A bedform phase diagram for dense granular currents

Pyroclastic density currents (PDCs) are a life-threatening volcanic hazard. Our understanding and hazard assessments of these flows rely on interpretations of their deposits. The occurrence of stratified layers, cross-stratification, and bedforms in these deposits has been assumed as indicative of d...

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Bibliographic Details
Published in:Nature communications 2020-06, Vol.11 (1), p.2873-2873, Article 2873
Main Authors: Smith, Gregory, Rowley, Peter, Williams, Rebecca, Giordano, Guido, Trolese, Matteo, Silleni, Aurora, Parsons, Daniel R., Capon, Samuel
Format: Article
Language:English
Subjects:
704/2151/3930
704/2151/598
704/4111
Aeration
Density currents
Deposits
Environmental science
Experiments
Fluid dynamics
Geological hazards
Hazard assessment
Humanities and Social Sciences
Morphology
multidisciplinary
Outcrops
Phase diagrams
Science
Science (multidisciplinary)
Sedimentary structures
Supercritical flow
Volcanic activity
Volcanoes
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Summary:Pyroclastic density currents (PDCs) are a life-threatening volcanic hazard. Our understanding and hazard assessments of these flows rely on interpretations of their deposits. The occurrence of stratified layers, cross-stratification, and bedforms in these deposits has been assumed as indicative of dilute, turbulent, supercritical flows causing traction-dominated deposition. Here we show, through analogue experiments, that a variety of bedforms can be produced by denser, aerated, granular currents, including backset bedforms that are formed in waning flows by an upstream-propagating granular bore. We are able to, for the first time, define phase fields for the formation of bedforms in PDC deposits. We examine how our findings impact the understanding of bedform features in outcrop, using the example of the Pozzolane Rosse ignimbrite of the Colli Albani volcano, Italy, and thus highlight that interpretations of the formative mechanisms of these features observed in the field must be reconsidered. In this study, Smith and colleagues employ analogue experiments to show the controlling parameters on sediment bedforms in pyroclastic density current deposits. The findings are applied and validated on natural deposits.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-020-16657-z