Formation of Ice-Block Obstacle Marks during the November 1996 Glacier-Outburst Flood (Jökulhlaup), Skeiðarársandur, Southern Iceland

  1. I. Peter Martini2,
  2. Victor R. Baker3 and
  3. Guillermina Garzón4
  1. H. Fay

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304299.ch6

Flood and Megaflood Processes and Deposits: Recent and Ancient Examples

Flood and Megaflood Processes and Deposits: Recent and Ancient Examples

How to Cite

Fay, H. (2002) Formation of Ice-Block Obstacle Marks during the November 1996 Glacier-Outburst Flood (Jökulhlaup), Skeiðarársandur, Southern Iceland, in Flood and Megaflood Processes and Deposits: Recent and Ancient Examples (eds I. P. Martini, V. R. Baker and G. Garzón), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304299.ch6

Editor Information

  1. 2

    Department of Land Resource Science, University of Guelph, Guelph, Ontario, Canada

  2. 3

    Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721–0011, USA

  3. 4

    Dpto de Geodinámica, Fac. de Geología, Universidad of Complutense, 28040 Madrid, Spain

Author Information

  1. Earth Surface Processes Research Group, School of Earth Sciences and Geography, Keele University, Keele, Staffordshire ST5 5BG, UK

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 10 FEB 2002

ISBN Information

Print ISBN: 9780632064045

Online ISBN: 9781444304299

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Keywords:

  • formation of ice-block obstacle marks during November 1996 glacier-outburst flood (jökulhlaup), Skeiðarársandur, southern Iceland;
  • impact of ice blocks on proglacial outwash plains;
  • interpretation and discussion;
  • newly identified obstacle marks interpreted as ‘kettle-scours’ - formed by flood flow and in situ melting of ice blocks after floods recede;
  • glacier outburst floods or ‘jökulhlaups’ - involving transport of ice blocks released from glacier margins

Summary

Glacier outburst floods or ‘jökulhlaups’ commonly involve the transport of ice blocks released from glacier margins. Very few published studies have focused on the effects of ice blocks on outwash plains during and following jökulhlaups. A volcanic eruption beneath the Vatnajökull ice-cap in southern Iceland generated a jökulhlaup on 5 November 1996 that transported numerous ice blocks as large as 45 m in diameter on to Skeiðarársandur. The morphology and sedimentology of a series of large, coarse grained bedforms formed around large stranded ice blocks during the November 1996 jökulhlaup are examined in relation to flow conditions.

Ice-block obstacle marks were formed both by scour during the flow and by in situ melting after the flood receded. Flow separation around ice blocks resulted in the lee of the blocks becoming a locus of rapid deposition and led to the formation of entirely aggradational obstacle shadows. Flow around ice blocks also resulted in the deposition of upstream-dipping strata in sets up to 4 m thick that are interpreted as antidune stoss sides. Evidence of deposition from traction carpets during both rising and waning stages of the flood was preserved around ice blocks. It is suggested that the 1996 jökulhlaup flow was predominantly subcritical, but that locally flow became supercritical around ice blocks.