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Bulletin of Volcanology

, Volume 74, Issue 5, pp 1057–1082 | Cite as

Dynamics, stratigraphy and proximal dispersal of supraglacial tephra during the ice-confined 2004 eruption at Grímsvötn Volcano, Iceland

  • T. C. Jude-Eton
  • T. Thordarson
  • M. T. Gudmundsson
  • B. Oddsson
Research Article

Abstract

The basaltic, phreatomagmatic eruption of Grímsvötn volcano, Iceland, in November 2004 (G2004) lasted for 5 days, during which time two separate vents were active. Significant deposition of tephra occurred in the first 45 h only. We have subdivided the deposit into seven units (A–G) on the basis of differences in texture, grain size and componentry, and the presence of sharp contacts between the layers. The distribution of tephra lobes was used to infer the vent of origin for each unit. The G2004 deposit is poorly sorted overall and consists of non-vesicular to highly vesicular juvenile components. Units A and B comprise almost exclusively non- to poorly vesicular glass fragments, whereas units C–G contain at least 30 vol.% highly vesicular pumice. The proportion of non-juvenile fragments increases significantly in the final unit (unit F) of the main phase; non-juvenile fragments are restricted to the coarse (>0 Φ) fraction of the deposit. Main phase units C and E account for 80% of the total deposit volume, including the entire distal portion, and are interpreted to represent a mixture of (1) a widely dispersed component that fell from the upper margins of a strongly inclined (∼45°), 6–10 km high plume and (2) a locally dispersed (<3 km from source) component originating from pyroclastic density currents and minor tephra jets.

Keywords

Grímsvötn Glacio-volcanism Tephra dispersal Phreatomagmatic Basalt Explosive eruption 

Notes

Acknowledgments

The authors gratefully acknowledge the support of the following agencies and individuals, without the help of whom this work would not have been possible: A RANNÍS grant covered analytical and fieldwork costs; TC Jude-Eton received a Rannsóknanámssjóður studentship and another from the University of Edinburgh; JÖRFÍ (the Icelandic Glaciological Society) provided equipment, expertise and assistance in the field. The manuscript was vastly improved by the insightful reviews of Ármann Höskuldsson, Jocelyn McPhie and Ian Skilling.

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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • T. C. Jude-Eton
    • 1
  • T. Thordarson
    • 1
  • M. T. Gudmundsson
    • 2
  • B. Oddsson
    • 2
  1. 1.School of GeoSciencesUniversity of EdinburghEdinburghUK
  2. 2.Institute of Earth SciencesUniversity of IcelandReykjavíkIceland

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