Multiphase flow behaviour and hazard prediction of pyroclastic density currents

Lube, Gert; Bréard, E.; Ongaro, Tomaso Esposti; Dufek, Josef; Brand, Brittany D.

doi:10.1038/s43017-020-0064-8

Cited by 90 publications

(105 citation statements)

References 186 publications

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“…The alternative use of simplified PDC models is also problematic, because the uncertainty associated to oversimplified boundary conditions (i.e. inability to describe the complexity of the explosive source), poorly constrained empirical parameters, and model approximations is even larger, although the low computational cost makes it possible to perform thousands of simulations to explore the parameter ranges in a probabilistic framework (Dalbey et al 2008;Procter et al 2010;Neri et al 2015a, b;Ogburn and Calder 2017;Sandri et al 2018;Rutarindwa et al 2019;Lube et al 2020). However, the exploitation of massive supercomputers and high-performance computing techniques, and the availability of open-source and community software, are driving a new step forward towards quantitative, probabilistic hazard assessment using 3D multiphase flow models.…”

Section: Drawing Pdc Hazard Maps From Simulation Outputsmentioning

confidence: 99%

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Modelling pyroclastic density currents from a subplinian eruption at La Soufrière de Guadeloupe (West Indies, France)

et al. 2020

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We have used a three-dimensional, non-equilibrium multiphase flow numerical model to simulate subplinian eruption scenarios at La Soufrière de Guadeloupe (Lesser Antilles, France). Initial and boundary conditions for computer simulations were set on the basis of independent estimates of eruption source parameters (i.e. mass eruption rate, volatile content, temperature, grain size distribution) from a field reconstruction of the 1530 CE subplinian eruption. This event is here taken as a reference scenario for hazard assessment at La Soufrière de Guadeloupe. A parametric study on eruption source parameters allowed us to quantify their influence on the simulated dynamics and, in particular, the increase of the percentage of column collapse and pyroclastic density current (PDC) intensity, at constant mass eruption rate, with variable vent diameter. Numerical results enabled us to quantify the effects of the proximal morphology on distributing the collapsing mass around the volcano and into deep and long valleys and to estimate the areas invaded by PDCs, their associated temperature and dynamic pressure. Significant impact (temperature > 300 °C and dynamic pressure > 1 kPa) in the inhabited region around the volcano is expected for fully collapsing conditions and mass eruption rates > 2 × 107 kg/s. We thus combine this spatial distribution of temperature and dynamic pressure with an objective consideration of model-related uncertainty to produce preliminary PDC hazard maps for the reference scenario. In such a representation, we identify three areas of varying degree of susceptibility to invasion by PDCs—very likely to be invaded (and highly impacted), susceptible to invasion (and moderately impacted), and unlikely to be invaded (or marginally impacted). The study also raises some key questions about the use of deterministic scenario simulations for hazard assessment, where probability distributions and uncertainties are difficult to estimate. Use of high-performance computing techniques will in part allow us to overcome such difficulties, but the problem remains open in a scientific context where validation of numerical models is still, necessarily, an incomplete and ongoing process. Nevertheless, our findings provide an important contribution to the quantitative assessment of volcanic hazard and risk at La Soufrière de Guadeloupe particularly in the context of the current unrest of the volcano and the need to prepare for a possible future reawakening of the volcano that could culminate in a magmatic explosive eruption.

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Section: Drawing Pdc Hazard Maps From Simulation Outputsmentioning

confidence: 99%

“…One way to assess hazard and risk at vulnerable sites is through model-based appraisals of PDC invasion and maximum runout, and mapping of hazardous actions in the inundated areas (cf. Calder et al 2015;Takarada 2017;Lube et al 2020). Such hazard mapping has been developed both for quiescent volcanoes (e.g.…”

Section: Introductionmentioning

confidence: 99%

Modelling pyroclastic density currents from a subplinian eruption at La Soufrière de Guadeloupe (West Indies, France)

et al. 2020

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“…The dense basal layer of a PDC (the flow) is topographically constrained so that their path typically remains confined to within a pre-existing channel, while the dilute, upper layer of PDCs (the surge) is less topographically constrained. Models of PDC transport regimes are improving in their sophistication, with the newest conceptual models including an intermediate flow layer between the dense basal and upper dilute layers (Lube et al, 2020). From a hazards perspective, this is extremely important, as it means the dilute, upper layer can detach from the lower, gravity driven flow, climbing topographic barriers and travelling to places that the rest of the PDC cannot (e.g., Nakada and Fujii 1993, Loughlin et al 2002a,b, Dufek et al 2015, Jenkins et al 2016.…”

Section: Introductionmentioning

confidence: 99%

The hazards of unconfined pyroclastic density currents: a new synthesis and classification according to their deposits, dynamics, and thermal and impact characteristics

Lerner¹,

Jenkins²,

Charbonnier³

et al. 2022

Preprint

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Pyroclastic density currents (PDCs) that escape their confining channels are among the most dangerous of volcanic hazards. These unconfined PDCs are capable of inundating inhabited areas that may be unprepared for these hazards, resulting in significant loss of life and damage to infrastructure. Despite their ability to cause serious impacts, unconfined PDCs have previously only been described for a limited number of specific case studies. Here, we carry out a broader comparative study that reviews the different types of unconfined PDCs, their deposits, dynamics and impacts, as well as the relationships between each element. Unconfined PDCs exist within a range of concentration, velocity and temperature: characteristics that are important in determining their impact. We define four end-member unconfined PDCs: 1. fast overspill flows, 2. slow overspill flows, 3. high-energy surges, and 4. low-energy detached surges (LEDS), and review characteristics and incidents of each from historical eruptions. These four end-members were all observed within the 2010 eruptive sequence of Merapi, Indonesia. We use this well-studied eruption as a case study, in particular the villages of Bakalan, 13 km south, and Bronggang 14 km south of the volcano, which were impacted by slow overspill flows and LEDS, respectively. These two unconfined PDC types are the least described from previous eruptions, but during the Merapi eruption the overspill flow resulted in building destruction and the LEDS in significant loss of life. We discuss the dynamics and deposits of these unconfined PDCs, and the resultant impacts. We then use the lessons learned from the 2010 Merapi eruption to assess some of the impacts associated with the deadly 2018 Fuego, Guatemala eruption. Satellite imagery and media images supplementing fieldwork were used to determine the presence of both overspill flows and LEDS, which resulted in the loss of hundreds of lives and the destruction of hundreds of buildings in inundated areas within 9 km of the summit. By cataloguing unconfined PDC characteristics, dynamics and impacts, we aim to highlight the importance and value of accounting for such phenomena in emergency management and planning at active volcanoes.

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“…Pyroclastic currents – or Pyroclastic Density Currents (PDCs) – are ground‐hugging flows made up of a mixture of pyroclasts comprising juvenile volcanic clasts and non‐juvenile, entrained ‘lithics’ that are partly supported by a gas phase, mainly entrained air (e.g. Druitt, 1998; Burgisser et al., 2005; Sulpizio & Dellino, 2008; Dufek, 2016; Lube et al., 2020). Deposits from PDCs encompass a wide range of grain sizes from fine ash (silt size and below), coarse ash (any sand size), lapilli (granule and pebble size) or bombs/blocks (boulder size).…”

Section: Introductionmentioning

confidence: 99%