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Rootless tephra stratigraphy and emplacement processes

Volcanic rootless cones are the products of thermohydraulic explosions involving rapid heat transfer from active lava (fuel) to external sources of water (coolant). Rootless eruptions are attributed to molten fuel–coolant interactions (MFCIs), but previous studies have not performed systematic inves...

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Autores principales: Hamilton, Christopher W., Fitch, Erin P., Fagents, Sarah A., Thordarson, Thorvaldur
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Berlin Heidelberg 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7115078/
https://www.ncbi.nlm.nih.gov/pubmed/32269405
http://dx.doi.org/10.1007/s00445-016-1086-4
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author Hamilton, Christopher W.
Fitch, Erin P.
Fagents, Sarah A.
Thordarson, Thorvaldur
author_facet Hamilton, Christopher W.
Fitch, Erin P.
Fagents, Sarah A.
Thordarson, Thorvaldur
author_sort Hamilton, Christopher W.
collection PubMed
description Volcanic rootless cones are the products of thermohydraulic explosions involving rapid heat transfer from active lava (fuel) to external sources of water (coolant). Rootless eruptions are attributed to molten fuel–coolant interactions (MFCIs), but previous studies have not performed systematic investigations of rootless tephrostratigraphy and grain-size distributions to establish a baseline for evaluating relationships between environmental factors, MFCI efficiency, fragmentation, and patterns of tephra dispersal. This study examines a 13.55-m-thick vertical section through an archetypal rootless tephra sequence, which includes a rhythmic succession of 28 bed pairs. Each bed pair is interpreted to be the result of a discrete explosion cycle, with fine-grained basal material emplaced dominantly as tephra fall during an energetic opening phase, followed by the deposition of coarser-grained material mainly as ballistic ejecta during a weaker coda phase. Nine additional layers are interleaved throughout the stratigraphy and are interpreted to be dilute pyroclastic density current (PDC) deposits. Overall, the stratigraphy divides into four units: unit 1 contains the largest number of sediment-rich PDC deposits, units 2 and 3 are dominated by a rhythmic succession of bed pairs, and unit 4 includes welded layers. This pattern is consistent with a general decrease in MFCI efficiency due to the depletion of locally available coolant (i.e., groundwater or wet sediments). Changing conduit/vent geometries, mixing conditions, coolant and melt temperatures, and/or coolant impurities may also have affected MFCI efficiency, but the rhythmic nature of the bed pairs implies a periodic explosion process, which can be explained by temporary increases in the water-to-lava mass ratio during cycles of groundwater recharge. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00445-016-1086-4) contains supplementary material, which is available to authorized users.
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spelling pubmed-71150782020-04-06 Rootless tephra stratigraphy and emplacement processes Hamilton, Christopher W. Fitch, Erin P. Fagents, Sarah A. Thordarson, Thorvaldur Bull Volcanol Research Article Volcanic rootless cones are the products of thermohydraulic explosions involving rapid heat transfer from active lava (fuel) to external sources of water (coolant). Rootless eruptions are attributed to molten fuel–coolant interactions (MFCIs), but previous studies have not performed systematic investigations of rootless tephrostratigraphy and grain-size distributions to establish a baseline for evaluating relationships between environmental factors, MFCI efficiency, fragmentation, and patterns of tephra dispersal. This study examines a 13.55-m-thick vertical section through an archetypal rootless tephra sequence, which includes a rhythmic succession of 28 bed pairs. Each bed pair is interpreted to be the result of a discrete explosion cycle, with fine-grained basal material emplaced dominantly as tephra fall during an energetic opening phase, followed by the deposition of coarser-grained material mainly as ballistic ejecta during a weaker coda phase. Nine additional layers are interleaved throughout the stratigraphy and are interpreted to be dilute pyroclastic density current (PDC) deposits. Overall, the stratigraphy divides into four units: unit 1 contains the largest number of sediment-rich PDC deposits, units 2 and 3 are dominated by a rhythmic succession of bed pairs, and unit 4 includes welded layers. This pattern is consistent with a general decrease in MFCI efficiency due to the depletion of locally available coolant (i.e., groundwater or wet sediments). Changing conduit/vent geometries, mixing conditions, coolant and melt temperatures, and/or coolant impurities may also have affected MFCI efficiency, but the rhythmic nature of the bed pairs implies a periodic explosion process, which can be explained by temporary increases in the water-to-lava mass ratio during cycles of groundwater recharge. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00445-016-1086-4) contains supplementary material, which is available to authorized users. Springer Berlin Heidelberg 2017-01-10 2017 /pmc/articles/PMC7115078/ /pubmed/32269405 http://dx.doi.org/10.1007/s00445-016-1086-4 Text en © The Author(s) 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
spellingShingle Research Article
Hamilton, Christopher W.
Fitch, Erin P.
Fagents, Sarah A.
Thordarson, Thorvaldur
Rootless tephra stratigraphy and emplacement processes
title Rootless tephra stratigraphy and emplacement processes
title_full Rootless tephra stratigraphy and emplacement processes
title_fullStr Rootless tephra stratigraphy and emplacement processes
title_full_unstemmed Rootless tephra stratigraphy and emplacement processes
title_short Rootless tephra stratigraphy and emplacement processes
title_sort rootless tephra stratigraphy and emplacement processes
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7115078/
https://www.ncbi.nlm.nih.gov/pubmed/32269405
http://dx.doi.org/10.1007/s00445-016-1086-4
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