Tunnel channel formation during the November 1996 jökulhlaup, Skeiðarárjökull, Iceland

  1. Lookup NU author(s)
  2. Professor Andrew Russell
  3. Dr Andy Large
Author(s)Russell AJ, Gregory AG, Large ARG, Fleisher PJ, Harris T
Publication type Article
JournalAnnals of Glaciology
ISSN (print)0260-3055
ISSN (electronic)1727-5644
Full text is available for this publication:
Despite the ubiquity of tunnel channels and valleys within formerly glaciated areas, their origin remains enigmatic. Few modern analogues exist for event-related subglacial erosion. This paper presents evidence of subglacial meltwater erosion and tunnel channel formation during the November 1996 jökulhlaup, Skeiðarárjökull, Iceland. The jökulhlaup reached a peak discharge of 45,000 – 50,000 m 3 s -1 , with flood outbursts emanating from multiple outlets across the entire 23 km wide glacier snout. Subsequent retreat of the south-eastern margin of Skeiðarárjökull has revealed a tunnel channel excavated into the surrounding moraine sediment and ascending 11.5 m over a distance of 160 m from a larger trough to join the apex of an ice-contact fan formed in November 1996. The tunnel channel formed via hydro- mechanical erosion of 14,000 m 3 - 24,000 m 3 of unconsolidated glacier substrate, evidenced by copious rip-up clasts within the ice-contact fan. Flow reconstruction provides peak discharge estimates of 683 m 3 s -1. The tunnel channel orientation, oblique to local ice flow direction nd within a col, suggests that local jökulhlaup routing was controlled by (a) subglacial topography and (b)the presence of a nearby proglacial lake. We describe the first modern example of tunnel channel formation and illustrate the importance of pressurised subglacial jökulhlaup flow for tunnel channel formation.
PublisherInternational Glaciological Society
Actions    Link to this publication