The role of multiple glacier outburst floods in proglacial landscape evolution: The 2010 Eyjafjallajokull eruption, Iceland

The 2010 Eyjafjallajokull eruption in Iceland provided a unique opportunity to quantify the evolution of proglacial geomorphology during a series of volcanogenic jokulhlaups (glacial outburst floods) (>140 events). Time-lapse imagery and repeat terrestrial laser scans before and directly after the eruption show that the jokulhlaup of 14 April 2010 composed 61% of the 57 x 10(6) m(3) total discharge of the combined events, and had the highest peak discharge for the two main flood events, but only deposited 18% of the total volume of sediment in front of Gigjokull glacier. The majority of sediments (67% of a total volume of 17.12 x 10(6) m(3)) were deposited by the 15 April 2010 jokulhlaup, and this was followed by extensive reworking by a series of smaller jokulhlaups over the following 29 days that deposited 15% of the total sediment. The geomorphological and sedimentary signatures of the two largest jokulhlaups associated with the onset of the eruption have either been reworked by later floods or are buried by later flood deposits. Consequently, the ice-proximal, posteruption landscape cannot be used to reconstruct the characteristics or magnitudes of either of the two largest jokulhlaups. The findings support a complex-response model in which peak discharge and the bulk of the sediment transported is decoupled by changing routing mechanisms and water: sediment ratios during the eruption.