Impact of the July 1999 jökulhlaup on the proximal River Jökulsá á Sólheimasandi, Mýrdalsjökull Glacier, southern Iceland

Russell, AJ; Tweed, FS; Knudsen, Ó; Roberts, MJ; Harris, TD; Marren, PM

Impact of the July 1999 jökulhlaup on the proximal River Jökulsá á Sólheimasandi, Mýrdalsjökull Glacier, southern Iceland

Lookup NU author(s): Professor Andrew Russell ORCiD

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Abstract

Few studies have focused on the geomorphic and sedimentary impact of magmatically-generated jökulhlaups released directly into the proglacial zone. This paper characterizes the proglacial geomorphic and sedimentary impact of the 17-18 July 1999 jökulhlaup, Sólheimajökull, Iceland. Jökulhlaup outflow from the glacier margin resulted in temporary water storage within former ice-dammed lake basins, resulting in the deposition of coarse-grained deltas, and more distal sandy bedforms capped by silts. Outflow from the western outlet transported boulders up to 8 m in diameter on the surface of a new outwash fan ranging in thickness from 6 m proximally to 1 m distally. Near-simultaneous deposition of ice blocks, boulders and finer-grained matrix occurred, suggesting that flows were sediment rich during the rising stage of the flood. This unexpected short-lived flood had a distinctive impact on the proglacial zone, providing a record of a precursor to a Katla eruption.