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

Fontijn, Karen; Ernst, Gérald; Bonadonna, Costanza; Elburg, Marlina; Mbede, Evelyne; Jacobs, Patric

doi:10.1007/s00445-011-0486-8

Cited by 31 publications

(21 citation statements)

References 43 publications

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“…Geochemistry, Geophysics, Geosystems approximately 15-cm thick at~30 km from the volcano (Fontijn et al, 2011) with 1-to 3-cm deposition 115 km from the source. At least one tephra layer with a comparable major element composition to Aluto was found in lake cores~100 km south west of Aluto by Martin- Jones et al (2017; Figure 4).…”

Section: Eruptive Activitymentioning

confidence: 99%

Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift

McNamara

Cashman

Rust

et al. 2018

Geochem Geophys Geosyst

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Aluto is a silicic volcano in central Ethiopia, flanked by two large population centers and home to an expanding geothermal power plant. Here we present data from two lake sediment cores sampled 12 and 25 km from the volcano, which record at least 24 distinct eruptions in the Holocene. Tephra layers from the two cores are correlated using a variety of techniques, including major and trace element geochemistry as well as textural and morphological features from scanning electron microscopy‐backscatter electron imaging. The purpose is to provide a Holocene reference section for further tephrostratigraphic studies of the volcano as well as to provide information on eruption frequency. The lake cores suggest that Aluto has had a variable eruption rate, with three eruption clusters in the Holocene at ~3, 6.5, and 11 ka, with small Vulcanian‐to sub‐Plinian eruptions separated by larger, Plinian eruptions. We infer that the smaller tephras are likely the product of pumice cone‐ and dome‐forming eruptions. In addition, modern wind data suggest that the likely direction of an ash cloud from Aluto is to the west and south west, which is toward population centers and is in agreement with thickness data from the cores. We conclude that current records underestimate the volcano's eruptive history and that hazard assessments should be updated accordingly.

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Section: Eruptive Activitymentioning

confidence: 99%

Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift

McNamara

Cashman

Rust

et al. 2018

Geochem Geophys Geosyst

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“…Finally, and very importantly, the rifting process is associated with significant seismic and volcanic hazards for the densely populated rift valley (e.g., Fontijn et al, 2011;Hodge et al, 2015). The long border faults within thick strong crust may be capable of producing M w ∼ 8 earthquakes (Jackson and Blenkinsop, 1997;Hodge et al, 2015).…”

Section: Tectonic Backgroundmentioning

confidence: 99%

Acquisition of a Unique Onshore/Offshore Geophysical and Geochemical Dataset in the Northern Malawi (Nyasa) Rift

