New understanding of hybrid pyroclastic processes revealed from proximal deposits: implications for uncertainty in volcanic hazard assessment

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Natasha Joanne Dowey , Rebecca Williams 


The deposits of Plinian and sub-Plinian eruptions provide critical insights into the behaviour and magnitude of past volcanic events, and inform numerical models that aim to mitigate against future volcanic hazards. However, pyroclastic deposits are often considered from either a fallout or flow perspective, with relatively little attention given to the complex spectrum of hybrid processes that occur between the two end members. This study provides new analysis of hybrid deposits generated by a combination of fallout from a Plinian/sub-Plinian plume and pyroclastic density current (flow) activity. We review previously reported hybrid lithofacies, present a novel lithofacies found on Tenerife and Pantelleria, and bring together a synthesis of hybrid processes as we currently understand them. The lithofacies reported here is a cross stratified pumice block tuff that records interaction between coarse fallout and pyroclastic density currents proximal (<5km) to the vent. Many hybrid lithofacies are likely misidentified or are cryptic in the rock record; improved consideration of these complex processes both in the field and in modelling will improve our understanding of the uncertainties inherent in the analysis of pyroclastic successions, therefore improving our analysis of eruption characteristics and volcanic hazards.



Earth Sciences, Physical Sciences and Mathematics, Volcanology


plinian fallout; pyroclastic density currents; hybrid deposition; stratigraphic analysis; volcanic hazards


Published: 2020-05-24 19:23


CC BY Attribution 4.0 International

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