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Breard ECP, Dufek J, Charbonnier S, Gueugneau V, Giachetti T, Walsh B. The fragmentation-induced fluidisation of pyroclastic density currents. Nat Commun 2023; 14:2079. [PMID: 37045849 PMCID: PMC10097808 DOI: 10.1038/s41467-023-37867-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 03/29/2023] [Indexed: 04/14/2023] Open
Abstract
Pyroclastic density currents (PDCs) are the most lethal volcanic process on Earth. Forecasting their inundation area is essential to mitigate their risk, but existing models are limited by our poor understanding of their dynamics. Here, we explore the role of evolving grain-size distribution in controlling the runout of the most common PDCs, known as block-and-ash flows (BAFs). Through a combination of theory, analysis of deposits and experiments of natural mixtures, we show that rapid changes of the grain-size distribution transported in BAFs result in the reduction of pore volume (compaction) within the first kilometres of their runout. We then use a multiphase flow model to show how the compressibility of granular mixtures leads to fragmentation-induced fluidisation (FIF) and excess pore-fluid pressure in BAFs. This process dominates the first ~2 km of their runout, where the effective friction coefficient is progressively reduced. Beyond that distance, transport is modulated by diffusion of the excess pore pressure. Fragmentation-induced fluidisation provides a physical basis to explain the decades-long use of low effective friction coefficients used in depth-averaged simulations required to match observed flow inundation.
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Affiliation(s)
- Eric C P Breard
- School of Geosciences, University of Edinburgh, Edinburgh, UK.
- Department of Earth Sciences, University of Oregon, Eugene, OR, USA.
| | - Josef Dufek
- Department of Earth Sciences, University of Oregon, Eugene, OR, USA
| | | | | | - Thomas Giachetti
- Department of Earth Sciences, University of Oregon, Eugene, OR, USA
| | - Braden Walsh
- Centre for Natural Hazards Research, Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada
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Phase partitioning during fragmentation revealed by QEMSCAN Particle Mineralogical Analysis of volcanic ash. Sci Rep 2019; 9:126. [PMID: 30644409 PMCID: PMC6333781 DOI: 10.1038/s41598-018-36857-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 11/23/2018] [Indexed: 11/08/2022] Open
Abstract
Volcanic ash particle properties depend upon their genetic fragmentation processes. Here, we introduce QEMSCAN Particle Mineralogical Analysis (PMA) to quantify the phase distribution in ash samples collected during activity at Santiaguito, Guatemala and assess the fragmentation mechanisms. Volcanic ash from a vulcanian explosion and from a pyroclastic density current resulting from a dome collapse were selected. The ash particles resulting from both fragmentation modes are dense and blocky, typical of open-vent dome volcanoes and have a componentry consistent with their andesitic composition. We use image analysis to compare the fraction of each phase at particle boundaries compared to the total particle fraction. Our results show that the explosion-derived ash has an even distribution of plagioclase and glass, but boundaries enriched in pyroxene and amphibole. In contrast, the ash generated during dome collapse has an increased fraction of glass and decreased fraction of plagioclase at particle boundaries, suggesting that fractures preferentially propagate through glass during abrasion and milling in pyroclastic flows. This study presents QEMSCAN PMA as a new resource to identify generation mechanisms of volcanic ash, which is pertinent to volcanology, aviation, respiratory health and environmental hazards, and highlights the need for further experimental constraints on the fragmentation mechanism fingerprint.
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Jones TJ, Russell JK. Attrition in the kimberlite system. MINERALOGY AND PETROLOGY 2018; 112:491-501. [PMID: 30880876 PMCID: PMC6394374 DOI: 10.1007/s00710-018-0580-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 04/20/2018] [Indexed: 06/09/2023]
Abstract
The sustained transportation of particles in a suspension commonly results in particle attrition leading to grain size reduction and shape modification. Particle attrition is a well-studied phenomenon that has mainly focussed on sediments produced in aeolian or fluvial environments. Here, we present analogue experiments designed to explore processes of attrition in the kimberlite system; we focus on olivine as it is the most abundant constituent of kimberlite. The attrition experiments on olivine use separate experimental set-ups to approximate two natural environments relevant to kimberlites. Tumbling mill experiments feature a low energy system supporting near continual particle-particle contact and are relevant to re-sedimentation and dispersal processes. Experiments performed in a fluidized particle bed constitute a substantially higher energy environment pertinent to kimberlite ascent and eruption. The run-products of each experiment are analysed for grain size reduction and shape modification and these data are used to elucidate the rates and extents of olivine attrition as a function of time and energy. Lastly, we model the two experimental datasets with an empirical rate equation that describes the production of daughter products (fines) with time. Both datasets approach a fines production limit, or plateau, at long particle residence times; the fluidized system is much more efficient producing a substantially higher fines content and reaches the plateau faster. Our experimental results and models provide a way to forensically examine a wide range of processes relevant to kimberlite on the basis of olivine size and shape properties.
