353-1368
Abstract The ~4-ka trachytic Rungwe Pumice (RP) deposit from Rungwe Volcano in South-Western Tanzania is the first Plinian-style deposit from an African volcano to be closely documented focusing on its physical characterization. The RP is a mostly massive fall deposit with an inversely graded base. Empirical models suggest a maximum eruption column height HT of 30.5–35 km with an associated peak mass discharge rate of 2.8–4.8×108 kg/s.Analytical calculations result in HT values of 33±4 km(inversion of TEPHRA2 model on grain size data) corresponding to mass discharge ranging from 2.3 to 6.0×10^8 kg/s. Lake-core data allow extrapolation of the deposit thinning trend far beyond onland exposures. Empirical fitting of thickness data yields volume estimates between 3.2 and 5.8 km3 (corresponding to an erupted mass of 1.1–2.0×10^12 kg), whereas analytical derivation yields an erupted mass of 1.1×10^12 kg (inversion of TEPHRA2 model). Modelling and dispersal maps are consistent with nearly no-wind conditions during the eruption. The plume corner is estimated to have been ca. 11–12 km from the vent. After an opening phase with gradually increasing intensity, a high discharge rate was maintained throughout the eruption, without fountain collapse as is evidenced by a lack of pyroclastic density current deposits.
Keywords RungweTanzaniaPlinian eruptionsPhysical characterizationEruptive parametersWind-free conditionsTrachyte
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Research group Physical Volcanology and Geological Risk
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FONTIJN, Karen et al. The ~4-ka Rungwe Pumice (South-Western Tanzania): a wind-still Plinian eruption. In: Bulletin of Volcanology, 2011, vol. 73, n° 9, p. 1353-1368. https://archive-ouverte.unige.ch/unige:19467

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Deposited on : 2012-04-19

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