Shillington

Gaherty

Ebinger

et al. 2016

Seismological Research Letters

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The Study of Extension and maGmatism in Malawi aNd Tanzania (SEGMeNT) project acquired a comprehensive suite of geophysical and geochemical datasets across the northern Malawi (Nyasa) rift in the East Africa rift system. Onshore/offshore active and passive seismic data, long-period and wideband magnetotelluric data, continuous Global Positioning System data, and geochemical samples were acquired between 2012 and 2016. This combination of data is intended to elucidate the sedimentary, crustal, and upper-mantle architecture of the rift, patterns of active deformation, and the origin and age of rift-related magmatism. A unique component of our program was the acquisition of seismic data in Lake Malawi, including seismic reflection, onshore/offshore wide-angle seismic reflection/refraction, and broadband seismic data from lake-bottom seismometers, a towed streamer, and a large towed air-gun source. SCIENCE MOTIVATION AND EXPERIMENT SUMMARYThe primary scientific goal of the Study of Extension and maGmatism in Malawi aNd Tanzania (SEGMeNT) project is to examine the emergence and early evolution of two fundamental features of all divergent plate boundaries: magmatism and segmentation. Magmatism accommodates a significant percentage of plate separation at most midocean ridges and late-stage continental rifts. Likewise, transform faults demarcate discrete spreading segments in midocean ridges, which are broadly characterized by more robust magmatism at their centers than at their edges (Macdonald et al., 1988;Lin et al., 1990). Well-developed magmatic and tectonic segmentation is also observed in late-stage continental rifts and new ocean basins (Taylor et al., 1995;Ebinger and Casey, 2001;Keir et al., 2009), but little is known about the controls on the initiation and development of magmatism and segmentation in immature rifts. Our project is focused on addressing the following questions:• When, where, and why does magmatism initiate in rifts, and what is its role in accommodating extension? • What controls the development of tectonic segmentation in early-stage rifts? How is it manifested in 4D patterns of magmatism and deformation?To address the questions above, we acquired an integrated geophysical and geochemical dataset across the northern Malawi (Nyasa) rift in the southern part of the East Africa Rift system (EARS). Our team included universities and geological surveys in the United States, Malawi, and Tanzania. The following datasets were acquired as a part of the SEGMeNT project: onshore/offshore active and passive seismic data, long-period and wideband magnetotelluric (MT) data, continuous Global Positioning System (GPS) data, and geochemical samples. This is the first integrated geophysical and geochemical dataset acquired across and within any of the great African rift lakes that can constrain rift architecture and processes at a range of scales. TECTONIC BACKGROUNDThe northern Malawi (Nyasa) rift in the Western Branch of the EARS is an excellent locality to examine the early stages of rifting in str...

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“…Nonetheless, also the erupted mass for both layers A–B and A–F is not as well constrained by the model as for larger eruptions (e.g., Pululagua 2450 B.P. [ Volentik et al ., ] and 4 ka Rungwe Pumice [ Fontijn et al ., ]), with many relative RMSE minima associated with both an underestimation and an overestimation of the erupted mass as derived from empirical integrations (dashed lines in Figure ). Targeted inversions were run based on the ranges identified by both the minimum values of RMSE shown by Figure and empirical observations (see supporting information for more details).…”

Section: Physical Parameters and Eruption Classificationmentioning

confidence: 99%

Dynamics of wind‐affected volcanic plumes: The example of the 2011 Cordón Caulle eruption, Chile

et al. 2015

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The 2011 Cordón Caulle eruption represents an ideal case study for the characterization of long-lasting plumes that are strongly affected by wind. The climactic phase lasted for about 1 day and was classified as subplinian with plumes between~9 and 12 km above the vent and mass flow rate (MFR) on the order of~10 7 kg s À1. Eruption intensity fluctuated during the first 11 days with MFR values between 10 6 and 10 7 kg s À1. This activity was followed by several months of low-intensity plumes with MFR < 10 6 kg s À1 .Plume dynamics and rise were strongly affected by wind during the whole eruption with negligible upwind spreading and sedimentation. The plumes that developed on 4-6 and 20-22 June can be described as transitional, i.e., plumes showing transitional behavior between strong and weak dynamics, while the wind clearly dominated the rise height on all the other days resulting in the formation of weak plumes. Individual phases of the eruption range between Volcanic Explosivity Indices (VEIs) 3 and 4, while the cumulative deposit related to 4-7 June 2011 is associated with VEIs 4 and 5. Crosswind cloud and deposit dispersal of the first few days are best described by a linear combination of gravitational spreading and turbulent diffusion, with velocities between 1 and 10 m s À1. Downwind cloud velocity for the same days is best described by a linear combination of gravitational spreading and wind advection, with velocities between 17 and 45 m s À1. Results show how gravitational spreading can be significant even for subplinian and small-moderate eruptions strongly advected by wind and with low Richardson number and low MFR.

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

Cited by 31 publications

References 43 publications

Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift

Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift

Acquisition of a Unique Onshore/Offshore Geophysical and Geochemical Dataset in the Northern Malawi (Nyasa) Rift

Dynamics of wind‐affected volcanic plumes: The example of the 2011 Cordón Caulle eruption, Chile

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