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Affiliation(s)
- Thomas J. Jones
- Department of Earth Sciences, Durham University, South Road, Durham, DH1 3LE UK
- Department of Geosciences, University of Tuebingen, Wilhelmstrasse 56, 72074 Tuebingen, Germany
| | - James K. Russell
- Department of Earth, Ocean & Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4 Canada
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Abstract
Tephra deposits result from explosive volcanic eruption and serve as indirect probes into fragmentation processes operating in subsurface volcanic conduits. Primary magmatic fragmentation creates a population of pyroclasts through volatile-driven decompression during conduit ascent. In this study, we explore the role that secondary fragmentation, specifically attrition, has in transforming primary pyroclasts upon transport in volcanic conduits and plumes. We utilize total grain size distributions from a suite of natural and experimentally produced tephra to show that attrition is likely to occur in all explosive volcanic eruptions. Our experimental results indicate that fine ash production and surface area generation is fast (<15 min) thereby rapidly raising the fractal dimension of tephra deposits. Furthermore, a new metric, the Entropy of Information, is introduced to quantify the degree of attrition (secondary fragmentation) from grain size data. Attrition elevates fine ash production which, in turn, has consequences for eruption column stability, tephra dispersal, aggregation, volcanic lightening generation, and has concomitant effects on aviation safety and Earth's climate.
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Jutzeler M, Marsh R, Carey RJ, White JDL, Talling PJ, Karlstrom L. On the fate of pumice rafts formed during the 2012 Havre submarine eruption. Nat Commun 2014; 5:3660. [PMID: 24755668 PMCID: PMC3997806 DOI: 10.1038/ncomms4660] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 03/14/2014] [Indexed: 11/29/2022] Open
Abstract
Pumice rafts are floating mobile accumulations of low-density pumice clasts generated by silicic volcanic eruptions. Pumice in rafts can drift for years, become waterlogged and sink, or become stranded on shorelines. Here we show that the pumice raft formed by the impressive, deep submarine eruption of the Havre caldera volcano (Southwest Pacific) in July 2012 can be mapped by satellite imagery augmented by sailing crew observations. Far from coastal interference, the eruption produced a single >400 km2 raft in 1 day, thus initiating a gigantic, high-precision, natural experiment relevant to both modern and prehistoric oceanic surface dispersal dynamics. Observed raft dispersal can be accurately reproduced by simulating drift and dispersal patterns using currents from an eddy-resolving ocean model hindcast. For future eruptions that produce potentially hazardous pumice rafts, our technique allows real-time forecasts of dispersal routes, in addition to inference of ash/pumice deposit distribution in the deep ocean. Pumice rafts result from volcanic eruptions into and onto water, and can be extensive and potentially hazardous, but tracking their dispersal is difficult. Jutzeler et al. combine satellite imagery and an ocean model to accurately forecast pumice raft dispersal routes.
