The geomorphic impact and sedimentary characteristics of the July 1999 jökulhlaup on the Jökulsá á Sólheimasandi, Mýrdalsjökull, southern Iceland

Few studies have focused on the geomorphic and sedimentary impact of magmatically-generated jôkulhlaups released directly into the proglacial zone. This paper characterizes the proglacial geomorphic and sedimentary impact of the 17-18 July 1999 jôkulhlaup, Glacier Sôlheimajôkull, Iceland.
Jôkulhlaup outflow from the glacier margin resulted in temporary water storage within former ice-dammed lake basins, resulting in the deposition of coarsegrained 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 Mount Katla eruption.

Key words: Jôkulsâ â Sôlheimasandi; Myrdalsjôkull; Iceland; geomorphological impact; ice blocks; temporary storage; outwash fan; proglacial; Katla; boulders