Simultaneous fall and flow during pyroclastic eruptions: a novel proximal hybrid facies.

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Natasha Joanne Dowey , Rebecca Williams 


The deposits of Plinian and sub-Plinian eruptions provide critical insights into past volcanic events and inform numerical models that aim to mitigate against future hazards. However, pyroclastic deposits are often considered from either a fallout or pyroclastic density current (PDC) perspective, with little attention given to facies exhibiting characteristics of both processes. Such hybrid units may be created where fallout and PDCs act simultaneously, where a transitional phase between the two occurs, and/or due to reworking. This study presents analysis of a novel hybrid pyroclastic lithofacies found on Tenerife and Pantelleria. The coarse pumice block facies has an openwork texture and correlates with distal Plinian units, but is cross-stratified and relatively poorly sorted with an erosional base. The facies is proposed to record the simultaneous interaction of very proximal fallout with turbulent PDCs, and reveals a fuller spectrum of hybrid deposition than previously reported. This work highlights the importance of recognising hybrid deposition both in the rock record and hazard modelling.



Earth Sciences, Physical Sciences and Mathematics, Volcanology


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


Published: 2020-05-24 22:23

Last Updated: 2022-05-25 04:13

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CC BY Attribution 4.0 International

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