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

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1130/G50169.1. This is version 3 of this Preprint.

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Authors

Natasha Joanne Dowey , Rebecca Williams 

Abstract

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.

DOI

https://doi.org/10.31223/osf.io/gah85

Subjects

Earth Sciences, Physical Sciences and Mathematics, Volcanology

Keywords

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

Dates

Published: 2020-05-24 22:23

Last Updated: 2022-05-25 04:13

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License

CC BY Attribution 4.0 International

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