Plate tephra: Preserved bubble walls from large slug bursts during violent Strombolian eruptions

Dawn C.S Ruth,Eliza S Calder

doi:10.1130/g34859.1

Abstract

Research Article| January 01, 2014 Plate tephra: Preserved bubble walls from large slug bursts during violent Strombolian eruptions Dawn C.S. Ruth; Dawn C.S. Ruth * 1Department of Geology, 411 Cooke Hall, State University of New York University at Buffalo, Buffalo, New York 14260, USA *E-mail: dcs34@buffalo.edu. Search for other works by this author on: GSW Google Scholar Eliza S. Calder Eliza S. Calder 1Department of Geology, 411 Cooke Hall, State University of New York University at Buffalo, Buffalo, New York 14260, USA2School of Geosciences, Grant Institute, University of Edinburgh, The King’s Buildings, West Mains Road, Edinburgh EH9 3JW, UK Search for other works by this author on: GSW Google Scholar Geology (2014) 42 (1): 11–14. https://doi.org/10.1130/G34859.1 Article history received: 20 Jun 2013 rev-recd: 09 Sep 2013 accepted: 10 Sep 2013 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Dawn C.S. Ruth, Eliza S. Calder; Plate tephra: Preserved bubble walls from large slug bursts during violent Strombolian eruptions. Geology 2014;; 42 (1): 11–14. doi: https://doi.org/10.1130/G34859.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We describe unusual “plate tephra” particles that provide key information about rarely observed processes that occur during volcanic eruptions. The tephra formed during the 2008–2009 eruption of Llaima volcano, Chile, and dispersed as far as 9 km from the vent. The plates are angular clasts of vesicular basaltic andesite ranging in size from 1 to 14 cm and in thickness from 2 to 5 mm. External features such as ridges, varying degrees of curvature, and adhered material are present. Internal textures include strong crystal alignment and deformed enclaves. We propose that the plates are wall fragments formed during the rupture of large gas slugs associated with unsteady fire fountaining during the violent Strombolian phase of the eruption. The presence of plate tephra may be a diagnostic feature of highly unsteady activity where slug rupture is concurrent with the formation of a sustained eruption column. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Highlights

Distinct vesicular, basaltic andesite plates produced during the violentStrombolian opening phase of the 2008–2009 eruption of Llaima volcano, Chile, are investigated
We characterize an uncommonly reported type of plate-shaped tephra produced during a violent Strombolian eruption at Llaima volcano
Textural and video observations we infer the plates are formed by thinning and extension of a magma film, followed by inertial fragmentation as large gas slugs emanate from the conduit and rupture above the vent

Summary

INTRODUCTION

Strombolian opening phase of the 2008–2009 eruption of Llaima volcano, Chile, are. investigated. We interpret the distinct shape of the plates, as well as internal textures, as caused by extensional thinning of a magma film originating as walls of large slugs (several to tens of meters in diameter) (Fig. 5a) In this model, expanding bubbles, near or above the vent, experience film thinning, ductile deformation, and undergo a primary phase of inertial fragmentation, generating large, possibly sheet-shaped tatters of magma. In this context plates can be a useful diagnostic feature of highly unsteady violent Strombolian eruptions Based on their planar shape and similar densities to the scoria, we infer the plates had a lower fall velocity, as a function of increased surface drag and chaotic fall behavior (e.g., tumbling and fluttering) (Foshag and González, 1956; Wilson and Huang, 1979; Andersen et al, 2005; Pioli et al, 2008). The cross-wind distribution of plates in the deposit was limited with respect to the scoria; this likely relates to the complex interaction of the plates with the wind field, such as possibly the decoupling from the plume at lower heights

CONCLUSIONS

Figures and Video