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Affiliation(s)
- Martin Jutzeler
- 1] National Oceanography Centre, Southampton, European Way, Southampton SO14 3ZH, UK [2] Department of Geology, University of Otago, PO Box 56, Dunedin 9056, New Zealand
| | - Robert Marsh
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, European Way, Southampton SO14 3ZH, UK
| | - Rebecca J Carey
- CODES-ARC Centre of Excellence in Ore Deposits, University of Tasmania, PO Box 79, Hobart 7005, Australia
| | - James D L White
- Department of Geology, University of Otago, PO Box 56, Dunedin 9056, New Zealand
| | - Peter J Talling
- National Oceanography Centre, Southampton, European Way, Southampton SO14 3ZH, UK
| | - Leif Karlstrom
- Department of Geophysics, Stanford University, 397 Panama Mall, Stanford California 94305, USA
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Douillet GA, Tsang-Hin-Sun È, Kueppers U, Letort J, Pacheco DA, Goldstein F, Von Aulock F, Lavallée Y, Hanson JB, Bustillos J, Robin C, Ramón P, Hall M, Dingwell DB. Sedimentology and geomorphology of the deposits from the August 2006 pyroclastic density currents at Tungurahua volcano, Ecuador. BULLETIN OF VOLCANOLOGY 2013; 75:765. [PMID: 26069386 PMCID: PMC4456066 DOI: 10.1007/s00445-013-0765-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 09/20/2013] [Indexed: 06/04/2023]
Abstract
The deposits of the pyroclastic density currents from the August 2006 eruption of Tungurahua show three facies associations depending on the topographic setting: the massive, proximal cross-stratified, and distal cross-stratified facies. (1) The massive facies is confined to valleys on the slopes of the volcano. It contains clasts of >1 m diameter to fine ash material, is massive, and interpreted as deposited from dense pyroclastic flows. Its surface can exhibit lobes and levees covered with disk-shaped and vesicular large clasts. These fragile large clasts must have rafted at the surface of the flows all along the path in order to be preserved, and thus imply a sharp density boundary near the surface of these flows. (2) The proximal cross-stratified facies is exposed on valley overbanks on the upper part of the volcano and contains both massive coarse-grained layers and cross-stratified ash and lapilli bedsets. It is interpreted as deposited from (a) dense pyroclastic flows that overflowed the gentle ridges of valleys of the upper part of the volcano and (b) dilute pyroclastic density currents created from the dense flows by the entrainment of air on the steep upper flanks. (3) The distal cross-stratified facies outcrops as spatially limited, isolated, and wedge-shaped bodies of cross-stratified ash deposits located downstream of cliffs on valleys overbanks. It contains numerous aggrading dune bedforms, whose crest orientations reveal parental flow directions. A downstream decrease in the size of the dune bedforms, together with a downstream fining trend in the grain size distribution are observed on a 100-m scale. This facies is interpreted to have been deposited from dilute pyroclastic density currents with basal tractional boundary layers. We suggest that the parental flows were produced from the dense flows by entrainment of air at cliffs, and that these diluted currents might rapidly deposit through "pneumatic jumps". Three modes are present in the grain size distribution of all samples independently of the facies, which further supports the interpretation that all three facies derive from the same initial flows. This study emphasizes the influence of topography on small volume pyroclastic density currents, and the importance of flow transformation and flow-stripping processes.
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Affiliation(s)
- Guilhem Amin Douillet
- Earth & Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany
- Ecole et Observatoire des Sciences de la Terre, Université de Strasbourg, Strasbourg, France
- Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador
- Institut de Recherche pour le Développement, UMR volcan, Quito, Ecuador
| | - Ève Tsang-Hin-Sun
- Ecole et Observatoire des Sciences de la Terre, Université de Strasbourg, Strasbourg, France
- Laboratoire de Géosciences Marines, Université de Brest, Plouzané, France
| | - Ulrich Kueppers
- Earth & Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany
| | - Jean Letort
- Ecole et Observatoire des Sciences de la Terre, Université de Strasbourg, Strasbourg, France
- Laboratoire de Géophysique Interne et Techtonophysique (LGIT), Grenoble, France
| | | | - Fabian Goldstein
- Earth & Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany
| | - Felix Von Aulock
- Earth & Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany
| | - Yan Lavallée
- Earth & Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany
| | | | - Jorge Bustillos
- Ecole et Observatoire des Sciences de la Terre, Université de Strasbourg, Strasbourg, France
| | - Claude Robin
- Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador
- Institut de Recherche pour le Développement, UMR volcan, Quito, Ecuador
| | - Patricio Ramón
- Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador
| | - Minard Hall
- Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador
| | - Donald B. Dingwell
- Earth & Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany
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Dufek J, Wexler J, Manga M. Transport capacity of pyroclastic density currents: Experiments and models of substrate-flow interaction. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jb006216] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Josef Dufek
- School of Earth and Atmospheric Sciences; Georgia Institute of Technology; Atlanta Georgia USA
| | - Jason Wexler
- Department of Earth and Planetary Science; University of California; Berkeley California USA
| | - Michael Manga
- Department of Earth and Planetary Science; University of California; Berkeley California USA
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